Five Thousand Fun-Filled Miles of Geology: The 1972 Larsen Geological Field Trip Adventure into the American Southwest
By Timothy Dalbey Phil Clymer Tim Carter
Introduction This adventure log has been created to inspire young geology students to travel and immerse themselves in real geology rather than read about it in books. It’s also meant for professors who grasp that field trips are the absolute best way to motivate students to get excited about the scientific study of the Earth. The text includes both discussions 1
of the geological features we encountered and personal remembrances of events and activities. This is a collaboration of three strangers that met on the infamous University of Cincinnati 1972 Geology 271 Demonstration Field Trip taught by Dr. Leonard Larsen. Those three are Tim Carter, Phil Clymer, and Tim Dalbey. Carter went on to become a custom home builder and media specialist while Clymer pursued geology as a career and Dalbey went on to earn a doctorate in archaeology. PHIL CLYMER content: this year is the 50th anniversary of a fondly remembered event in the academic lives of a small group of aspiring geologists at the University of Cincinnati in 1972. The Geology 271 Demonstration Field Trip was scheduled for a two week journey to the Four Corners area of the Southwest USA, but lasted 20 days. Tim Dalbey’s road log measured the distance traveled as 4,831 miles, and the trip itinerary included stops at the Grand Canyon, Bryce, Zion, Petrified Forest and numerous other national and state parks.
Phil beside yucca plant, Indian Gardens, top of inner gorge Grand Canyon. Photo by Leonard Larsen. TIM CARTER content: the field trip was led by Dr. Leonard Larsen, a seasoned geologist whose main focus was hard-rock, igneous and metamorphic geology. It was an immersive experience to a new geology student to put it mildly.
2
Spending two weeks looking at the exposed bedrock of the Southwest USA is one way to get a young geology student excited about the science. It can also be a humbling experience if you absorb the enormity of it as can happen walking into and out of the Grand Canyon. TIM DALBEY content: geology field road log narrative, graphics and photos barely touches on the depth, range and complexity of the earth’s dynamics and geochronology through parts of twelve states and nearly 5,000 miles. Dr. Larsen was the ideal teacher for this trip because he felt most at home at rock outcroppings. His mild manner and chortle laugh put all of us at ease in hours. It was a daunting challenge to take sixteen students on a cross-country geology field trip.
Dr. Leonard Larsen, in his native element, lecturing students from 1973 Southwest trip, seated on outcrop of tuffs from the eruption of Jemez Caldera. Photo by Phil Clymer. There was a meeting in the spring quarter prior to the field trip. Dr. Larsen gave a short talk about what we should expect and what would be expected of us. He gave some advice about equipment to take along, such as binoculars, field boots, camping gear, etc., and asked for volunteers to supply cars or trucks. The estimated cost of the trip was placed at $300. Three hundred for such a trip seems fictional now, but our greatest expense was gasoline and it was a whopping thirty six cents a gallon. This grouping of students consisted mainly of second-year geology majors, and most had taken only the five-hour Introduction to Geology class. Thus, most of us were strangers to each other. Clymer writes that, our assembly point was in a small parking lot adjacent to Old Tech, the home of U.C. Geology. Our entourage consisted of sixteen student participants; Ken Appel, Steve Berniius, LeRon Bielak, Tim Carter, Phil Clymer, Lon Cooper, Tim Dalbey, 3
Mike Fein, Dennis Gillespie, Jim Grotke, Mike Honnert, Tom Parker, Ken Paul, Joe Ulmschneider, Jack Wunder, and Helen Young, and the leader, Dr. Leonard Larsen.
Tim Carter in the Arizona Desert next to Big Red, These seventeen people were shoehorned into four vehicles:
UC Geology department’s red International Harvester station wagon nicknamed Big Red
Ken Apple’s powder blue pickup truck with a protective aluminum cap over the bed
Dr. Larsen’s beige Oldsmobile sedan
Helen Young’s Chevy Nova
The group left campus about 9:30 a.m. and the plan was to drive in shifts straight through to Albuquerque. Please note, road maps showing geological stops in New Mexico, Arizona, Utah, and Colorado are included at the end of this document. Carter remembers, Tuesday, September 5th, the day of departure all of us met on a muggy Cincinnati morning. I had a backpack with extra clothes, a sleeping bag, my single lens reflex 35mm camera, and the required notebook. My guess is my Dad drove me up and dropped me off as I have no memory walking from home with all this gear. I can’t remember anything Dr. Larsen must have said as he addressed us once everyone was there. At some point he talked about how important it was to make accurate sketches in our notebooks at all road stops. Photos give a false sense of security by themselves. There might be things you notice and draw in a notebook that you might not pick out of a photo months or years later. A sketch plus written notes about what you see at a road stop are best. 4
There were no cell phones in those days and our caravan lacked CB radios. Dr. Larsen said if you get separated in the caravan, go to the next town’s main post office and wait.
The group in Meteor Crater. I have no clue how this would have worked had a car fallen behind or broke down and the other three just kept motoring down the interstate highway at 70 mph! The beginning of the trip September 5th, 1972, Dalbey writes, we started at Cincinnati hoping to get to Albuquerque, New Mexico by September 6th. The first day we crossed four states (Ohio - west part), Indiana, Illinois, Missouri) and 200 million years of geologic history from the Ordovician to the end of the Pennsylvanian traveling through topography that had been glaciated in the Pleistocene. We headed west from the UC campus in Clifton to I-75 to get to I-74 (partly under construction also using U.S Hwy. 52) for Indianapolis, Indiana, crossing the Mill Creek Valley choked with the latest Wisconsin Miami Lobe glacial outwash (Tazewell and Cary tills) deposited in a channel 100 to 150 feet deep ca. 14 and 12.5 kyr ago. Then, heading northwest on I-74 passing through road cuts of late Ordovician (488-443 mya) that contain the palaeontologically famous Cincinnatian Series (451-443 mya), where some of the most fossiliferous invertebrate limestones in the world have been studied for over 175 years and represent over 470 genera, over 1,200 species from various tidal environments of marine shallow seas. The marine deposits include ca. 1,000 feet of 5
limestones, shales, marls and limey mudstones capped by glacial till and alluvium from three glaciers that made it into this part of Cincinnati, the Kansan, Illinoian and Wisconsinan. As we travel on I-74 we pass through outcrops of the Maysvillian Stage (Fairview, Bellevue, Corryville, Mt. Auburn sequences), and closer to Indiana we pass into the Richmondian Stage (Sunset/Oregonia, Waynesville, Liberty, Whitewater, Saluda sequences), last sequences occur in Indiana. The Ordovician outcrops along I74 almost to Indianapolis with a narrow band of Silurian before Indianapolis. The fossiliferous deposits are the result of the equatorial Iapetus oceanic sea shelves with shallow seas surrounding the north to northeast trending Cincinnati Arch (Lexington Platform). A structural uplift (anticline) east of the Illinois Basin, southeast of the Michigan Basin and west of the Appalachian Basin that was still present later during the Devonian. Meanwhile, the Taconic orogeny had risen to the east adding sediments to the Appalachian Basin (foreland basin), on the east side of the arch forcing uplift combined with Cambrian uplift from below as part of the southern platform of the North American craton (Laurentian land mass). The fossiliferous Cincinnatian Series represents marine bio-lithofacies deposits across peritidal shallow deposits, shallow subtidal facies, deep subtidal facies, to offshore facies with lagoon, shoal, barrier and inlet restricted zones. Invertebrate species of the "peritidal" shallow facies includes a sparse fauna of bryozoans, ostracods, brachiopods, stromatoporoids, ripples, burrows and desiccation cracks of the Saluda formation in Indiana. Common invertebrates of the shallow subtidal facies include thicker shelled brachiopods: Platystrophia sp., Herbertella sp., Rafinesquina sp., bryozoan masses making up fossil hashes in the bioturbated low tide zone of the Bellevue, Mt. Auburn, Oregonia and Whitewater Formations. In the deep subtidal facies fossils include brachiopods and bryozoans ranging between the shallow subtidal. Offshore facies were deposited as storm beds with numerous trace fossils (holes, burrows and tracks) found in the Fairview, Corryville, Sunset and Liberty formations in Indiana. The offshore facies consist of thin skeletal crinoid grainstones deposited by possibly hurricane force storms with relatively small brachiopods Dalmanella sp., Sowerbyella sp., trilobites such as Flexicalymene sp. and Cryptolithus sp., plus other bryozoans, molluscs, with less breakage and numerous trace fossils common in the Waynesville Formation in Indiana. The marine fauna represents an "Ordovician Radiation" that went well beyond the "Cambrian Explosion" adding significantly more genera to the Phanerozoic marine bio-communities where carbonate (aragonite) shell secreting organisms attached to the shallow marine carbonate shelves. The uppermost fossiliferous Cincinnatian Series of marine invertebrates are found mostly in Indiana as we travel west on I-74 and represent a large marine mass extinction event affecting ca. 80-85 percent of the fauna. The first of the five major extinction events on the planet. Cold glacial conditions during the Hirnantian and temperature changes affected the marine environment, lowering epicontinental sea level, exposing shelf communities like those living on the "arch." This was followed by a long period of no deposition ca. 447-444 mya creating an unconformity before warm shallow seas of the Silurian inundated the shelf when the land mass was near the equator with a tropical climate and marine organisms flourished. Large reefs were common in the middle to late Silurian in the southwest with quiet areas like lagoons and 6
reefs where brachiopods, crinoids and corals lived in the shallow seas. Most of this bedrock is buried in the southwest. I-74 crosses the Whitewater River, another original north flowing Teays River in preglacial time that was clogged by glacial outwash that reversed the drainage to the Great Miami River, then on to the Ohio River. The Interstate roughly parallels the Shelbyville Moraine (ca. 21 kyr) of the Wisconsin Glacier over the flat Tipton Till Plain most of the way to Indianapolis overlying Brassfield Limestone bedrock that lies unconformably over Cincinnatian Series Ordovician bedrock. We got to Indianapolis at 10:40 AM after traveling 107 miles, then we headed for I-465 around the city to I-70 heading southwest towards Terre Haute, Indiana in the southwest corner of the state. Most of the topography of southwest Indiana along I-70 is relatively flat agricultural lands as a result of glaciation that left behind moraines, eskers and kames mostly from Illinoian glaciation that almost reached Terre Haute. At Terre Haute we crossed the Wabash River that was once part of the north draining catchment of the Teays River during preglacial times that became a major glacial outwash channel one to two miles wide and the largest northern tributary of the Ohio River Clymer, describes our First Stop as unscheduled in Indianapolis because one of the students discovered that his wallet was missing, and it was considered critical as it contained his field trip money. Was it lost, stolen, or forgotten? He called his wife to have her check if the wallet was on his desk. But she wasn’t yet home so we delayed an hour and a half for the call to be completed. Yes, it was on his desk. Larsen advanced LeRon the money for his trip expenses. Dalbey comments. From Indianapolis we traveled southwest crossing Devonian, Mississippian, and Pennsylvanian (Carboniferous) Paleozoic bedrock that was deposited offshore from the slope of the Cincinnati Arch into the Illinois Basin. The Paleozoic bedrock is mostly buried by glacial deposits to Terre Haute on I-70 to St. Louis, Missouri. Subsurface Devonian bedrock also reflects deposits from a shallow sea with diverse marine invertebrate fauna mostly of rugose and tabulate corals forming barrier reefs in a north to south orientation in a narrow basin. Sediments from the Cincinnati Arch built up and extended into deeper parts of the Illinois Basin where deeply buried marine limestones and dolomite with siliceous cherts formed with marine carbonaceous shale bedrock in the upper sections. To the southwest remnants of "Patch reefs” throughout the Silurian and Barrier reefs that formed around lagoons and in arcs near Terre Haute can be seen occasionally in outcrops. Late Devonian inland seas changed to gray and black limy muds from infusion of high amounts of algae and organic plant matter known as the "Black Shales" a source for oil and gas. Influx of late Devonian sediment coming from the Acadian Orogeny to the east lasted for 50 million years into the middle Mississippian (359-323 mya) and Pennsylvanian (322-299 mya) aka. the Carboniferous Period. Flat glacial till plains and agricultural land continues along I-70 in Illinois from the border at Terre Haute, Indiana to St. Louis, Missouri. Sediments coming from the eastern Acadian Orogeny formed huge equatorial deltas of clay, silt and sand that reached further west across the Illinois basin where marine communities of crinoids, bryozoans, 7
brachiopods, gastropods, various other bivalves and trace fossils predominated in a humid warm carbonate environment. Swamps and wetlands spread across exposed land areas for over 60 million years (36 my Mississippian, 25 my Pennsylvanian) where plant material from lycopods, conifers, seed ferns formed coal deposits while the very southwest remained a shallow sea. In the southwest Carboniferous bedrock exposures of shale, sandstone and limestone bedrock is mostly buried under till plains. The Carboniferous of Indiana continues into southern Illinois as sea level fluctuations and glaciers near the south pole migrated. This created alternating periods of marine inundation and dry land where Mississippian period limestones and marine fossils and early sharks occur. Later, Pennsylvanian bedrock exposes clay, silt and sand of large riverine deltas with swamps where coal was formed and the swamps contained a wide variety of plants and animals. We reached St. Louis after 268 miles at 4:40 PM and exited I-74 south to take I-255 around St. Louis, passed Cahokia, a famous huge Native American site in route to I-44 heading southwest for Springfield, Missouri. The Missouri River and the Illinois River flow into the Mississippi River in north St. Louis, the Meramac River from the west flows out of the Ozarks and enters the Mississippi from the southwest. The Kaskaskia River flows from the north out of Illinois to the south near where the Ohio River (combined with the Green, Cumberland and Tennessee rivers) all flow into the Mississippi River at Cairo, Illinois. The Mississippi River at St. Louis was the major outwash channel for all the glaciers and most of the continent before the glacial outwash buried bedrock 100-150 feet deep in the channel. Mississippian age cherty limestone, with some dolomite is known as the St. Louis limestone along with the glacial terraces forming 100-200 feet high cliffs along the west side of the Mississippi River. The west bank making up most of the city land was mostly covered with glacial alluvium, till, outwash terraces and loess, now, many of the terraces have been modified by land development. The Mississippi River channel on the east is a wide floodplain of braided streams and wetlands where large rivers from the north and east flow into the river draining much of the northeastern U.S. Heading southwest on I-44 from St. Louis towards Rolla, Missouri we start into the Ozark Plateau made up of Precambrian, Cambrian and Ordovician age bedrock. The Plateau bedrock consists of limestone, dolomite, shale, sandstone and chert higher in the east (part of an asymmetrical structural dome) where Precambrian granite and porphyries of the Saint Francois Mountains to the southeast are exposed from erosion and slopes lower in the west towards Oklahoma in the southwest. We traveled through the north part of the Courtois Hills of the Saint Francois Mountains with steep relief and valleys 400 - 800 feet deep. Some of the most rugged topography in the Ozark Plateau can be found here extending to the Central Plateau (aka. Salem Plateau) region. Lead, zinc and timber are the major economic products from this region. The Central Plateau, has a mean elevation of ca. 1,000 ft. asl, is mostly relatively low relief of 300 feet along the bluff lined Gasconade River flowing north to the Missouri River. The river flows through low and rolling Ordovician bedrock consisting of limestones with chert, dolomite and sandstone in a karst environment of springs, underground streams, sinkholes and caves. We pass through the city of Rolla in the center of the Central Plateau known for mining ore deposits of iron, pyrite, lead, barite, 8
and goethite left behind from eroded Pennsylvanian bedrock in sinks among the karst depressions. Geomorphologically, after Rolla, we passed through the northern part of the Ordovician plateau of the Gasconade River Valley as we entered into the Mississippian bedrock of the Springfield Plateau where there is a huge unconformity with the Silurian and Devonian missing, either eroded, or never deposited. We passed U. S. Army base Ft. Leonard Wood (Dalbey, played in an “All Army” volleyball tournament here in 1967) on our way to Springfield, Missouri . The Springfield Plateau is a gently westward sloping area of Mississippian age bedrock with more karst features and caves that continues into northeastern Oklahoma. In the Springfield, Missouri area the James River flows south into the northern Arkansas Chain O' Lakes region. In the southwest part of the Springfield Plateau the Spring River flows northwestward to westward over southeast Kansas and then south meeting up with Shoal Creek that flows west, south of Joplin, Missouri at Lowell, Kansas. West of Joplin the three state lines of Missouri, Kansas and Oklahoma come together southeast of Baxter Springs, Kansas. The streams flow south to Baxter Springs across the Oklahoma state line towards Wyandotte, Oklahoma where it meets the confluence of the Neosho River at the northern limit of the Grand Lake Of The Cherokees. All this land consists of grassland prairies and agricultural fields. After Springfield, Missouri we have traveled another 220 miles and it is after 9 PM when we get into Oklahoma and is now dark as night time was upon us. We kept driving west on I-44 on the Will Rogers Turnpike towards Tulsa, Oklahoma through the night. Clymer adds, the first beer run (not much of one, actually), was for Coors beer that wasn’t distributed east of the Mississippi back in those days, so it was coveted by many of us easterners. The first gas station we hit in eastern Oklahoma sold beer and was within the distribution area for Coors, so we bought a six pack just to sample the wares. “Don't drink them on the lot!,” the attendant warned. He could lose his beer sales license. Dalbey continues with his geological narrative, on the way to Springfield and then onto Joplin, Missouri we were traveling over Mississippian cherty karst limestone up to 1,800 ft. asl. The same formation continues into eight northeastern counties of Oklahoma and southeastern Kansas. Southern slopes consist of shortleaf pine, hardwood (Post oak) forests and what once was extensive prairies. The Springfield Plateau consists of the southern outcropping bedrock of lower early Kinderhookian/Osagean Series of marine shelves along Shoal Creek near Joplin. The marine bedrock is unconformably overlain by younger Mississippian marine shelf Meramecian Series of the Spring River catchment. Heading westward we enter the youngest Chesterian Series of the Mississippian and into the Cherokee Series of the Pennsylvanian in Oklahoma as we near Miami, Oklahoma and cross the Neosho River flowing south from Kansas. Further to the southwest, towards Tulsa on I-44 are the cyclical sandstones, siltstones, shales, clays and coal of the Desmoinesian of Late Pennsylvanian. The Cherokee Platform was located 10-15 degrees south of the equator during Middle Mississippian times developed on a carbonate platform that has been drilled for oil and gas in Oklahoma, Kansas and Missouri. The area is now considered the "Osage" plains and represents an old peneplain dissected by streams with 400 ft. of relief from 700 - 1,100 ft. asl. East of 9
Tulsa at Catoosa, a northern escarpment with Cross Timbers forest remnants stand along the Verdigris River, on the south is the Sandstone Hills with some steep walled canyons. At Tulsa (185 miles west of Springfield, Missouri it was 12:10 AM on Wednesday, 6 September) we remained on I-44 and kept driving, crossing the Arkansas River with steep embankments of lenticular sandstone, shale and limestone of the Cherokee Plateau. Past Tulsa, west of Bristow, Oklahoma ca. 40 miles we passed through the Virgilian Series of Upper Pennsylvanian bedrock on the periphery of the tectonically active Nemaha Trend that runs north into Kansas and Nebraska from Oklahoma City. At Witcher, Oklahoma we went south 30 miles on I-35 to Oklahoma City (total 114 miles) arriving there at 2:30 AM, and followed I-40 west towards New Mexico. I-40 parallels the North Canadian River through the city until we crossed the river on the west side of the city headed for El Reno in Canadian county. The Nemaha Trend structure occurs west of the Humboldt Fault Line that runs from the Oklahoma City area, north into Kansas and southern Nebraska. The Nemaha Trend represents a buried range of Precambrian/Phanerozoic mountains of a mid-continent rift system of ancestral (Laurentian ?) mountains that may represent an aulacogen that was active during the Middle Mississippian Period (340 mya) and continued active into the Pennsylvanian as thrust faulting occurred across the range. Broad areas were raising and lowering, receiving large amounts of sediment forming marine Pennsylvanian shelfs of sand, silt and clay up to 2,000 to 5,000 feet thick. After relatively stable shallow seas that resulted in limestone/chert deposits of the lower to Middle Mississippian, basins subsided in southern Oklahoma where sediments built up deep deposits while northern platforms in central and north central Mississippian bedrock eroded, creating an unconformity in the early Pennsylvanian. The Pennsylvanian was a time of orogenic uplift and basin subsidence in the south while broad areas of platforms were rising and lowering in the north. Sediments in the Ouachita, Arbuckle and Wichita basins were consolidating, uplifting, causing deformation from faulting and folding that led to forming major mountain ranges. Each range had a nearby adjacent deep basin (12,000+ feet), such as the Ouachitas in the southeast with the Arkoma Basin on the north bordered by the Ozark Plateau. The Arbuckle Range in the south central area had the Ardmore Basin on the northeast and Marietta Basin on the south. The Wichita Range had the Anadarko Basin (16,000 to 40,000 feet deep) on the north and west that also received sediments from an ancestral mountain range (Rockies) to the west and the Hollis Basin on the south. The Pennsylvanian bedrock contains more petroleum reservoirs than any other rocks in Oklahoma as these sediments contain abundant animal and plant fossil remains from 30 my of pulses of orogenic mountain building. Uplift across the southern orogenic belt (Arkansas to east Texas) exposed older fossiliferous and mineral bearing bedrock (Precambrian to Mississippian) causing erosion at various locations throughout various times during the Pennsylvanian. Each basin contains significant natural resources such as the Arkoma Basin in the east and south of Tulsa known for coal deposits from swamps during the Desmoinesian (315-307 mya). This was during the rise of amphibians, reptilians, and synapsids, all followed by an extinction event 305 mya known as the Carboniferous Rainforest Collapse. In the Virgilian (304-299 mya), the latest in the Pennsylvanian period the 10
Arbuckle Mountains reach their maximum height and have hydrocarbon deposits and the most diverse mineral deposits in Oklahoma. The Ardmore Basin has significant hydrocarbon reserves as does the Anadarko Basin in central and west Oklahoma. The Oklahoma area is still located near the equator and central part of the land mass Laurasia within the supercontinent of Pangea in the Virgilian (the last Pennsylvanian period) before a long Permian unconformity. The geomorphology of the east to west I-40 corridor goes through the relatively flat Central Plains short grassland prairie of Oklahoma north of the mountain ranges to the south discussed above. We are traveling in the largest geographic region of Oklahoma known as the Red Bed Plains that run north and south through Oklahoma consisting of flat plains, dunes, rolling hills, layered shale, stratified sandstone, and red mudstone. Not much surface geology to see along this stretch even if there was daylight. Route 66 (old “well known” TV program) converges with I-40 east of Weatherford, Oklahoma as we crossed the Canadian River. We entered the region of the Anadarko Platform at the shallow end of the huge subsurface Anadarko Basin that reaches into west Texas. After the Red Bed Plains, heading west we travel into the Gypsum Hills, a semiarid plain with mixed grassland prairie, gypsum outcrops, rolling hills, mesas, buttes, dunes, caves, and shallow canyons. In the subsurface, the west Anadarko Basin reaches as deep as 40,000 feet (ca. 8 miles) near the town of Erick in Beckham County, near the Texas border. The basin is bounded by the Wichita-Amarillo Uplift with numerous west to east trending faults on the south side of the basin, the Nemaha Trend (fault line) on the east, the Anadarko Platform to the north, and the earliest of the Rocky Mountain orogenies to the northwest. The basin is the largest and most significant natural gas resource basin in the U.S. with large petroleum (crude) reserves, helium, and iodine. Most of the mountain building processes were completed and located where they are today, however, ranges today have lowered from their original height after 300 my of erosion and burial by sediment like in the Wichitas. The land surface west of Oklahoma City is part of the Great Plains and continues into the panhandle of Texas as we head towards Amarillo, Texas. We crossed the Texas state line on I-40 at the town of Erick in Beckham County, Oklahoma and into Wheeler County, Texas to start a short drive across the Texas Panhandle to Amarillo, and then, west to Tucumcari, New Mexico. The Panhandle is made up of complex geologic events such as the Amarillo-Wichita Uplift, an east to west trending arch that I-40 follows toward Amarillo with the Wichita Uplift extension oriented north into Oklahoma and Kansas bordering the huge Hugoton natural gas field. West of the Anadarko Basin the bedrock changes to subsurface Permian bedrock of the earliest Wolfcampian (Red beds, 295-280 mya). These were followed by the Leonardian (280270 mya) Red beds, with anhydrite deposits, and another extinction event at 273 mya. During the following Guadalupian (271-258 mya), it was a time of the rise of therapsids that occurred during tropical climes that changed to colder and dry climes towards the end of the period causing another large extinction event from 265-259 mya. This was followed by the Ochoan (evaporates 258-250 mya), that contains the P/Tr (Permian/Triassic) boundary at 252 mya, a time of the largest biotic extinction this planet has experienced where an estimated 90+ percent of the flora and fauna of the planet vanished. This series mostly consists of bedded limestones, sandstones, shales 11
and peritidal dolomites. Sediments from the uplifts including the Bravo Dome on the southwest, and the Amarillo-Wichita Uplift on the southeast are deposited in the Dalhart Basin and Palo Duro Basin. Faulting and downwarping had ceased by the end of the Pennsylvanian and basin filling continued through the early Permian Wolfcampanian through most of the Panhandle but structural deformation continued northwest along the Cimarron Uplift. The Dalhart Basin is west of the uplift and the Palo Duro Basin is south of the faults where deep sediments from the uplift were deposited into the basins that were uplifted again exposing Palo Duro Canyon red bed strata deposition to erosion forming the second largest canyon in the U.S. 20 miles south of Amarillo. The surface of Palo Duro Canyon rims and other mesas, buttes, and crested surfaces are covered by the Caprock that formed ca. 2 mya. Stream erosion down cutting through the Permian Ochoan Series (280-250 mya) bedrock exposed the Quartermaster Formation "red beds" of shale, siltstone, sandstone and mudstone predominant in Palo Duro Canyon. The "red" and "yellow" hues in the canyon and mesas stratified bedrock comes from oxidation of iron and sulfide minerals such as hematite, goethite, limonite and sulfur minerals weathered from the sediments. Ash beds in the lower Quartermaster Formation of the Ochoan Series have been K/Ar dated to the P/Tr boundary 252 mya mass biotic extinction event discussed above. It was dark when we crossed the flat prairie to rolling plains from Oklahoma City into the Texas Panhandle. The Rolling Plains are now a short grass semi-arid prairie but was a high to medium grass (Buffalo grass, Blue Stem, Blue Grama, Sideoats Grama, etc.) prairie before European settlement. There are a few yellow-red beds outcropping in basins, mesas, cuestas and sand dunes in the short grassland also known as the Caprock as we get closer to Amarillo the topography gently elevates. The Caprock is a north to south escarpment of 50 to 100 feet high red to tan rock cliffs on the east, 200 miles long, relatively flat, gently east sloping plateau that rises as much as ca. 1,000 feet asl to the west. The Caprock occurs between the rolling North Central Plains of Texas and Oklahoma, and the High Plains of the Llano Estacado (from hereon, LE used for Llano Estacado) to the west, and the north bank of the Canadian River on the north. Towns along the meandering steep east edge of the escarpment originate from Mesquite on the south, north to Quitaque (Kit-ta-Kway) where Caprock State Park is located at the south end of the 120 mile long Palo Duro Canyon. The canyon was eroded by Prairie Dog Town Fork of the Red River, north to Goodnight 20 miles south of Amarillo and I-40. We arrived at Amarillo, Texas at 7:30 a.m. for a pit stop 320 miles west of Oklahoma City on 6 September 1972. As an aside, Dalbey draws attention to an interesting occurrence thirty-five miles north of Amarillo on Hwy. 136 near the town of Fritch. West of town is Lake Meredith and the Alibates Flint Quarries National Monument that is part of the Ogallala Formation. The quarries occur on top of mesas with over 700 surface mined pits used extensively by Native Americans as far back as 12,000 years ago. The flint, or agatized dolomite is multi-colored with red dominant mixed mostly with blue, gray, white and tan colors. It has been found over one thousand miles away and considered as a trade item for stone tool use. The Antelope Creek Culture (AD 1200-1450) that lived along the Canadian River used the flint extensively.
12
In Palo Duro canyon the Ogallala Formation (23-5 mya) at the top of the canyon surface unconformably overlies the Triassic Dockum Group. The Triassic consists of basal nonmarine Tecovas Formation shale, siltstone, sandstone and chert that formed in a low relief floodplain followed by a disconformity and the Trujillo Sandstone that form cliffs in the canyon. The basal sandstones are Permian (Quartermaster Formation) bedrock on the canyon floor followed by a long disconformity. The Quartermaster Formation consists of overlapping alluvial fans created from eroding western mountains in the uplifted interior seaway that became the High Plains. The derived sediments of sand, gravel and cobbles became solidified with CaCO3 (caliche) and silica forming a cemented “hardpan” (subsurface petrocalcic zone). Later, in the Pliocene/Pleistocene the Ogallala Formation was covered by fine wind blown dust sediments that formed the white Blanco Formation 5-3 mya in Blanco Canyon consisting of calcium carbonates derived from the Ogallala Formation. There are several of these west to east canyons throughout the High Plains and the east side of the LE. The LE slopes west to east with higher elevations to the west in New Mexico where stream drainages have formed and stream flows have created many canyons on the east face of the LE (See September 18th for more Ogallala Formation description). The "red beds" began as we went west of Amarillo on I-40 ascending the LE (translated “staked plains") at Adrian, Texas towards Tucumcari, New Mexico (hereon, referred to as NM). The entire LE geomorphological feature spans 150 miles west to east across the north scarp of the Canadian River corridor into Oklahoma. Then, south into Texas, and the scarp extends south from Adrian, Texas ca. 250 miles to Hobbs, NM. The LE extends further west to Roswell, NM, and northwest along the Pecos River corridor with the Mescalero Ridge escarpment forming the west edge of the LE and east bank of the Pecos Rriver. In the area south around Roswell, NM evaporites containing potassium and chloride white salts from an old marine seabed where rudists colonies and brachiopods have been recorded on the periphery of the Delaware Basin reflecting a warm shallow equatorial Permian sea. On the south, the LE transitions into the Edwards Plateau continuing south to the Guadalupe Mountains. The LE is made up of playas, canyons (breaks), flatlands, windblown dunes, Blancan formation white cap caliche "hardpan" flat surface, water, hot summers and cold winters. The Ogallala Formation makes up the sediments of the subsurface of this tableland capped by caliche as described previously, unconformably overlying Triassic and Permian bedrock. The current climate is arid to semi-arid with savannah, sparse short prairie grassland of many native prairie species such as Silver Bluestem, Buffalo Grass, but also includes non-native invasives such as KR Bluestem, Bermuda, Buffelgrass and Johnson Grass to name a few. Some of the most common plants are gauras, sage, astragali, sumacs, broomweed, snakeweed, to name a few. The arbor species including shrubby sumac vegetation in open parkland consists of pines, junipers, hackberries, walnut, mesquite and cottonwood trees spaced thinly over red colored (Fe oxidation) sandy soil. Winds and water have eroded less resistant bedrock leaving behind dunes, mesas, cuestas and buttes. As we traveled further west on I-40 through the red soil of the LE we pass many isolated mesas that resemble planed off hills with steep scarp-like sides capped by resistant Blancan Formation "hardpan." Mesas are smaller in area (ca. < 15 sq. 13
km.), while cuestas have one steep scarp side and a sloping backside over a much larger area than a mesa. Buttes are small weathered remnants, often of mesas with resistant caprock where steep sides of sedimentary bedrock of sandstone, shale, and mudstone form "pillars" as we see along the road in NM. Buttes are larger sedimentary structures unlike more isolated "hoodoos" (rock pilars) as also seen along the road. Most of the mesas we saw have a slope to the east away from the Rockies towards Oklahoma. The bedrock was Cretaceous that had been eroded away after uplift and erosion of the mountains to the west. West from San Jon, NM on the LE, closer to Tucumcari, we entered the Tucumcari basin, an ancestral Rocky Mountain structural depositional basin from the Pennsylvanian into the Permian. The present topography consists of high plains, rolling hills of the LE underlain by Triassic red beds (Dockum Group, Chinle Formation). Mesas formed as erosional remnants of Jurassic (mostly Morrison Formation), and Cretaceous (mostly Dakota Sandstone) caprock. The sediments around Tucumcari are Jurassic, mostly Morrison Formation consisting of siltstone, sandstone and shale/mudstone with thin limestone layers from continental terrestrial deposits that contain uranium ore and some dinosaur remains. The Jurassic sandstone Exeter Formation and mostly strata of the Morrison Formation overlie the Triassic separated by a disconformity followed by promontory caps of Cretaceous sandstones and shales. The subsurface geology is complex consisting of faults, uplifts, mountain ranges, Bravo Dome, deep elevator (long troughs) sub-basins next to uplift flanks, or adjoining shelf areas. The "red" color of the soil surface is from iron oxides such as goethite weathering to hematite. Forty miles into NM we came to the first mountain peak named Saddle Back Mesa rising above the 5,000 ft. asl LE south of Tucumcari. It became clear once we entered NM that we were traveling in mesa country. After Tucumcari, ca. 100 miles west of the Texas border we have finally reached the main interest of the field trip heading for the Colorado Plateau, albeit the foothills of the Colorado Plateau. At Santa Rosa, NM ca. 60 miles west of Tucumcari, on the banks of the Pecos River we are on the west edge of the LE. Santa Rosa is located at a huge six mile diameter limestone sink where porous caverns in subsurface limestone were eroded by underground water (Pleistocene or unknown age) that eventually caved in leaving rigid sandstone bluffs. Around the sink there are peripheral drapes of alluvium 250-400 feet thick that were later eroded after uplift in the area that created the prominent canyon. The Santa Rosa Formation of the Dockum Group consists of sandstones and mudstones of the mid to late Triassic Carnian age (237-227 mya) that is also fossiliferous with diversified flora and fauna including synapsids (mammal-like reptiles, Dicynodonts and Cynodonts) from the lacustrine Los Esteros Mudstones. The lower Dockum Group Santa Rosa Formation (Moenkopi of some authors in NM), exists as an aquifer in west Texas and does not crop out in the lower Dockum at Palo Duro Canyon. However, terrestrial Triassic formations around Santa Rosa are contiguous with Tecovas after Santa Rosa formations, followed by Trujillo Sandstones and later Redonda bedrock, not the Ogallala Formation as in Texas. The Triassic stratigraphic nomenclature has many authors with varied stratigraphic interpretations, but there is some consensus to indicate from central NM, to east of Amarillo, Texas the Triassic
14
along the I-40 corridor was one continuous land mass with varied biolithofacies ca. 240220 mya. An hour west of Santa Rosa, on I-40 we came to Clines Corner in the Basin and Range part of NM of the Rio Grande valley with upper Triassic Redonda bedrock. Fifteen minutes south is the Pedernal Hills with an 8,000 foot peak, part of the Pedernal Uplift bordering the Tucumcari Basin, Bravo Dome, and the slight Frio Uplift that separates it from the Palo Duro Basin to the east. South of the Pedernal Uplift is the Sacramento Uplift and mountain range with peaks almost 10,000 feet asl. To the north of Clines Corner is the Sangre de Cristo Mountains with Wheeler Peak at over 13,000 ft. asl. These two mountain ranges in part help form the Rocky mountain front range to the north. As we go west from Clines Corner to Albuquerque we pass through the closed flat basin of Estancia Valley with seasonal north-south playas from ca. 6,000 ft. asl to 9,000 ft. asl. bounded by the Manzano Mountains to the west, Pedernal Hills to the south (ca. 8, 000 ft. asl), further south Chupadera Mesa (ca. 7,000 ft.asl) and the Santa Fe High Plateau on the north. The late Paleozoic structural basin floor bedrock dips slightly east with slightly brackish groundwater. As we get closer to Albuquerque (from hereon, ABQ used for Albuquerque) we can now see Sandia Peak of the Sandia Mountains to the north and Manzano Mountains (Spanish for apple tree) to the south of I-40. Both ranges run north and south and are considered the Sandia-Manzano Mountains, separated by the Manzanitas Mountains and Tijeras Canyon in the center. As we approached ABQ it became clear we were in the land of volcanism as we advanced west on the eastern part of the Colorado Plateau. The Sandia Mountains are much younger than the Sangre de Cristo Mountains and not part of the Rocky Mountains. They occur a relatively short distance to the east and north consisting of old Proterozoic metamorphic rocks and late Paleozoic rocks. The Sandia Mountains were uplifted ca. 1 million years ago as part of the Rio Grande Rift forming the east boundary of the ABQ Basin. One explanation for these older rocks is that during the Mesozoic the late Paleozoic the continent was becoming emergent giving rise to continental conditions with swamps, bogs and alluvium as we saw to the east. Tectonics were occurring and as uplift occurred sediments from the uplift were deposited in nearby basins. Sediments were deposited in the closed San Luis Basin to the north of ABQ between the Sangre de Cristo Uplift and the Tertiary volcanics to the northwest, and the San Juan Basin to the west of ABQ. At the top of the Sandia Mountains (highest Sandia Crest 10,678 ft. asl) limestone strata of the ca. 300 mya Pennsylvanian outcrop occur. The pinkish hue to the mountains is provided by potassium feldspar in the granite as we observed huge blocks of the pinkish granite and green micaceous possibly metamorphic rocks that were probably Precambrian along the road. There was some folding of reddish beds at tops of features and many occurrences of normal and reverse faults. The granites were jointed and cross wedged with exfoliation observed on some granites with zeolites that could be spotted from the vehicle as we passed. Zeolites occur in metamorphic rocks as hydrous aluminum silicates, or alkali earth metals. They can occur in amygdales (vesicles in volcanic rock filled with secondary minerals, such a quartz, calcite, chlorite and various zeolites) or filled voids left from bubbles, or steam escaping from magma in volcanic rocks, and in
15
other late stage hydrothermal environments. They have close affinities to feldspathoids such as nepheline and other lower silica content minerals. For a perspective, from the top of the mountain one can see the Sangre de Cristo Mountains, Jemez Mountains, Mt. Chicoma (11,561 ft. asl) to the south, Mt. Taylor (11,305 ft. asl) of the San Mateo Mountains to the west, Magdalena Mountains (South Baldy peak 10,783 ft.asl) to the southwest, and the Manzano Mountains (Manzano peak 10,098 ft. asl) south of ABQ. Looking to the east towards Amarillo across the Estancia Valley we just came through, and further in the distance, we can barely make out some the mostly Triassic sediments discussed previously, and the massive eastward tilt of the LE as we traveled west. The Sandia and Manzano mountains form an east tilted fault block of the east edge of the ABQ half-graben basin of the Rio Grande Rift. The Albuquerque Basin at ca. 4,700 ft. asl is the oldest of the three major basins in the Rio Grande Rift Valley with sediments over 20,000 feet deep forming the Santa Fe Group from fifteen to one million years ago and is the aquifer for ABQ. There were volcanic eruptions in the west basin about seven miles west of where the city is located as late as 156,000 years ago. This occurred as part of the Pleistocene where basalts and andesites have been partially covered by wind blown sand sheets and dunes as part of the basin geomorphology. On the west of the basin Mesa Lucero provides an example of an earlier volcanic field 27.5 mya followed by other later volcanic events up to two million years ago. The Cordilleran Orogeny, a long mountain building process that began mainly in the Jurassic and late Cretaceous, included volcanics in the mid-Cenozoic later causing the San Andreas Basin and Range rifting in the late Cenozoic. The Laramide Orogeny from 80-35 mya at the end of the Mesozoic into the early Cenozoic was followed by the mid-Tertiary volcanics 40-25 mya, all contributed to the formation of the uplifted (1 km) Colorado Plateau 80-50 mya, that uplifted again 40-5 mya. At ABQ we finally reached the object of the field trip, the Colorado Plateau. We arrived at ABQ at 1:30 PM on 6 September (Wednesday) after traveling 281 miles from Amarillo, Texas. and 30 hours since the beginning of the trip on the 5th. We stopped at a KOA located on Coors Pike and witnessed a sensational sunset followed by rain most of the night, the first night we got to sleep on the ground. Clymer, comments that during the night, or very early morning of the September 6th, our four car caravan lost one of the members. Tail-end Charlie was unable to keep pace and the rest of the caravan made a wrong turn. The stray vehicle followed the prescribed route and instead of catching up managed to pass the other vehicles that were on the unexpected detour. So we had an opportunity to test the effectiveness of our, “the-next-post-office” rule. We drove past the post office and there were the lost souls leaning against the wall. In this case it was ABQ our first stop since leaving Cincinnati. Camp dinner in ABQ the first night, September 6th, was served up at a KOA. After the camp was secured, a food and drink run was initiated. For the 17 people, the run crew returned with several buckets of Kentucky Fried Chicken, two six packs of Coke, and
16
three cases of beer. I asked why they got so much beer and was told that's only four beers apiece. I believe two cases remained untouched that evening. Carter adds, once we arrived at ABQ, we were exhausted. It was a 30 hour brutal drive. I still hardly knew anyone except Phil, Mike Honnert, Tom Parker, and Steve Bernius who were also in Big Red. I have a memory that our campsite was on a slight hill with flat platforms cut into it. We watched the sunset and it was one of the most vivid ones I had ever seen. I don’t recall ever just slowly watching the sky transform across the color range, and in order, of an actual rainbow. The high clouds just magically changed colors until we were swallowed by darkness and the flickering lights of ABQ. From the KOA we could see the magnificent Sandia Peak rising to an elevation of 10,678 feet to the east of ABQ. The Manzano Mountains were visible to the southeast. Out west there’s so much sky with no trees blocking the view in most places. Cincinnati had too many trees blocking sunsets. I only was ever able to see a true sunset on my paper route years before watching the sun set behind the bluff across the Mill Creek Valley. I know I slept under the stars. I’m sure most of us did this every night. We had the department’s platoon-size canvas shelter but if the weather was clear we didn’t bother to erect it. We must have smelled like a sewer. But sleeping in the open allowed a spectacular view of the starry skies, with an occasional lagniappe of a glimpse of a shooting star. Dalbey continues, when we arrived in ABQ on the evening of the 6th we had to cross the Rio Grande River to the west side of town on I-40 and found a KOA for the night. When we crossed the river we crossed the Rio Grande Rift Valley, a 1,000 km (621 mi.) north to south trending alignment of faults that occur from central Colorado to Chihuahua, Mexico. The rift is one of five in the world (comparable to the East African Rift), that are not on a plate margin, but where the crust thins and pulls apart. The faulting in the rift consists of many east-west tilting half grabens, four major half grabens, where lava, volcanic ash and sediments from surrounding mountains built up. Then, the Colorado Plateau plate began moving away from the High Plains (LE) plate causing an east-west extension of the crust to thin bisecting the state of NM. The Earth's crust arched and widened, weakened, and spread apart in the south from magma rising below that began in the south 36 mya, later 26-29 mya in the ABQ area, and as late as 10-16 mya in the north where it is narrower from ABQ northward. Some sections of the rift dropped by over 20,000 ft. (8,000 m), filling later with over 15,000 ft. of sediments as the plateau rose 1,500 ft. from tectonic activity. The course of the Rio Grande River is controlled by the rift, and the current river flow represents a riverine system that was superimposed in the basin, that began flowing only 3-4 mya. At 8:00 A.M. Thursday, September 7th, we started out going west on Hwy. 66/I-40 out of ABQ traveling over Quaternary sediments deposited from the mountains around ABQ. A short distance west of ABQ we went over the Rio Puerco River, a tributary of the Rio Grande River. As we drove further west across what appeared to be the flat desert of the ABQ Basin, the largest of the four major rift basins is covered with Plio17
Pleistocene Sante Fe Group sediments 100-400 ft. deep. The Rio Grande River started downcutting the three million year old Sante Fe Group sediments about 1.2 mya ago before localized volcanic eruptions began. Within the first five to seven miles to the north is the ABQ volcanic fields that erupted 200-156,000 years ago forming Ceja Mesa along a five mile linear field consisting of six large cones, 10 smaller spatter cones, some individual spatter cones occurring along fissures. The Vulcan Cone is the highest of the spatter cones at 200 feet among the other five in the long chain of volcanoes with Black Volcano still active. Petroglyph National Monument is located in this volcanic field and displays 25,000 rock art engravings on tholeiitic basalt 3.5 miles north of I-40. After crossing the Rio Grande Rift Valley as we headed west we entered the Colorado Plateau (CP) Province made up of six intermontane plateaus within the contiguous Four Corners area of NM, AZ, UT and CO. Many theories have been proposed on how the CP formed, one considers plate tectonics where the Farallon plate was subducted under the North American plate as it moved east causing plates to rise. Another, hot mantle plumes under the plateau plates pushed upwards, and huge faults such as the Hurricane, Sevier, Paunsaugunt and a myriad of other north and south trending normal faults in the High Plateau Section created tensional forces in the Basin and Range Province causing westward movement. This is important because most of the geological focus of the field trip was on the Colorado Plateau (CP). Within the CP there are six physiographic sections and we traveled through five of the six. The east to southeast most of the CP is the (#1) Datil Section including El Malpais volcanic fields, Jemez Lineament south of Gallup, Zuni Mountains and more volcanism south. To the west, northwest of the Datil Section is the (#2) Navajo Section after Gallup, NM towards the Painted Desert and the Petrified Forest. The southwest to west part of the CP is the (#3) Grand Canyon Section mostly in AZ that includes Meteor Crater, Bandera Crater and the Grand Canyon. The (#4) High Plateau Section is north of the Grand Canyon Section in Utah with Bryce, Zion, and many other spectacular canyons and fault zones. To the east in central Utah and west Colorado is the (#5) Canyonlands Section of the CP that includes Capitol Reef, Arches, Canyonlands, and Black Canyon of the Gunnison. We really didn’t travel through the (#6) Uinta Basin Section of the CP to the north of the Canyonlands Section, we skirted the very south part of the section before entering the western Rocky Mountains Province in Colorado. The high mountain range we see as we look northwest from Mesita and Laguna, small towns on I-40 is the San Mateo Mountains (aka. earlier as the Cebolleta - "tender onion," Spanish translation) in the Navajo Section of the CP. This is where the composite stratovolcano Mt. Taylor (ca. 11,300 ft. asl) erupted producing a large trachybasalt lava field to the northeast partly later covered by the Cibola National Forest. The volcanic field overlies Cretaceous sedimentary rocks and is part of the Jemez Lineament (JL), a 500 mile long alignment that varies from 10 to ca. 100 miles wide at 10 volcanic centers that run from southeast to central Arizona in the Datil Plateau Section, northeast through NM to southeast Colorado. The eruptions along the JL have gone on since 1.7 bya but have been more active since the Miocene. The JL has produced about every landform and structure known to be associated with volcanism. Mt. Taylor was active 4.3 to 1.5 mya and has been mined for uranium and vanadium for 40+ years. 18
To the west, the San Juan Basin is a structural depression with 3,000 feet of variation in elevation that contains the well known Native American Pueblo Culture site Chaco Canyon, the towns of Farmington and Santa Fe, and the continental divide on the west part of the basin. The land mass plate that became the basin has been in existence since the Precambrian in some form or another as it moved from the southern hemisphere, to the equator, and later to the northern hemisphere. The basin has a long geologic record providing a source for oil, gas, and methane rich coal beds. During the Jurassic, a collision of the terrestrial Farallon Plate with the terrestrial North American Plate caused subduction of the western margin. This caused subduction of the Farallon Plate under the North American Plate causing a depression in the interior that created shallow marine environments that filled the Western Interior Seaway by the early Cretaceous. Continued subduction of the Farallon Plate caused uplift of the Rocky Mountains and the Laramide Orogeny. This resulted in the extension of the Rio Grande Rift and volcanism elevating the plate eventually creating the San Juan River drainage east to west across the north part of the basin to the Colorado River at Lake Powell. As we traveled west on I-40 we made three stops before Grants, NM traveling through Triassic beds skirting around to the north side of the ca. 7,000 ft. asl Flower Mountain as we headed into small towns surrounded by Jurassic beds west of Mesita at Stop 1 and Laguna at Stop 2. A couple of miles down the road we observed the buff colored Todilto Limestone at the outcrop base followed by red beds of the Morrison Formation consisting of the Summerville and Bluff formation sandstones capped by Zuni Sandstone. From here, we could see buttes, mesas and cuestas with slumping debris covering the lower beds. The arid climate combined with the lack of vegetation makes the erosion processes occur rapidly. The whole area is streaked with washes that have flooded and eroded the surface for millennia. This process has gone on for a long time as loose sediments have been eroded by wind and water causing mesa formation as a result of the most resistant beds remaining. The Mesita and Laguna area falls at the east end of the Grants Mining District, an area of the largest open pit uranium and vanadium mine (Jackpile-Paguate mine, 10 miles north) in the U.S. where over 5,000 mining claims have been made in the area. The main source rock for the uranium is the Jurassic Morrison Formation (157 to 150 mya) sandstones that occur along the southern boundary of the San Juan Basin that runs along the north side of I-40 north into southern Colorado. It is thought that the origin of the uranium is cosmogenic coming from supernovae explosions in space multitudinous times since 4 bya. Or, perhaps neutron stars colliding producing huge amounts of heavy elements such as uranium in the solar system, or both, worked into the lithosphere released through magmas as continents moved, providing a simple scenario for a complex process. In the distance we can see the Zuni Mountains to the southwest of Mesita and Laguna that trend northwest with I-40 running on the north side towards Grants and northwest to Gallup NM. As we go west from Stop 1 near Mesita, and on towards Stop 2 at Laguna along I-40, we collected some of the Palaeozoic volcanic rock along the road as well as chert and jasper. I-40 runs along the south boundary of the San Juan Basin and is surrounded by Permian, Triassic and Jurassic strata. The process described above may be exemplified by the erosion of the lithosphere in that area. Precambrian granites containing uranium have been eroded for eons, as the rock becomes soluble with 19
groundwater uranium is leached out of the bedrock, where it is estimated that 20,000 feet of Cretaceous and other sedimentary rocks have been eroded away from the highest part of the range but appear to be deposited in the west and northeast in the San Juan Basin. The uranium derived from the uplift of the Precambrian granites and metamorphic rocks that occurred during the Pennsylvanian period were eroded, later uplifted to form the ancestral Rocky Mountains by ca. 280 mya. Several millions of years later the mountains were uplifted again during the Laramide Orogeny 80-40 mya. Since then, the weathered volcanic and eroded Zuni Mountains (peaks > 9,200 ft. asl) to the south of I-40, and parts of the mineral district, have been covered throughout other parts by the patchy Cibola National Forest. These areas are home to three Native American tribes living on tribal reservations: Acoma pueblo, Zuni reservation, Navajo reservation, and Laguna pueblo (Keresan speakers) made up of Puebloan tribal remnant groups. The short 60 mile long San Jose River flows east from the Zuni mountains with headwaters at the Continental Divide, then, flows roughly parallel to I-40 where it meets the Puerco River west of ABQ before flowing into the Rio Grande River at ABQ. After Stop 2, we observed aeolian fossil sand dunes and lava layers in the sediments. Cebollita Peak on the mesa at ca. 8,800 ft. asl could be seen to the south as we crossed the northern outlier of Cebollita Mesa. Faulting occurred as it looked like steps in the Jurassic strata. Cebollita Mountains were covered with lava flows, some Tertiary in age and outcropped in columnar jointing. When the lava cooled it shrank causing tensile jointing perpendicular to the flow as the lava splits into long vertical prisms or columns. At Stop 3, we observed more basaltic volcanism from fissure flows as I-40 cuts through the McCarty Lava Flow where we observed extremely rough 'A'a lava flows and broken crusts of pahoehoe lava flow near the town of McCarty. The McCarty Lava Flow we observed along the north side of I-40 and along Hwy. 53 as we turned south are part of the Zuni-Bandera Volcanic Field, which covers over 900 square miles. The youngest flows in the field happened 3,000 years ago. Olivine crystals very small in size were observed in the basalt. All of the lava flows in the area were 'A'a named from lava flows in Hawaii composed of very rough vesicle flows. The vesicles reveal how the lava cools as gasses escaping would rise and some were trapped making the basalt porous. Some pahoehoe lava flows were also observed in this area as they appear ropy, smooth or hummocky, as they advance in a series of small lobes. On top of a mesa off the road (I40) we observed the 3,000 year old McCarty's ash flow. It consisted of volcanic tuffs, rhyolite, and granitic rock, part of the massive Zuni-Bandera Volcanic Field. The ash flow represented a liquified flow part of the Mt. Taylor Volcanic Field. Further south of Grants, NM on Hwy. 53 as we circumvented Mt. Sedgwick (> 9,500 ft. asl) on the west, one of the highest peaks in the Zuni Mountains we were still crossing Cebolitta Mesa to the east. We passed through part of the Malpais (Spanish for “badlands”) Volcanic Field and north of the National Monument as Hwy. 53 curves west through more of the Zuni-Bandera Volcanic Field and part of the JL discussed previously, On Hwy. 53 we passed near a relatively recent volcanic flow along the road 20
passing south of the more than 10,000 ft. asl Gallo Peak heading for Bandera Volcanic Crater, Ice Cave and El Morro. Bandera Volcano represents a symmetrical breached cinder cone that formed during eruption where the basalt flows were visible for miles in the distance. On our way to Bandera Crater we are passing through a large part of the Cibola National Forest with pines growing in sediments of weathered granite. At Bandera Crater the primary cinder cone is 500 feet tall, > 3,000 feet wide, and 800 feet deep. Bandera Crater is also noted for its spectacular ice caves. The caves are formed as part of a series of tubes that are now mostly collapsed, but in the recesses that remain ice forms and in most cases persists throughout the entire year. There is a southwestern side breach that allows access to the central part of the volcano. We walked several various trails, the first trail we walked over 'A'a lava that was very rough
Where’s Waldo? Lizard sheltering in weathered basalt along I-40. Photo by Tim Carter.
Basalt flow along I-40 near Grants, N.M. Photo by Tim Carter. 21
Vesicular basalt in flow adjacent to I-40 near Grants, N.M. Photo by Tim Carter.
Bandera Crater viewed from the wall breach. Photo by Tim Carter. 22
and viscous at the bottom of the cone. There are many caves, part of the lava tube system that allowed basalt to flow away from the crater. An ice cave (tourist attraction) occurred in the midst of this lava flow where a cavity in the lava filled with trapped groundwater creating an eight foot blue-green ice wall that never melts. The cave temperature ranges from -1 to 50 degrees Fahrenheit (F) at the warmest, but averages yearly ca. 31 degrees F. The lava occurs in spatter formations as if when cooled it just froze in place. The brochures supplied by the Bandera private owners stated that the ice formed by cold air infiltrating the lava tubes during the winter months, but Dr. Larsen suggested that entrapped volatiles seeping from the basalts caused evaporative cooling and were likely responsible for the ice formation and preservation. The lava flow is very recent and Bandera Crater is one of the best examples of a cinder cone volcano in the United States. The trees around the volcano are contorted as we observed a ponderosa pine log twisted like a wash cloth by the lava. There are cavities in the lava such as Ice Cave and many others forming tubes and "hornitos' that were created by the lava rising vertically and bursting through a tube. After walking through the cave and over the lava flows we ascended the outer cinder cone to the north rim. The ejecta material we came upon was viscous and loose volcanic ash, lapilli of different shapes and sizes, including large (softball size) volcanic
Entrance to ice cave at Bandera Crater.
23
Interior of one of Bandera Crater’s ice caves. Photo by Phil Clymer. bombs. The prevailing winds affect the volcanic emissions at the time of eruption, the finer particles are carried the furthest out from the center while the larger fusiforms and bombs. The prevailing winds affect the volcanic emissions at the time of eruption, the finer particles are carried the furthest out from the center while the larger fusiforms and bombs are closer. The lava emitted was alkaline olivine basalt, along with silica mostly as the matrix with olivine included quartz and feldspathoid phenocrysts. The quartz might indicate some of the sediment existing before the eruption that somehow fell into the magma and was metamorphosed and ejected. Lapilli and fusiform bombs represent liquefied ejecta that solidify in the atmosphere. Lapilli are longer than wide, angular, small elongated cinders usually less than 1.5 inches in cylindrical, blob, or tearshaped forms that develop different colors due to the presence of mineral oxides. Bombs are larger, more rounded, often hollow, fusiforms are spindle shaped and larger than lapilli, but some were angular and all have a very rough surface. We collected lapilli and bombs on the crater rim but did not go down into the crater as the cone slope cinders were too loose and unsafe. Outside the volcano cone we collected fusiform bombs, lapilli, and tephra with sandstone inside, or other minerals, or crystals trapped in the ejecta. Some of the tephra (volcanic ejecta) samples were given to Dr. Larsen as he is interested in pyroclastic material that might be encased in the tephra ejecta as xenoliths inside the ejected lapilli, or bombs. When analyzed the xenoliths might be good for telling him about material in the mantle. Despite there being a sign warning against entering the crater proper, one of the more adventurous, or foolhardy members of our group scurried across the basalt skree in the blazing sun and worked his way to the bottom.
24
Helen Young atop a fumarole at Bandera Crater. Clymer adds, the trip was not just for geology, Dr. Larsen included cultural stops as well. One such stop was El Morro National Monument and Inscription Rock is where ancient Puebloans established a pueblo settlement on the mesa overlooking a natural spring. The mesa was formed from loosely consolidated Jurassic age Zuni Sandstone, and capped by Cretaceous age Dakota Sandstone. Built in the late 1200s it was occupied for nearly 200 years. The Puebloan people created many petroglyph engravings around a spring at the base of sheer sandstone cliff walls. Spanish visitors encountered the site in the early 1600s and continued the tradition of wall inscriptions. Following the Spanish, both locals and tourists added their marks until it was outlawed in 1907 when it was designated a national landmark. Dalbey adds, after Bandera Crater we headed west on Hwy. 53 and went to El Morro National Monument located on top of Jurassic yellow tan Zuni Sandstone (formed from a huge sand dune field) canyon capped by reddish to gray Cretaceous Dakota Sandstone. The promontory side of a cuesta that was occupied by ancestral Puebloan cultures from AD 1250 to 1325 lived in a 355 room pueblo housing ca. 600 people with a perennial spring at the bottom of the outcrop. Cultural material related to the Spanish entrada by Vasquez de Coronado ca. 1540-1542 looking for "Golden Cities" have been found at El Morro marking the earliest European occupation in the southwest and the nation's second declared National Monument after Devil's Tower in Wyoming. After El Morro we went west on Hwy. 53 a short distance as we crossed the Continental Divide and turned north on Hwy. 602 towards Gallup, NM at the junction of highways 25
53, and 36. The Zuni Formation bedrock is part of the San Rafael Group that makes up a large part of the plateau in northwestern NM that extends into Arizona northwest to the Grand Canyon. All of the time that we have been traveling west on mostly Interstates we have passed through 355 million years of geologic time from the Late Ordovician ca. 450 mya in western Ohio to the Late Jurassic ca. 145 mya in west New Mexico arriving in the Zuni Mountains south of Gallup, New Mexico. In the Gallup area outcrops of the late Cretaceous Gallup Sandstone occur unconformably over Jurassic age Morrison Formation within the Gallup-Zuni Basin. We finally stopped Thursday evening at Gallup and stayed the night at a KOA along I-40. After Gallup, NM we entered the Navajo Section of the Colorado Plateau. (As an aside, south of the junction of highways 36, 53, 602 and heading south on Hwy. 36 through the Zuni Reservation to the small town of Fence Lake, then south on Hwy 601 to Hwy. 60, then, west on Hwy. 60 at Quemado to Red Hill. This route leads into the large Red Hill-Quemado Volcanic Field that looks like it’s right out of a ‘martian’ landscape formed by monogenetic scoria on the JL containing over 40 scoria cones, silicic domes, salt deposits and lakes, numerous vents, maar lakes [shallow vents], some formed in the Pleistocene and Holocene as late as ca. 11,000 kya. Along the way there are 60 feet high deposits of volcanic conglomerate exposed at the base of outcrops. This was capped by an unconformity and ca. 250 feet of late Cretaceous Zuni Sandstone that cropped out through the Zuni Reservation, crossed Hwy. 53 toward Hwy. 602 into Gallup, NM). The next morning the 8th of September we left Gallup, NM planning to drive west on I40 that follows the southwestern edge of the San Juan Basin towards the Petrified Forest and the Painted Desert, stopping for the night in Winslow, AZ. Around Gallup, we observed volcanic remnants of the Navajo Monogenetic Volcanic Field in the distance. The volcanics erupted ca. 25 +/- 1 mya and can be seen in a north to northwest trend line of the East Defiance Monocline along the NM state line north to the famous Ship Rock Volcanic Neck remnant. This is also where the Mesaverde Hogback Monocline trends northeast into Colorado. To the west roughly paralleling Hwy. 191 the Defiance Uplift Monocline trends north and south to Chinle, AZ, perpendicular to Canyon de Chelly (pronounced de-shay). Other monoclines extend north to the Chuska Mountains, the Carrizo Mountains and west to Kayenta, AZ. All through the Defiance Plateau there are volcanic fields that contain ultramafic, ultrapotassic, igneous dark colored rocks in small volume deposits known as lamprophyres. These are associated with deep, possibly asthenosphere, or mantle intrusive igneous sources with mineral names such as minette, vogesite, kimberlite (diamond source), found around volcanic pipes, diatremes, and dikes from deep continental crust sources. Minette is one type of dark colored rock that is found associated with the Navajo Volcanic Field intrusives nearby, about five miles south of Gallup composed of alkali feldspars, biotite, phlogopite, diopside (pyroxene), and olivine occur in large phenocryst crystals.
26
Newspaper Rock in Painted Desert. Photo by Tim Dalbey. On our way west on I-40 from Gallup, NM heading towards Holbrook, AZ we entered the immense Painted Desert that spreads from I-40 northward to the east end of the Grand Canyon (7,500 sq. mi.) through the Navajo Plateau (NP). It also includes the canyons of the Little Colorado River that drains the Defiance Plateau northwestward and also includes the Petrified Forest (230 sq. mi.) on the southern end of the Painted Desert at the southern edge of the NP. The Defiance Plateau is a small domed uplifted block in the northeast quarter of NM with elevations ranging from 6,000 to 7,000 ft. asl. Riding along looking at stratified layers of bedrock you would never know that there was at least a 17 million year hiatus after the Permian of no deposition or erosion of the lower Triassic. This was the result of erosion and subduction along continental margins of Pangea. After the long hiatus the earliest sediments were deposited in an arid riverine coastal plain foreland basin consisting of fluvial, lacustrine and palustrine conditions in an aeolian terrestrial environment that made up the early middle Triassic Moenkopi grayish red beds. Some fauna made it through the extinction event such as Dicynodont Therapsids (such as Lystrosaurus sp.), Proterosuchids (Proterosuchus sp.), and Synapsids (proto-mammals). But the Archosauriformes that were in the late Permian that made it through to the Triassic multiplied as it was the time of Archosauriformes radiation that includes numerous crocodyliformes, pterosaurs, dinosauria and birds. The first dinosaurs occurred in the early Triassic from 243 to 233 mya with Coelophysis sp. dating to 230 mya in northern NM. Archosaurs (reptilian forms) have been recovered from the very colorful Dockum Group in west Texas, the Santa Rosa Formation (also Dockum) in eastern NM, and westward to the Chinle Formation through to Flagstaff, AZ a distance of almost 700 miles of Triassic bedrock formations. Ever since west Texas, as we traveled westward, we have seen persistent discontinuous middle to upper Triassic stratified bedrock formations. However, these sediments are not the first after the large Permian/Triassic (P/T) extinction event that 27
occurred 252 mya where an estimated 90 (+/- 5) percent of the fauna and flora on earth ceased to exist. After that event, inland continental conditions during the early Triassic were generally hot and arid even into polar regions where large scale erosion occurred in the early Triassic Moenkopi Formation red and gray beds. Early Triassic oceans were in crisis due to anoxia, influx of alkaline volcanic sediments, atmospheric levels of O2 decreased while CO2 increased in a depleted O2 atmosphere including oceanic circulation changes. Life after the extinction event took possibly 30 million years to recover, by then, the supercontinent Pangea was starting to rift into two large land masses. Gondwana to the south and Laurasia to the north with the large Laurentian craton (partly made up of the billion+ year old Canadian Shield) landmass towards the center of Laurasia. The area that was to become NM and AZ was on the equatorial southwestern margin adjacent to offshore rifted accretionary land masses and a long north to south linear chain of offshore volcanism. Sediments of coastal riverine environments were created that were favorable for flora and fauna to survive and also supported the flora that made it through the extinction. Through the boundary, climate may have changed rapidly due to the eco-crisis causing reduced precipitation, increased temperatures, as gymnosperms were replaced by lycopods (mosses, quillworts, spike mosses), Isoetales, horsetails, ferns, and larger lycophyte tree like plants such as prevalent Lepidodendron sp. These environments of various continental terrestrial deposits along with the post P/T extinction relict flora/fauna represent survival in a southeast to northwest flowing fluvial system. The system occurred in an equatorial Laurasia craton back-arc floodplain with volcanism to the west and southwest of what is now the Colorado Plateau in the Four Corners area. These environments supported larger vegetation such as cycads, gymnosperms (cone and seed bearing plants [no fruit], common species was Glossopteris sp.), conifers, gingko and other seed/cone bearing plants. Dalbey adds a side note: an alternate route we could have taken would have been a four hour side trip that morning after Gallup traveling 50 miles west on I-40 to Chambers, AZ. Then turned north on Hwy. 191, well into the Navajo Reservation for another 80 miles for the 1.15 hour ride to Chinle, AZ. But instead we went onto the Petrified Forest where we spent most of the day. If we had gone the Hwy. 191 route to Chinle we would have taken Rte. 7 east along the South Rim road of the spectacular Canyon de Chelly in the heart of the Defiance Plateau. What makes the E to W oriented canyons known as Canyon del Muerto on the north, Monument Canyon (middle), Canyon de Chelly on the south geologically so unique is the Defiance Plateau that represents an island of uplifted Permian strata tilted west in the middle of Mesozoic sedimentary strata isolated from other Permian strata that does not extend laterally. The uplift took place ca. 63 mya and again 3 mya. The strata making up the canyons in the plateau overlie Precambrian bedrock and consist of 1,000 feet of stratified mostly vivid bright vertical maroon red, red to red orange, orange to tan walls of the De Chelly Sandstone. The sandstone occurs between detrital early Permian Supai Formation sediments at the bottom and an unconformity (P/TR boundary) on top of the De Chelly Sandstone that precedes the Shinarump Member that caps the later Chinle Formation at the end of the Triassic. The basal earliest Triassic Moenkopi Formation does not occur in Canyon de Chelly caused by an erosional unconformity mentioned previously, but does occur in Beautiful Valley north of Chinle. The White House Member makes up 28
ca. 600 ft. of the sheer vertical 850 foot De Chelly Sandstone walls that consist of large aeolian tangential cross-stratified dunes (10-50 feet tall) that was once part of a large erg (cf. Sahara Desert) formed by proposed mega-monsoonal winds/rains from the south blowing northward. Calcium carbonate in the dunes eroded away leaving elevated pockets in the dunes where later Anasazi Native Americans built their cliff dwellings at well known places such as Antelope House, White House and Mummy Cave, to name a few. Ancestral Native Americans that lived in the canyons include: Archaic hunter-gatherers for longer than 2,300 years followed by the people known as Basketmakers (200 BP to AD 750) that lived in the canyon for 950 years who were horticulturist with cotton, raised turkeys, weavers, ceramicist and rock artists. They were followed by the Anasazi/Pueblo (AD 750-1300) people that built cliff dwellings, farming hamlets, ceramic specialist, traders, and considered the canyon a social and ceremonial spiritual landscape. Then, the Hopi (AD 1300-1600) who followed living a Pueblo life style that ended because of drought, conflict, disease, as they migrated south along the Little Colorado River establishing villages with seasonal farming, migrating to canyons and pilgrimages until the Navajo entered the canyon ca. 400 years ago (ca. AD 1600-1863). They raised domesticate sheep and goats, corn and peaches, all coming to an end with warfare with other Navajo, Spanish, Utes and U.S military campaigns. The canyons are still considered the Navajo homeland and have enlarged to the Four Corners of AZ, UT, CO, NM. Ever since ABQ we entered the realm of varying uplifted geologic blocks, plateaus, basins and volcanics of the complex Colorado Plateau. From the younger San Rafael Group south of the San Juan Basin along I-40, as we travel west, we travel back in time to the late Triassic Chinle Formation, then through the formations of the earliest middle Jurassic Glen Canyon Group that is made up of well known geological formations. The earliest Jurassic Formation in the group is missing due to a huge unconformity and extinction at the end of Triassic Chinle Formation also a time of major volcanism at the end of the Triassic. The second extinction event at the end of the Triassic 50 my later partly caused by wide spread volcanic eruptions especially on the east side of Laurentia where plate sutures between North America-Africa-Eurasia-South America within the central part of the of supercontinent Pangea all together created the Central Atlantic Magmatic Province (CAMP). After this time 201 mya the proliferation off the dinosaurs occurred as land masses spread. The Glen Canyon Group represents Pangean equatorial continental aeolian deposits in a foreland basin that received sediments weathered from the Sevier Mountains source area (Nevada, Utah to the west and northwest). These alternate with other formations and sediments that reflect river, lake, lacustrine, floodplain environments and back to aeolian formations from arid environments. The group starts with the basal earliest middle Jurassic Wingate Formation (terrestrial, aeolian, facies) that lies unconformably over late Triassic Chinle Formation. The Wingate Formation strata consist of massive orange to red (up to 400 ft.) oxidized aeolian wind blown relict cross-bedded sand dunes and laminar bedding of deserts and sandstones that outcrop as cliff faces 15-20 miles east of Gallup. The Wingate may have begun in the latest Triassic but earlier deposits have been eroded. Prevailing winds were from the south to southeast with 29
dunes estimated at 100-150 feet high. The Wingate Formation extends to the north, it started possibly as early as 210 mya in the late Triassic but contains a huge marine extinction event that occurred ca. 201 mya at the end of the Triassic. The Wingate Formation (ca. 210-200 mya) is followed stratigraphically, and laterally to the west by the later Moenave Formation (terrestrial facies made up of rivers, lakes and floodplains), that occur on uplifted and eroded Chinle surfaces. The Wingate and Moenave could be viewed as time equivalent contiguous lateral environments that contain an unconformity of ca. 10 million years. Later sediments were deposited in a northeast to southwest trending foreland basin trough. These earlier Glen Canyon group of Pangean continental terrestrial formations in NM/AZ occurred while a marine extinction and hiatus event (ca. 76 percent of marine fauna extirpated) was in progress. Pangea had begun to break up earlier, with Laurasia (including Laurentia - aka. North America craton) drifting north and Gondwana south. Volcanism occurred along an extensive western margin oceanic ridge, while more volcanism was established in the central Laurasian continent caused by the Laurentia Central Atlantic Magmatic Province (CAMP, mentioned previously). The global climate was changing, more humid and rain equatorially, overall warmer, polar caps minimal, ocean acidifying from volcanism. An anoxic ocean occurred during and at the end of the late Triassic Chinle Formation during the deposition of the Wingate/Moenave formations. The hiatus opened an ecological niche where dinosaurs evolved and the Sundance sea made several transgressions/regressions into the area before finally separating the middle Jurassic from the late Jurassic. Later, the Kayenta Formation (ca. 188-183 mya) follows, consisting of more continental Laurasian interbedded arid red to brown fluvial mudstones, siltstones, sandstones becoming more extensive to the north. The formation is up to 400 feet thick of maroon, dark red, red to lavender beds among more massive cross-bedded tan, buff pinkish red with some limestone formed in the same basin where it intergrades with facies of the Moenave Formation. The last late middle Jurassic formation is the massive Navajo Sandstone Formation (ca. 190 mya) that reflects an arid environment of wind swept surfaces creating large meter size migrating cross-bedded dunes and monsoonal rains during cooler periods. On Pangea, a massive area of the western terrestrial continent formed an erg, or a sand sea (comparable to the Sahara desert), that is estimated to be the largest on earth, also where extensive erosion occurred before the deposition of the San Rafael late Jurassic deposition. The formation intergrades with the earlier Kayenta Formation. Altogether, the Glen Canyon Group forms stratified outcrops in various areas 600 to over 3,300 feet high, consisting of bluffs, cliffs, mesas, cuestas, domes and large cross-bedded sandstones often consisting of alternating laminated white, tan, to light pink in color. The colors are from iron oxides in the sediments and the red color caused by water dissolution percolating through the sediments over time. The later Jurassic formations of the Colorado Plateau vary from basin to basin and are not consistent throughout due to faulting, uplifted block movements, erosion and several unconformities (n=5). In the northwest area of NM near Gallup the San Rafael Group in the San Juan Basin consists of five major strata and four unconformities. In the area of 30
northwest NM the early middle Jurassic begins with an unconformity followed by the massive Entrada Formation of red silty-sandstones and mudstones in some areas overlying the late Triassic Chinle Formation. The Entrada Formation is followed by the Todilto Formation that consists of brief periods of coastal lagoonal muds turning into shaly strata from the Sundance Sea, interspersed by influxes of freshwater runoff, arid periods of carbonate deposits capped by evaporites. The aeolian Bluff Formation is preceded by the late Jurassic Summerville Formation consisting of red mudstones with thin interbedded red and green sandstones, sauropod tracks, influenced by intervals of the Sundance Sea and freshwater sources. The Zuni Sandstone (fluvial, lacustrine to aeolian deposits in the Zuni Mountains) overlies the Bluff Formation (massive aeolian wind-blown sandstones). The late Jurassic was ending with the final transgression of the Sundance Sea. The Sundance Sea was an epeiric sea that extended southward from a northern sea that transgressed and regressed several times over long periods of time separated by erosion hiatuses during the mid to late Jurassic. Later, highlands to the west uplifted depositing terrestrial sediments over marine Sundance Formation sediments 157-168 mya hundreds of meters thick before forming the fossil rich Late Jurassic Morrison Formation. The Late Jurassic is capped by the Morrison Formation dating to 157-146 mya. Highlands to the west uplifted and eroded depositing terrestrial sediments over marine Sundance Formation sediments 157-168 mya amounting to hundreds of meters thick forming the fossil rich Late Jurassic Morrison Formation. The sediments covered a vast area where lateral shifts, faults, orogenies in various terrestrial environments causing differential exposures, but generally arid to the south (NM, AZ) and swampy to the north (NV, MT). These environments supported fossil tetrapods and dinosaurs that were deposited in 750 feet of fluvial mudstones, siltstones, sandstones and limestone. Therefore, as we traveled west from the Zuni Mountains near Gallup, NM and headed for Chambers AZ as discussed in the "side note” previously, we mostly go back in time. However, from these early observations of the formations we got a glimpse of NM that provided us with a preview of some of the over 3,000 feet of geological strata sections of the Late Triassic, Middle Jurassic Glen Canyon Group, and the Middle to Late Jurassic San Rafael Group to come when we travel north towards the Grand Canyon, Utah and beyond. Meanwhile, that morning as we drove west on I-40 ca. 85 miles out of the view of the colorful cliffs and mountains of the Jurassic Glen Canyon Group and the San Rafael Group we traveled back in time, after unfortunately, bypassing Hwy. 190 at Chambers, AZ to go north to Chinle and Canyon de Chelly. We entered back into the Triassic period and the expansive 7,500 sq. mi. Painted Desert at elevations ca.6,200 ft. asl. It consists of some of the most colorful landscapes anywhere in the world. Today, wind, rain and streams are eroding more of the Chinle Formation sediments at a rate of 6-10 mm a year revealing more and more petrified wood in the Chinle. The early Triassic Moenkopi Formation made up of coastal plain marine and fresh deposits 300-600 feet thick has been eroded. The Painted Desert consists mostly of the Chinle Formation with a basal thin conglomerate Shinarump Member unconformably over the Moenkopi Formation. The Chinle Formation consists of five members: the Lower Petrified Forest shales and sandstones, followed by the Sonsela Sandstone that 31
contains most of the petrified wood in the Petrified Forest, however this member is missing due to erosion in some areas. The Upper Petrified Forest Member consists of shales and sandstones with volcanic activity and ash falls in a western sea. Owl Rock is the last member that includes gypsiferous clays deposited in lagoons with more volcanic activity and ash falls in a western sea. Throughout the Chinle, deposition of sediments and uprooted vegetation during flooding buried organics quickly that preserved and prevented disaggregation of trees while groundwater permineralized the wood in the trees with silica while inundated. Deposition of several thousand feet of Jurassic and Cretaceous sediments were later eroded away. Tertiary uplift, warping, Laramide Orogeny, combined with the Defiance Uplift caused more erosion of the Triassic, Jurassic and Cretaceous sediments as new mountains off the coast cut off the Panthalassic ocean (later Pacific ocean) moisture from the prevailing southwestern winds. All this contributed to about a 200 million year unconformity that ended ca. 2-4 mya when sedimentation and volcanism from the Bidahochi Formation with three members totaling ca. 500 feet thick occurred covering the Chinle Formation. The volcanism in the Painted Desert added basalt debris from vents in the northwest part of the Petrified Forest helping to preserve and slow erosion of the Painted Desert. A large lake (named Hopi or Bidahochi) formed over ca. 30 percent of the Painted Desert along with other smaller lakes and lakes in the San Juan Basin and Black Mesa Basin totaling 6,200 sq. miles. Bidahochi volcanic lava flows cap many of the mesas in the Petrified Forest but much of the Bidahochi has eroded. It has been proposed that Lake Bidahochi may have had something to do with the original incision of the Grand Canyon where it overtopped it's western lake margin resulting in rapid incision and formation of the canyon. There are many hypotheses concerning this event involving the Colorado river backing up and draining to the south opening up what we know as the Gulf of California today. During the Triassic subduction along the western Laurasian plate margin of Pangea generated the cordilleran volcanic arcs throughout the Mesozoic and the volcanoes contributed an influx of ash and lava material to the Petrified Forest and the Painted Desert. Volcanoes during the late Triassic and later such as Hopi Buttes and the Navajo Volcanic Field deposited abundant ash that weathers to bentonite, a type of clay mineral that swells in mudstones that can be used for dating past geologic events. In the large area of the Painted Desert ash deposits were spread across terrestrial broad alluvial flood plains. Clymer adds, that while at the Painted Desert stop on Friday, September 8th, the vivid colors of the Painted Desert are mind blowing. Perhaps one expects a desert landscape to be predominately brown and tan, but what we found was a palette of colors. The colors change hues throughout the day with the shifting position of the sun. When low on the horizon sunlight travels a greater distance through the atmosphere and the longer wavelength blue and green components are filtered out. When the sun is high in the sky the sunlight travels a shorter distance through the atmosphere resulting in less filtering thus the longer wavelengths predominate. The shift in dominant wavelength is what causes the hues to change 32
Painted Desert. Photo by Tim Carter. There was a ranger station at the road entrance to the Painted Desert National Park. We pulled up to the window and started chatting with the ranger on duty. After a short time she asked, “Do you have any rocks?” We were taken aback, we were riding in a big red van that had GEOLOGY DEPARTMENT in bold black print on the driver’s door. It was early in the trip, so, as a matter of fact we had only one rock, which we had purchased at Bandera Crater. It was a chunk of olivine lherzolite xenolith, a variety of peridotite in a basalt matrix collected from a flow at Peridot Mesa, Arizona. She asked to see it so we pulled it out. Is she going to confiscate it, we wondered? Finding a peridotite on the surface in the Painted Desert would be about as likely as finding debris from the Hindenburg. Apparently satisfied, she gave us a piece of paper with “ROCK” hand written on it, then added a length of masking tape for which to attach the “receipt” to the rock. Apparently a group of budding geologists needed a label to assist in identifying our subject matters. We roared with laughter. Clymer continues, we went to the Petrified Forest that is composed of the Triassic Chinle Formation, the same rock units as the Painted Desert. It has rainbow tinted silica embedded logs all over the place. Tree trunks either floated down the rivers, or simply fell in. They eventually became waterlogged and sank to the bottom where they became mired in the mud. The low oxygen content of the sediment helped preserve the wood. The logs became deeply buried and over millions of years mineralized water slowly filtered through the wood depositing silica and trace minerals that supply the rainbow of colors found within the petrified wood.
33
End section of petrified log from Petrified Forest. Photo by Tim Carter.
Log pedestal, Petrified Forest. Photo by Phil Clymer. There were signs all about, NO COLLECTING! It was obvious that they were serious about enforcing this. We sighted a ranger on horseback stationed behind a stone wall. The height was such that his binoculars just cleared the top of the wall. From the other side all you could see was a ranger hat sitting on top of a pair of binoculars. He was viewing a group of tourists a number of yards away. We saw no cavalry charge but would not have been surprised had someone tried to pocket a piece of the precious wood lying loose on the ground. The visitors’ center had a large exhibit of letters and petrified wood samples mailed back to the Park from guilt ridden former visitors.
34
Tim Dalbey beside petrified log. Dalbey considers that, after Chambers AZ, we entered the Petrified Forest National Park on our way to Holbrook AZ. The Petrified Forest is a small southern area of 230 sq. mi. at the south end of the larger Painted Desert (7,500 sq. mi.) at elevations from 5,200 to 6,200 ft. asl. Most of the above descriptions about the late Triassic Chinle Formation that apply to the Painted Desert, also apply to the Petrified Forest, except more of the vegetation (ie. tree trunks, etc.) of the Petrified Forest is concentrated in this small area, often confused with the Painted Desert. The Chinle Formation outcrops of the late Triassic were deposited 205 to 227 mya. The colors are from the mineral elements in the sediments that contain iron, magnesium oxides, that occur in the mudstone, siltstone and sandstones mixed with volcanics. The colors range from the whole gamut of reds, maroon, pink, orange, brown, tans, gray, gray-white, to black. The stratigraphy in the Chinle Formation listed above are all made up of terrestrial clays, silt, sand and volcanics (ash, tephra) ca. 1,700 feet thick deposited when the global climate was warmer (mean temperature then estimated at 25º C or 77º F, current mean global temperature is ca. 14º C or 57º F). The "badlands" topography is the result of climate on the alternating layers of fine grained relatively soft and coarser grained sediments among more resistant rock. Sandstones, conglomerates and lava flows resist erosion forming low elevation cliffs and mesas. The less inundated cemented sediments erode rapidly and produce sloping hillsides with talus that cover underlying stratigraphy. The sediments in the Chinle Formation were deposited by streams meandering across a broad floodplain of low relief. The streams originated from the south southwest in the mountainous Mogollon Highlands that existed offshore during the late Triassic. The streams flowed from the volcanic uplands carrying sediments to the area of the Petrified Forest, further north and northwest the sediments were deposited in an inland lake. This area in the Triassic was broad and flat with low relief with volcanic maar-diatremes that 35
were part of the Hopi Buttes and Navajo volcanic fields. Extinct conifer trees Araucarioxylon arizonicum grew up to 200 feet tall with ca. 10 feet diameter trunks in the uplands and on the slopes that were washed into fluvial flatlands. Most of the colorful large fossilized sections of tree trunks we see lying on the surface are from the large extinct conifers mentioned above that became buried in alluvium. The colors come from permineralization or petrification that may have been fairly rapid but through time and burial the organic cellular structure of the wood is replaced. Upon aerial exposure and oxidation, the various minerals turned color to their oxidized state: (white and tan silica dioxide, all shades of red - iron and goethite, black - carbon [wood] or pyrite + iron [hydrogen sulfide], black, purple and blue - manganese oxide, green - very rare from reduced environments of chlorine - iron hydroxides). The colorful petrified logs and tree trunks are often considered chalcedony and there are also rarer opaline, jasper, and translucent agates. The entire area has been downcut by small dendritic flash flood streams that deposit their alluvium at the base of slopes all part of the Puerco River (translated from Spanish meaning "dirty" with sediment) system in the park. The larger Painted Desert and the Petrified Forest within are eroded by the Puerco River system that flows southwest from Gallup, NM downcutting through the Defiance Plateau as discussed above. To the west of the Petrified Forest and to the north of the Painted Desert an area of badlands called the Hopi Buttes Volcanic Field occurred in the late Miocene. Within this arid plateau area the topography consists of red sandstones, shale and mudstones, buttes capped by lava flows. These flows are from a large 1,200 sq. mi. monogenetic, lava field that includes small cinder cones along with ca. 300 maars (small low relief broad volcanic craters where magma and ground water collide causing violent steam explosions), and diatremes (gaseous explosions when molten magma rises through a crack in the bedrock and contacts groundwater causing vapor and gaseous explosions). The Petrified Forest is a showcase for enabling paleontologists to get an idea of what life was like in the late Triassic. The great quantities of petrified wood and fossils tell the story of conditions more than 200 mya (225-205 mya). Conditions were such that large quantities of tree trunks, cycads, ferns, fern fronds, leaves, other plants, plus animals were preserved. Tree leaves, cones, reproductive organs, ovaries, and other smaller parts of plants were preserved by compression but this was a time before flowering plants. The organic material is pressed out by the weight of the sediment load that turns to rock through time. The fossil plant remains look like thin layers of carbon pressed between two sedimentary rock layers as fine layers of shale can be split open revealing fossil leaves. The larger tree trunks, bones and teeth of animals are porous, and voids are filled with liquids that carry silica in solution. The sediments that eroded down from the southern and western mountains to form the Chinle Formation created swampy conditions that prevailed where organics would get buried in the swampy soils and oxygen was depleted that retarded decay. The silica in solution percolated into the pores of the tree trunks and formed minute crystals of quartz. The quartz solution filled the cavity and duplicated the original microscopic structure of the wood tissues. In some cases cell walls broke down and the crystals were larger forming larger crystals in the cavities, where amethyst, other quartzes, and other semi-precious gemstones were formed. The colors in the petrified logs most likely came from iron in 36
solution providing many of the colors discussed above. We wandered through the amazing chunks of the petrified tree trunks, walked some of the trails, went to various vista views, took many photographs, then went to the visitors center before we left for the day. At the center, Dalbey bought a Petrified Forest T-shirt that depicted a herd of Triceratopsians running from some predator. The depiction on the T-shirt was before what we know now about dinosaur evolution and the ceratopsian critters that roamed the landscape millions of years later in the Cretaceous. Clymer adds, that the stop on Friday, September 8th at Winslow, AZ we spent the night in a campground, “taking it easy.” He suggested, “we park the van and get out and stand on the corner.” He explains, “the fellows looked at me like I had lobsters crawling out of my ears.” They didn’t catch the meaning, “you know, like in the song, Well, I’m standing on a corner in Winslow, Arizona.” The song, “Take It Easy,” had been released by the Eagles earlier that year. It was written by Jackson Browne and Glen Fry of the Eagles. Jackson had been stranded in Winslow when his car broke down so the song was based on a personal experience. Winslow has created a tourist stop pertaining to the song at the intersection of Kinsley and 2nd Street, in the beautiful downtown district. They painted a huge Highway 66 logo on the pavement and placed a bronze statue on the north corner of a man holding a guitar. A sign was erected that reads, “Standing on the corner.” They have constructed a stop for tourists to take selfies in front of the ‘Standing’ sign. Dalbey continues, the next morning Saturday, September 9th, we departed Winslow, AZ for the privately owned National Natural Landmark designated in 1967 as Barringer Crater (aka. Meteor Crater). We drove west on I-40 ca. 20-30 miles, and a five mile road south of I-40 reaching the crater in about a half hour. The group hiked to the bottom of the crater for a photograph. The elevation at the rim is ca. 5,600 and the bottom is 5,200, about four hundred feet to the bottom. The crater represents an impact crater that hit the area ca. 50,000 years ago during the Pleistocene impacting the local bedrock. The meteor impact penetrated ca. 700 feet down into the quartz rich Coconino Sandstone, since then the crater has been infilled with eroded sediments. The pressure and high heat from the kinetic energy by the impact altered the silica in the sandstone to coesite and stishovite, both polymorphs of quartz found at the crater. The sandstone is Permian in age. According to estimations by Shoemaker, an astrogeologist, the meteor was traveling about 136,000 mph at impact. The size of the meteor mass was estimated at 81 feet in diameter and left a crater about 0.8 mile in diameter and three miles in circumference. The meteor vaporized inside the crater. The high pressure SiO2 polymorphs (coesite, stishovite) were found as spherules after the Fe and Ni (nickel) had vaporized. Upon impact the Permian sandstone beds were thrown up and over forming the crater rim 150 feet higher than the surrounding surface. This caused reverse stratigraphy with the older Coconino Sandstone (Middle Permian) boulders on top of the rim. Blocks of earlier Coconino Sandstone were thrust out (see freehand pen sketch in notebook) and over the later younger Moenkopi Sandstone (Early to Middle Triassic) and the Kaibab Limestone (Late Permian) debris.
37
Meteor Crater, south rim. Photo by Tim Carter. After the impact the Coconino Sandstone had as much as 17 percent coesite. Coesite is produced at 450 to 800 degrees centigrade (C) under 38,000 atmospheres (atm) of pressure while stishovite forms at higher temperatures and pressures both unique to Meteor Crater. Stishovite is a high density form of silica and has been synthesized at 130,000 atm pressure with temperatures as high as over 1,200 C. The importance of these minerals from the crater have also been detected on the moon. This explains and reinforces the interpretation that the craters on the moon are from space meteor or asteroid impacts. We walked around the rim for a mile or so, blocks of sandstone all different sizes, some the size of tool sheds were thrown up on the rim, up to 150 feet high above the surrounding surface. We found iron and magnesium oxidation, geodes of quartz, but meteor fragments were not found. We descended the crater and met up at the bottom where some drilling rig material had been left at a drilling site and remains of an airplane that was in a crash were also piled up in this location. We ascended the 400 foot incline of the west side sloping wall of the crater and rested, then we got back to I40 and proceeded to Flagstaff, AZ for lunch. From there we headed north on Hwy. 180 across the San Francisco Plateau headed for the south side of the Grand canyon where we camped on the South Rim of the Grand Canyon (GC) Saturday night the 9th. After lunch we left Flagstaff heading northwest on Hwy. 180 through the Coconino National Forest consisting of desert scrub at lower elevations ca. 2,500 ft. asl, higher slopes are covered with evergreen forests and Ponderosa Pines up to the tundra line at highest elevations. As we travel through the forest we are traveling over the Permian age Coconino Plateau, a sub-plateau of the larger CP that is an uplifted block formed by the aeolian cross-bedded Coconino Sandstone Formation. As we go north of Flagstaff we can see Mt. Humphrey over 12,500 ft. asl, the highest peak in AZ. It rises 38
above all the other high peaks of the San Francisco Mountains (named by missionary Franciscan friars to convert natives when they came to the area in the 1600’s, named after Saint Francis of Assisi). Mt. Humphreys and surrounding high peaks, glaciated during the Pleistocene are eroded remnants of a cinder cone stratovolcano caldera that may have been over 16,000 ft.asl and part of the San Francisco Monogenetic Volcanic Field. The basalt caldera began forming ca. 1 mya as part of the older basaltic, dacite, rhyolites, andesites and other high silica content tephra ejecta from lava domes, small cinder cones, and ‘A’a ‘Aa’ lava flows over the Permian sandstone. The monogenetic lava field began ca. 6 mya on the southern edge of the Grand Canyon Section of the CP and contains over 600 volcanic eruptions since ca. 3 mya as the plate moved over a “hot spot” plume deep in the mantle. One of the latest eruptions in the lava field occurred ca. 1,200 years ago a short distance east of Mt. Humphreys where a linear fissure spewed lava forming Sunset Crater forming a 1,000 foot high scoria (cinder) cone and ‘A’a ‘A’a lava flows. At Grand Junction we turned north onto Hwy. 64 through more of the San Francisco Volcanic Field and entered the Kaibab National Forest towards the South Rim of the GC that took 1.5 hours over 80 miles from Flagstaff. To the west of Hwy. 64 is the small Havasu Creek, a northward drainage with several waterfalls that meets the Colorado River a short distance west of Grand Canyon Village. To the east, lava capped Red Butte can be seen ca. 1.5 miles east of Hwy. 64 rising ca. 1,200 ft.above the plateau and contains the only eroded outlier remnant of Mesozoic deposition of Moenkopi sandstone and conglomerate above on the plateau. The elevation of the Coconino Plateau rises to 6-7,000 ft. asl except for the mountains described above. Bedrock is mostly Tertiary volcanic rocks from lava flows covered with Quaternary alluvium and a rolling topography with some steep 100-400 feet deep valleys dissecting the plateau. The Cenozoic and most of the upper Mesozoic sediments have been eroded away that began ca. 65 mya and lasted to ca. 35 mya. We are crossing the CP that was most likely uplifted during the last tectonic activity during the Laramide Orogeny late in the Cretaceous into the early Cenozoic. The Coconino Plateau was drained by two separate riverine systems. The Hualapai River drains the west part of the plateau while the Upper Colorado River drains to the southeast. For a conceptual perspective the Colorado River Basin watershed has been broken up into two sections near the Glen Canyon Dam. The Upper Basin watershed consists of the states of UT, WY, CO, NM. The watershed essentially captures the drainage from all the rivers in the Colorado River Basin north of the confluence of the San Juan River with the Colorado River. The Lower Basin captures all the drainage in the Colorado River Basin watershed west to south from NM, AZ, NV, and CA from the Little Colorado River westward and south to the Gulf of California. In a very simplified model outlined below the Colorado River formed through tectonic activity, faulting, uplift and erosion in the Miocene in the last 6 million years, some argue in the last 10-70 mya. Additionally, even though deposition occurred for most of 250 million years during the Mesozoic Era and the Cenozoic Era these deposits are mostly missing in the Grand Canyon from erosion except for remnants of the uppermost Moenkopi Formation to the very east and west part of the canyon. Uplift of over 2 miles (10,500 ft.) during the Laramide Orogeny created the bedrock for the Colorado River to erode the GC exposing ca. 40 bedrock 39
formations that range in age from 2 bya at the bottom to 200 mya at the top. On the north side of the canyon seven large fault blocks, for example Kaibab Plateau, differentially uplifted bedrock with major faulting created high sub-plateaus of the CP exposing bedrock to erosion creating fantastic canyons and outcrops. The sedimentary bedrock of the Mesozoic and Cenozoic reflect sedimentary deposition from orogenies in the Panthalassic Ocean off the coast of supercontinent Pangea and after breakup where deposition in various forms of foreland basins were infilled by continental sediments. In the Black Mesa Basin east of the Coconino Plateau uplift occurred west of the Little Colorado River canyon that carried the drained eroded sediments from the tectonics in the Defiance Plateau northward into the Black Mesa Basin. Continued tectonic activity to the southeast caused more uplift, faults and monoclines on the east part of the Coconino Plateau blocked the northward drainage of the Colorado River causing water to be backed up creating Lake Bidahochi as discussed previously where the Painted Desert is located. Continued uplift and westward tilting of the Coconino Plateau caused more headward erosion of the Hualapai River. The continued erosion of the Hualapai Valley worked eastward eventually through fault movements, downward tilting of the plate on the east part of the plateau, eventually created an east to west corridor that bisected the plateau. This enabled the Hualapai River and the Little Colorado River to form a new channel across the plateau and the lake was drained through the newly created channel to the west ca. 3 to 10 mya. This caused much of the Cenozoic to be eroded from the plateau. Volcanics in the San Francisco Volcanic Field affected the rivers erosional force at various times by damming flows, rerouting flows leading to widespread erosion. On the evening of Saturday, September 9th, Clymer was impressed by the magnitude of the Grand Canyon when we arrived that evening at the South Rim, he commented, “the Grand Canyon, what can you say about a world-class hole in the ground?” On repeated trips to the South Rim, we witnessed carloads and busloads of noisy tourists hurrying to the overlook only to be rendered mute when reaching the rim, as were we. The vastness of the canyon and the radiant colors overwhelmed the senses. We, being geologists, standing on the edge of another precipice, were once again compelled to advance to the bottom! We chose the Kaibab Trail for the descent on Sunday September 10. It is shorter and steeper than the Bright Angel Trail. Kaibab is six and a half miles long with an elevation change of 4,800 feet. The Kaibab is the more direct route and has fewer view obstructions. The trail is well supplied with signs marking the numerous geological and cultural points of interest. Carter recalls, hiking down this steep trail, “days before,” Dr. Larsen warned us all to clip our toenails. Failure to do this would result in severe discomfort as the trail is so steep that your toes get jammed into the front of your hiking boots. It was sage advice.
40
Permit dated Sept. 10 for overnight in Bright Angel Campground at the bottom of the canyon. Photo by Phil Clymer.
Grand Canyon South Rim. Photo by Tim Carter. We worked the geology as a group on the descent to the approximate top of the inner gorge and then broke into small groups to complete the hike to Phantom Ranch. We worked the inner gorge geology on the way out the following morning. Dr. Larsen would stop from time to time to explain the rock sequences and contacts along the trail and we would take out our 10X hand lenses (loupe) and look at the magnified sand grains for glauconite or the inside of xenoliths.
41
Illustration courtesy of the Department of GeoScience - University of Iowa
Indian Gardens, top of the Inner Gorge. Photo by Phil Clymer.
42
Yucca plant near Indian Gardens, at top of Inner Gorge. Photo by Tim Carter Carter adds, being tired and hungry crossing the pedestrian suspension bridge over the river, “it was only about 1/4 mile from the bridge to the small side canyon that led to Phantom Ranch.” It was blazing hot and got hotter the closer one got to the river. Phantom Ranch is generally 25 degrees warmer than the ground surface at the South Rim simply due to the elevation ca. one mile lower and the increased thickness of the atmosphere.
View of the Kaibob trail suspension bridge from inside the inner gorge. Photo by Tim Carter. 43
We overnighted Sunday, September 10 at the Phantom Ranch Campground. Much to our delight we discovered a small cafe where food and drinks could be obtained. There was NO CARRYOUT! Something the Park Service takes very seriously is trash at the bottom of the canyon. Everything carried in also has to be carried out, including empty Coors cans. We slept under the stars that night tucked against the canyon wall on a gravel and sand point bar above Bright Angel Creek that fed into the Colorado River. Clymer recalls, the Grand Canyon Park has a policy against collecting fossil, mineral, or rock specimens. This is a dilemma for geologists as these things are our bread and butter. We understand and respect the ban on fossils and minerals, such as the wood at Petrified Forest, but a chunk of the 1.7 bya Zoroaster granite from the bottom of the canyon isn’t likely to appear on anyone’s inventory list and will hardly be missed. So, “I
A fist sized sample of Zoroaster Granite borrowed from the bottom of the canyon. confess! I carried out a fist size piece of Zoroaster granite. It remains to this day one of my favorite possessions. They can have it back when I die.” We commenced the hike out the morning of Monday, September 11th using the Bright Angel Trail. It is just over 15 miles in length with an elevation change of 4,500 feet. Once again, all the geological contacts were well marked, and there were several much appreciated water stations. As I recall the hike took us at least eight hours. Most of us celebrated at the Bright Angel Lodge with a steak dinner that evening. Dalbey writes, we spent Monday night September 11 back at the Grand Canyon campground and headed toward Zion the next morning, Tuesday, September 12th traveling east to Marble Canyon Gorge and the Little Colorado River Overlook. We then turned north and crossed into Utah, making a brief stop at the Glen Canyon Dam. Clymer comments, Tuesday, September 12th the primary feature of Zion National Park, Utah in the Pine Valley mountains is a 15 mile long, 2,500 ft. deep canyon, carved into the Jurassic age Navajo Sandstone by the North Fork of the Virgin River. There is a two-lane road that leads to the bottom of the canyon and includes a tunnel over one 44
mile long that is carved into the sandstone of the cliff face. We camped at the facilities at the bottom of the canyon. The spectacular cliff faces are created by erosion along fracture traces (like the “Three Patriarchs” in the photo below). In the photo, the top layer is the latest Jurassic white sandstone Carmel Formation eroded, broken up, and barely seen. Below is the thick Late Jurassic light colored cross-bedded Navajo Sandstone representing the largest erg (desert) ever on the planet (up to 7,000 ft. thick) during supercontinent time of Pangea. This conformably overlies the thick reddish pink Kayenta sandstone partly hidden by the thick talus slope. The dark red thin bedrock below represents the thin Moenave Formation mudstones, siltstones and sandstones of the lowest Jurassic deposited on the Chinle Formation (end of Triassic) erosional surface after the great P/Tr boundary unconformity of 10-17 million years. It is partially hidden by tree and slope in foreground. Lower to the ground surface is the Triassic red beds of the Chinle formation. The famous Checkerboard Mesa in Zion is cross-bedded Navajo Sandstone, vertical lines are from water running down the face of the outcrop. Over time, water seeping into the fractures erodes their sides, thus widening the cracks and increasing the volume of water that can enter, again increasing the rate of erosion. We camped along the Virgin River next to a sheer sandstone rock wall for the night.
The Three Patriarchs, Zion. Dalbey continues, on Wednesday, September 13th after breaking camp we rode around Zion Canyon some more and we observed White Cliffs, West Temple rising 4,000 ft. above the valley with Kayenta Formation at the base, and the Great Arch in the Navajo Sandstone. We observed stratigraphic units of lowest Jurassic Moenave Sandstone, unconformably over the latest Triassic at the P/T boundary red beds of the Chinle 45
Formation similar to the Chinle Formation in the Painted Desert. The Shinarump Formation conglomerate with the reddish Moenkopi Formation occur below the Chinle and was a basal formation exposed in the park. In the afternoon we drove back out Hwy. 9 to Hwy. 89, turned left and drove along the Sevier fault north. Hwy. 89 runs along the Sevier River valley with steep sides 400 to 600 feet above the road created by the volcanic Markagunt Plateau on the west (left side) and the Paunsaugunt Plateau on the east side (right side) of the highway. These plateaus are part of the High Plateaus Section of the CP. We turned east on Hwy. 12 south of the Mormon town of Panguitch toward Bryce Canyon and came upon the early Cenozoic reddish, pink, tan and white eroded bedrock deposits. As we drove east on Hwy. 12 a few miles we passed through Red Canyon that is ca. 1,500 ft. deep that represents a preview of Bryce Canyon. Once inside Bryce Canyon we took Hwy. 63 south to several viewpoint vistas (Paria Canyon and river overlook, Bryce Point, Sunrise Point and Sunset Point, to name a few). Bryce Canyon occurs on the east side of Paunsaugunt Plateau at > 8,000 ft.asl. Following a Cretaceous/Eocene uplift event, the canyon represents interlocking series of sandstone ridges carved by wind, rain and the freeze and thaw of ice that formed spires, called hoodoos, that resemble chess pieces sticking upright. Once again, erosion following fracture traces are responsible for erosion creating (see the photograph above) the pillars and spires with limestone caps atop the hoodoos and spires. The host rock is the ca. 50 mya Eocene age Claron Formation (aka. Wasatch Formation). Layers slightly more resistant to erosion such as limestone, cemented sandstone, or basalt, cap the hoodoos in an umbrella effect that protects the underlying less cemented or less aggregated mudstone and sandstone layers from erosion creating the pillars and spires. After seeing all the unique spires we drove back out Hwy. 63 to Hwy. 12, and back to Hwy. 89 to go north. The late Cretaceous Kaiparowits Formation occurs below the Claron/Wasatch Formation. The formation is up 2,800 ft. thick consisting of mudstones and sandstones that were deposited on the east side of the mountainous continental island of Laramidia 100 to 66 mya. The sediments flowed into the Western Interior Seaway. The sediments are highly fossiliferous and the fossils suggest a later Cretaceous age ca. 80 to 75 mya. This formation continues and makes up a lot of the red beds in the canyons to the north along the Paria and Escalante rivers that once contained freshwater lakes. In the early Eocene uplift and faulting increased elevations and numerous plateaus, as a result the gradient was increased and streams flowed faster and cut deeper. Outlets for streams were cut off by the tectonics and sediments built up in valleys for ca. 30 million years forming lakes with deltas and sandbars. Deepest sediments turned to limestone, siltstone, mudstone to shale, and sandstone created by wave action. The lakes eventually evaporated and drained, downcutting resumed, more uplift and drainage interrupted by lava flows can be seen in and on the numerous plateaus that contain the beautiful colorful topography and canyons of central and southern Utah. Dalbey recalls, that after Bryce Canyon we continued north on Hwy. 89 through pink cliffs of the Claron/Wasatch Formation and the small Mormon town of Panguitch along the Sevier River. We stopped along the road to look at conglomerate layers of basaltic dioritic boulders. We were surrounded by the Dixie National Forest made up of Ponderosa Pine and Spruce at lower elevations changing to Fir and Aspen at higher 46
elevations. Continuing north on Hwy. 89 we travelled parallel to the Sevier Fault in a valley formed by the down side of the normal fault with an uplifted monocline created to the east by the fault. We came to the town of Circleville that is the boyhood home of notorious outlaw Butch Cassidy. The high volcanic Tushar Mountains with Delano Peak ca. 12,200 ft. asl rises above Circleville on the west. This mountain complex was uplifted as part of the Hurricane Fault that runs to the GC and lies on the edge of the High Plateau Section of the CP and the Basin and Range province to the west. We turned east on Hwy. 62 that goes through the Kingston Canyon created ca. 30 mya from volcanics creating the Marysvale Volcanic Field consisting of basalt and rhyolite. The canyon separates the north from southern Sevier Plateau. The road goes through the town of Kingston on the southern edge of Fishlake National Forest. It was getting dark and we had to find a place to camp, Hwy. 62 turns left heading north where we came upon Otter Creek Reservoir. We pitched camp in the dark, ate, and turned in for the night as it was getting cold. Thursday, September 14th, we planned to go to Capitol Reef National Monument, Utah, but our desired destination for the day was the Henry Mountains. When we awoke the Otter Creek Reservoir was covered with geese, ducks, and herons that had flown in during the night. We traveled north through Grass Valley along the East Fork of the Sevier River on Hwy. 62 to go south and east on Hwy. 24 at Burrville. Hwy. 24 goes through a valley with steep mountains on either side with Fish Lake Hightop > 11,500 ft. asl part of the Fish Lake Plateau on the east and high peaks of the north part of the Sevier Plateau on the west such as Monroe Peak > 11,200 ft. asl. As we go further east on Hwy. 24 we are going through a wide valley with the headwaters of the Fremont River. Eastward the route squeezes between Fishlake National Forest on Fishlake Plateau to the north and Dixie National Forest on the Aquarius Plateau to the south from Torrey, Utah. Hwy. 24 follows the Fremont River east towards it’s confluence with Muddy creek. After Torrey, Utah we entered the Capitol Reef National Monument (National Park status to be determined) on the north crossing the 65 mya unique S-Shape Waterpocket Fold, the largest surficial monocline (one sided) in North America. Here, we crossed the Fremont River (named after the historical John C. Fremont, explorer, military officer and politician) and it’s ca. 700 ft. gorge, part of the “Fold,” near Fruita, Utah. The geology in the monument exposes over 10,000 ft. of stratified bedrock. Beginning in the Paleozoic from 1,100 ft. of the basal Permian, Cutler Formation, to Kaibab Formation limestone, to over 2,000 ft. This is followed by the Mesozoic Triassic, basal P/Tr hiatus, then into basal Moenkopi, followed by sequential strata of the Shinarump, Chinle, an end of Triassic unconformity. The hiatus is followed by early Jurassic arid climate Wingate Sandstone, then by Kayenta Sandstone conformably overlain by huge Jurassic desertic deposits of even thicker Navajo Sandstone up to and over 2,400 ft. thick. More stratified Jurassic deposits accumulated in the stratified column including Carmel, Entrada Curtis, Summerville, and Morrison formations. The Jurassic deposition ended by a hiatus and more deposition of > 3,500 ft. followed during the Cretaceous, Dakota, Sandstones, Mancos Shale, capped by Mesa Verde Sandstones.
47
Southeast of Torrey the Circle Cliffs Anticline forms a divide for the north headwaters of the Fremont River. The “Cliffs” rise > 7,200 ft. asl due to an uplifted block creating numerous canyons on the west side of the “Fold” forming the headwaters of the Escalante Creek/River that begins to flow south on the Aquarius Plateau. There are many ephemeral creeks, gulches, and streams forming tributaries in steep canyons that drain the west dry high desert side of the Aquarius plateau where Mt. Pennell peaks over 11,400 ft. asl. The east side the runoff created some spectacular ridges, buttes, monoliths, domes (Navajo dome), towers, arches (Hickman bridge) and colorful sandstone cliffs through the “Fold” that is only 6 to10 miles wide but nearly 100 miles long. The “Fold” runs on a northwest to southeast axis through “Strike Valley” south of Canyonlands National Park to Glen Canyon. The bedrock of the whole geologic complex (listed above) can be viewed as a continuation of the Grand Canyon, Marble Canyon, Glen Canyon complex, with Capitol Reef on the north end. It is not a reef of any sort, it was named for white domes resembling buildings in the nation’s capitol and rugged peaks reminiscent of a reef. We made short stops at Capitol Reef looking at the various geologic features of the sandstones such as at Panorama Point. At this stop dark reddish brown stratified sandy siltstone beds of the Moenkopi Formation followed by the Chinle Formation multi-colored mudstone shale of the late Triassic are capped by the massive Jurassic Wingate Formation that can be seen along scenic Hwy. 24. After Capitol Reef, heading east on Hwy. 24, following the Fremont River towards Hanksville we passed through desert landscape of Cretaceous Dakota Sandstone and Mancos Shale of marine origin. The shales have eroded to form colorful eroded rounded mesas, domes and badlands of the Upper and Lower Blue Hills in the northern part of the Henry Mountains. The colors consist of blue-gray, grays to black, maroon, reds, tan, brown, yellow, to green shales, that appear blue during early morning and evening twilight. About two miles northeast of Hanksville is the confluence of the Fremont River and Muddy Creek. Muddy Creek is known for colorful slot canyons and transects the southern part of the San Rafael Swell (arch-shaped asymmetrical anticline). Together these two rivers form the saline Dirty Devil River that flows south ca. 85 miles into the Colorado River that enters the northern end of White Canyon south of Canyonlands National Park and flows through to the north end of Glen Canyon. Continuing, Thursday afternoon, September 14th, we made it to the Henry Mountains in the afternoon. From Hanksville, we drove south on Hwy. 95 entering the Henry Mountains, a range that runs between Capitol Reef on the west and Dirty Devil River on the east with Canyonlands National Park further to the east of the river. At Hwy. 276 we veered right to head further south towards old Starr Ranch and Springs our camp destination ca. 50 miles deeper into the young (25-31 mya) volcanic Henry Mountains. As we drove south past high mountain peaks to the west (such as Mt. Ellen and Mt. Pennell, both over 11,400 ft. asl) we got nearer to our camp destination for the night within view of the intrusive laccolith Mt. Hillers at an elevation of over 10,700 ft. rising ca. 4,500 feet to the north of our camp. On the way to camp we stopped at several igneous boulder fields to look at the rocks before finally stopping. Clymer comments, the Henry Mountains in Utah are composed of Tertiary age volcanics that intruded Morrison Formation sediments of Late Jurassic age. The amazing feature of the mountains is their laccolith shape. The magmatic pipes forced the molten 48
rock toward the surface but without enough force for it to break through. The molten magma intruded older sedimentary layers moving laterally between the layers forming subsurface sills horizontal to the strata and angular dykes along fissures or weak points in the older strata. The overlying rock units were forced upward and the magmas cooled into mushroom shapes from upper crustal pluton of magma pulses creating a sheeted laccolith in a short period of time. When the molten magma cooled it solidified into diorite porphyries forming Black Mesa and alkali feldspathic trachtyes at other mesas within the Henry Mountains. We were awarded some free time for independent exploration. We stumbled upon a flat dusty field devoid of any trace of vegetation, but we discovered an erosional surface that was heavily littered with Gryphaea sp., other fossils, gypsum, chalcedony, agates and quartzite. At the campground, we ran into another geological field trip group from Stanford University (California). Mike Honnert delighted the whole crowd with his infamous jungle bird calls. Dr. Larsen was within his element being in the igneous Henry’s Mountains. At the campground Dr. Larsen had spoken with the geologist leading their group and he likened some of the laccoliths features in the Henry Mountains to similar features like the huge Cocks Comb escarpment west of Escalante. Friday, September 15th, in the morning we continued exploring the Henry’s by way of a gravel road north of the ranch and spring towards Black Mesa and a nearby Cocks Comb (ca. 8,000 ft. asl) feature to the west. Both occur about 4 miles up a gravel road north of the ranch, on the east side of Mt. Hillers near the road. Black Mesa rises ca. 500 ft. above the surrounding plateau and represents a subsurface pluton where weathered rocks cover the surface with diorite porphyry mostly dark in color with abundant large hornblende phenocrysts that indicate slow cooling of the magma. Unfortunately, our time among the Henry Mountains and Black Mesa’s diorite field was cut short that morning. We had to hustle back north on Hwy. 276 to Hwy. 95 along the east front of the Henry Mountains to Hanksville where we spent the rest of the late morning and early afternoon waiting on our vehicle to be repaired. We suffered a mishap when a stone from the rough rocky road punched a hole in the gas tank of Dr. Larsen’s car. Dalbey was able to apply a temporary fix of a tee shirt wrapped around a wood spike jammed into the puncture. This slowed the leak sufficiently for the car to be driven at a rapid pace to a gas station in Hanksville, where a fiberglass patch was applied. Dr. Larsen, Mike Fein, and I (Phil Clymer) stayed with the car, with plans to catch up with the group at the next stop. We dined in a small cafe where the owner had desert landscapes painted on a canvas of sheets of mica for sale. We examined them closely, admiring the mica. The paintings were a terrible waste of mica. Dalbey recalls, by midafternoon with the vehicle repaired we headed northeast from Hanksville on Hwy. 24 paralleling the San Rafael Swell on our left (north), crossing the San Rafael River ca. 4 miles south of the junction of Hwy. 24 and I-70 (old U.S. Hwy. 50). We headed 12 miles east to the town of Green River where we crossed the Green River that flows south into Canyonlands National Park where it meets the Colorado River. We crossed the San Rafael Swell in a valley 8,000 feet in elevation of colorful Jurassic Entrada 49
sandstones. The San Rafael Swell is an anticline ca. 75 miles long on a northeast to southwest axis and 40 miles wide where Pre-Cambrian bedrock was faulted and thrusted during Laramide Orogeny forming the Rockies 50-80 mya. The San Rafael River flows southeastward draining the northern part the swell. Muddy Creek drains the southern part of the swell flowing southeastward towards Hanksville where it joins the Fremont River and both become the Dirty Devil River mentioned previously. Both rivers flow in a southerly direction draining the Wasatch Plateau to the north. These rivers have downcut through mostly Mesozoic sedimentary bedrock forming colorful slot canyons, broad canyons, washes, salt flats, cliffs, “reefs,” or steep cliffs on the east side of the swell and many other geological features. About 20 miles east of Green River we went south on Hwy. 191 at Crescent Junction towards Moab, 32 miles south. After five miles the highway follows and roughly parallels the Moab Fault Line near the road where many minor faults and fractures can be seen from the car as we descend towards Moab. These faults occur at the north end of a graben that runs south of town for miles. The fault zone represents one of many salt domal anticline structures consisting of Paleozic, Mesozoic and Cretaceous sedimentary bedrock that has moved up or down in contact with Tertiary igneous intrusives. For example, as we headed south older Wingate Sandstones (237-205 mya) on the right (west) occur hundreds of feet higher (> 2,000 ft.) than lower younger Entrada sandstones (160 mya) on the left (east). On Friday, September 15th, after having been to the Henry Mountains earlier in the day we wanted to proceed to Arches National Park (newest National Park status in 1971) and then Canyonlands National Park. The vehicle delay kept us from reaching our goal and we drove south on Hwy. 191 to Moab and found a KOA on the south side of town in the afternoon. We established our camping area and then went onto Arches National Park located ca. 5 miles north of Moab, so we went back north on Hwy. 160 and then right (east) into the park. Arches is the world’s densest collection of natural bridges and arches with over 2,000 arch features. We drove through the park on a network of roads for ca. 20 miles that lead to the arches, such as “The Windows Section” as the road passes, “Balanced Rocks,” “Double Arch,” and many trails to other arch sites. We drove north on the park road into the “Devils Garden Section,” at the north end we saw signs for trails to “Landscape Arch,” (believed to be the longest natural stone span in the world). We walked a short distance to see “Skyline Arch,” and signs for numerous trails to many more scenic sites and arches. We drove back out to go to the southern end to Park Headquarters and Visitors Center where we entered, there are several more famous landmarks, such as, “The Organ,” and “Three Gossips,” plus many more features are located along the road north of the headquarters where some have to be reached on foot. While in the park we stopped often to get out and look at many of the scenic views and formations but didn’t have the time to hike the many trails to various arches. To make a long story short, the sedimentary strata in Arches represents million of years of deposition going back to the Paleozoic Pennsylvanian Period. Over 300 mya Gondwana and Laurasia supercontinents collided creating a trough in the area of the uplifted Paradox Basin to the north filled with sea water repeatedly when the climate was warm wet and humid. The climate changed to more arid conditions and the 50
seawater evaporated. The evaporation caused the salt in the seawater to concentrate in the basin, then repeated periodic inflows into the basin carried in sediments, more evaporation and more various types of salt, anhydrite, with shales, siltstones and dolomite formed. Later, the Paradox Basin filled with sediments from open seas. The Uncompaghre Mountains were uplifted filling the basin with eroded sediments. Faulting occurred that formed troughs that contained sediments and salt. Through time and burial the more buoyant salt migrated from under heavier sediments that began to form many synclines with ridges later becoming salt anticlines. These uplifted, folded and fractured. Eventually, the weight of the deposits and subsurface heating caused layers of bedrock to be uplifted and thrusted into the salt dome evaporites causing anticlines, more faulting, and linear regions of uplift (some nearly 90 degrees) that ended ca. 200 mya.. During the Mesozoic more uplift occurred, more weight was added to basins from sedimentation coming off ranges along the coast as very arid climate regimes of desertic winds formed cross bedded sand deserts. The amount of sedimentation especially during the Middle Jurassic (Navajo sandstone) to Late Jurassic (Entrada sandstone), followed by the latest Carmel Formation that is variable, but adds up to 1,200 feet minimal thickness. More uplift occurred in the Canyonlands Section of the CP during the Laramide Orogeny 70 to 40 mya. The plate uplift caused the older less dense salt deposits to migrate into fractures and fissures in the Estrada Sandstone. Then, rainwater containing carbonic acid dissolved the granular cement and carbonates, eroding weakly bonded sand grains and enhanced dissolution of salt beds that get infilled causing weaknesses in the bedrock creating vertical fins. The overlying sedimentary rock fractured more, deformed by the anticline, as erosion migrates laterally such as in the Entrada Sandstone where most of the arches occur. Lower in the weakened zones of bedrock the sediments accumulate creating more pressure on the porous sediments and joint forms widen, more moisture accumulates and slabs collapse from their weight, or along vertical fractures creating thin ridges or fins. More moisture added to fractured sandstone is then undercut by water erosion and slabs collapse. Arches began as windows as water, wind, and frost cracking hollow out weakly cemented parent rock forming an arch that gets attacked by wind, rain, and repeated frosts rounding off the erosion. As we left the park we went south on Hwy. 191 back into Moab we drove along the Moab Fault Line that paralleled the road. Additional stream and windblown sediments were deposited over 60 million years adding to the aggregate deposit of ca. 5,000 feet that has since eroded creating the arches mostly within the Entrada sandstone. The Entrada sandstone represents dunes formed by windblown cross bedded sands deposited in an erg that were solidified. The Moab Fault Zone west of town where over 2,000 ft. of fault displacement has occurred represents one of many fault zones, including shear faults, normal faults, extension faults and others in the area. The geology of this area is complex with many structural features including folds, faults, fractures, slip zones, continues to be studied. Salt movement from deep seated evaporite layers has dramatically influenced the formation along with water infiltrating fissures and cracks aided by erosion over millions of years that has formed the
51
spectacular cliff faces and arches within the park. We spent the night of September 15th at the KOA in Salt Valley, Moab that we had set up earlier upon arrival at Moab. Saturday, September 16th, Canyonlands, Dalbey remembers that we left the Moab KOA and headed for Canyonlands about 25 miles to the southwest. The Moab area is a big mining area for salt, potash, sulfates, and uranium (Madame Currie's uranium came from here). During the Pennsylvanian Period evaporite deposits west of Moab were created by uplift cutting off drainage of an inland sea later buried by wind-blown sediments Clymer explained that Dr. Larsen was a licensed pilot. He had arranged the rental of a Piper Cub four-seat plane. It seems improbable now, but we rented the plane for $15 an hour. The first group took off about 8 A. M. At that early hour the heat spirals rising from the desert had not yet formed. The later riders experienced some strong turbulence as the land surface heated. Dalbey recorded that Dr. Larsen flew the plane and the group took turns in teams of three flying over the Canyonlands high plateaus cut by the Green and Colorado rivers. Flying over Canyonlands is one of the best ways to see and understand what the geology is like. We then flew over Arches National Park, then eastward over the Dolores River, observing canyons, fluvial deposits, and a faulted valley delineating a graben where Moab is located. Then, we turned southwestward to Dead Horse Point State Park, flying over an anticline west of Moab to Upheaval Dome that is being eroded in the center where the least resistant sediments are located.. The aerial view of Dead Horse Point is of colorful sedimentary geologic formations from past marine, desert, and freshwater environments.
Air photo of Upheaval Dome, Canyonlands National Park. Photo by Phil Clymer. 52
Clymer adds, the Upheaval Dome has been explained by two different methods. Relying on the known presence of deep-seated evaporites, it has been called a salt dome. Seismic data interpretation plus the presence of high pressure polymorphs of silica suggest it originated with a meteor strike. The later is currently the favored theory. Steep escarpments from faulting occurs in Upheaval Dome (Canyon), flying west and south over more exposed uplifted vertical and tilted layers of rock from faulting, looking south down the escarpment of the strike and fault of a graben. We flew southward over "Horseshoe Bend" in the Green River over several views of upwarped salt deposits dissolved out of early Permian strata. We flew over a commercial salt and potash facility that was using the floodplain for drying the deposits. Continued flying in a southern direction over cliffs of "stepped" topography cut by the Colorado River, is another large "horseshoe" bend of a 270 degree meander loop. North of the confluence, “Overlook Point” provides a view where the Green and Colorado rivers merge, forming Colorado River that cut the deep Cataract Canyon above Lake Powell. We flew to the
Approximate path of airplane tour. 1) Canyonlands Airport, 2) Dolores River, 3) Deadhorse Point, 4) Upheaval Dome, 5) Confluence of Green and Colorado Rivers, 6) Land of Standing Rocks, 7) Potash mine. 53
west side of the Colorado River over the "Land of Standing Rocks," and then made a loop southeast towards “Horse Canyon,” and then returned to the airport after an hour and 25 minutes in the air. The next group was waiting when we landed. Clymer, continues describing the plane tour, “the plane ride was especially exciting, for it was my first time in an airplane of any kind. We flew over both parks getting the elevation advantage of expanded vistas. I was especially impressed by a potash mine, at Canyonlands, that was the most spectacular feature I saw that was actually manmade. The potash mine extracts the mineral from the salt layer by solution. The outflow is pumped to the surface into storage tanks resembling huge swimming pools, where the water content is allowed to evaporate. A grouping of these pools was located on top of one of the mesas. The effect was surreal. The stark blues and greens of the evaporation tanks contrasted strongly with the reds, browns, and oranges of the exposed bedrock. We all learned later that the blue color results from a dye that is added to the salt solution to increase sunlight absorption, thus shortening evaporation time. Canyonlands is a vast area in the center of the Canyonlands Section of the Colorado Plateau. Four rivers flow through the area from the Fremont River in the west we saw from Capitol Reef to Hanksville. Muddy Creek flows to Hanksville from the northwest and together the two rivers combine to form the Dirty Devil River that flows south into the Colorado River in Cataract Canyon at the south end of Canyonlands. The Green River flows south from the Book Cliffs and Rafael Swell into the Colorado River. The Colorado River flows west out of Colorado, and southwest past Moab, south through Cataract Canyon to the Dirty Devil River at Hite. From here the Colorado flows southward through the narrows of White Canyon south of the park where the river flows into Lake Powell. Canyonlands is a vast area of over 500 sq. mi. divided into three areas: Island in the Sky, The Needles in the southeast with hoodoos, fins and arches, and the The Maze on the west. Where the Green and Colorado rivers converge is also considered a notable area with impressive river canyon overlook views and trails from Grand View Point and the Green River Overlook. The red and white bedrock seen at The Needles and in White Canyon areas is 250 to 500 ft. thick. The reddish brown Cedar Mesa Sandstone/Cutler Formation formed from cross-bedded coastal dunes sediments eroded from the Uncompaghre Mountains during the Permian. The Cedar Mesa red beds overlie an unconformity of the Elephant Canyon Formation providing quite a sharp color contrast with the light grayish white dolomitic sandstone, limestone and siltstone. The Island in the Sky area is in the north nearest to Moab with a visitor center, campground, spectacular rim views of numerous deep canyons, folds and
54
faults Including Upheaval Dome. The Maze is the most isolated area filled with a myriad of canyons. Much of the sedimentary geologic history of Canyonlands National Park covers ca. 150 million years of geology similar to the geology of Arches National Park described above as they are close together. Like Arches, Canyonlands is on top of a 3,000 ft. thick salt deposit from the Pennsylvanian Paleozoic seas. Cumulatively, from north Arches to southern Canyonlands the distance is ca. 160 miles that we saw from the air on our flyover. After the end of the Triassic extinction event massive early Jurassic Navajo Sandstones ca. 200 to 195 mya make up large cliff walls of white, pink to red to tan (iron oxides). The cliff walls are up to 2,300 ft. high of cross-bedded sandstone, arches and windows, salt deposits from the enormous erg (desert) that formed across the landscape. The Carmel Formation forms a thin deposit from marine siltstone, shale and sandstones above the Navajo Sandstone deposited in the MidJurassic followed conformably by massive Entrada Sandstone as in Arches. Entrada Formation is made up of beach sands, mudflats and sand dunes, reflecting arid desert conditions around the Sundance Sea in later Jurassic times. It consists of arches, bridges and shear cliff faces in red silty sandstone that can be 1,000 ft. thick. About 70 mya the area uplifted during the Laramide Orogeny and the later formations like the Morrison at the end of the Jurassic have been eroded. Dalbey continues, while we were flying the rest of the group traveled to the east and southeast of Moab 40 miles to Manti La Sal National Forest in the La Sal Mountain Range. These mountains with peaks over 13,000 feet were formed by igneous intrusions contemporaneous with the Henry Mountains intrusions. We stopped along mountain roads and collected quartzite, tuffs, breccia, conglomerates, sandstones, diorite, syenite, and porphyries with small hornblende crystals and large white feldspar crystals. This was our last day in Utah, after the flight reconnaissance over Canyonlands, and sample collecting along roads in the La Sal Mountains, we gathered everyone in Moab and headed back north on Hwy. 191 to reach I-70/Hwy. 50 to go east to Grand Junction, Colorado. (Side note: unfortunately, we did not take the scenic and geologically stunning Hwy. 128 north through the Colorado River Gorge for ca. 45 miles from Moab to Cisco, Utah and then go northeast to Hwy. 50/I-70). As we traveled east from Cisco, I-70 runs between the eastern part of the high Book Cliffs on the north and the Uncompaghre Plateau to the south. The Book Cliffs represent mostly uplifted Cretaceous age (ca. 100-55 mya) stratified sandstones and shales. The Cliffs contain significant coal deposits from marine sequences with sedimentary bedrock as high as ca. 9,000 ft. asl such as Pike Ridge north of Mack, Colorado. Interstate 70 passes through the south end of the Douglas Arch at the town of Mack, Colorado at the northern end of the Uncompaghre Plateau with Mesozoic bedrock Black Ridge Canyons and wilderness areas a few miles to the south. Pinon 55
Mesa over 9,500 ft. asl and the Uncompaghre Mountains could be observed off in the distance to the south. The plateau was arid with exposures of Upper Cretaceous Mancos Shale at the state line to lower sequence Dakota Sandstone outcrops as we arrived at Grand Junction in the Grand Valley of Colorado. The Colorado National Monument is located less than 5 miles west of Grand Junction and commemorates the Colorado River. The monument consists of Jurassic age Wingate Formation sheer cliffs (similar to cliffs we saw in Aches National Park) with Chinle Sandstones below including faults from uplift, a monocline, and Precambrian gneisses and schists that were exposed during the Uncompaghre uplift in the late Palaeozoic and again in the Laramide Orogeny. At Grand Junction we crossed the confluence of the Colorado and Gunnison rivers and went ca. 45 miles southeast on Hwy. 50/I-70 to Delta, Colorado. We passed through Cretaceous Mowry Shales below thick Frontier Sandstones deposited over 7,000 feet thick, all capped by Mancos Shale and Mesa Verde Sandstone including shales. These formations were deposited from 130-70 mya when an inland shallow “muddy” Mowry Sea (aka. Western Interior sea [WIS]) existed at the northern part of a much more expansive sea. The WIS was larger and deeper than the Jurassic Sundance Sea 60 million years earlier that occurred in much of the same area as described earlier in this geologic log. Part of the WIS was located in the Uinta Basin as sediments from the northwestern Uinta Mountains filled the basin with later clastic sediments of over 7,000 ft. that formed the Frontier Formation. Structurally, there are over ten major anticlines, synclines and faults along the “Grand Valley” where the Colorado river drops ca. 500 feet in elevation from Grand Junction, Colorado to Moab, Utah, a distance of ca. 100 miles. As we drove southeast on Hwy. 50 from Grand Junction we passed the “scenic route” Hwy. 141 that passes through from east to west the dry Unaweep Canyon that bisects the Uncompaghre plateau where Precambrian bedrock is exposed. The road eventually crosses the north flowing Dolores River at the town of Gateway (CO) on it’s way northwest to the confluence with the Colorado River at Dewey, Utah north of Moab. We saw the confluence while flying our aerial reconnaissance over Canyonlands and Arches in the Moab area. Further on Hwy. 50, on the right, we passed the road to Escalante Canyon at Delta, Colorado in the Uncompaghre National Forest. As we drove towards Delta, Colorado on the right (west) we drove along a huge private land holding and BLM tract of land as we entered into the north part of the Uncompaghre National Forest. At the town of Delta we passed by a road that led southwest into Dominguez/Escalante canyons that consists of 1.4 to 1.8 bya Proterozoic gneisses, schists, granites, amphibolites, to name a few of the very old rock types that have been uplifted and overlain by Mesozoic bedrock. We passed by these canyons because we had run out of time and had to travel twenty-two miles further southeast, well into Dakota Sandstone territory on Hwy. 50 where we finally stopped at Montrose, Colorado to camp for Saturday night the 16th. Sunday, September 17th, Clymer writes, that the Black Canyon of the Gunnison (BCG) National Monument has been eroded by the Gunnison River following a series of tectonic events and is made up mostly of Precambrian gneisses, schists, and 56
igneous rocks followed by Mesozoic to Cenozoic sedimentary bedrock. It is busily grinding its way deeper, as the river has a steeper gradient than the Colorado in the Grand Canyon. The BCG currently is ca. over 2,500 feet deep in places, and the sides of the canyon are so steep that some parts receive only minutes of sunlight each day. We viewed the BCG from the scenic overlooks within the national monument. About 67 years ago, ca. 5 to 10 miles east of Montrose along the Gunnison River engineers blasted, excavated, and created the Gunnison Tunnel ca. six miles long through Vernal Mesa east of Montrose. The tunnel at a depth of 2,000 ft. In the canyon was oriented in a southeasterly direction so that water from the Gunnison River would flow into the arid Uncompaghre River Valley. The Uncompaghre River was low flowing in the summer months and could not be used for agriculture. The irrigation from the water provided by the tunnel made it possible for agriculture to flourish in the Uncompaghre Valley and the town of Montrose to grow.
Wall of the Black Canyon. Photo by Tim Dalbey. Dalbey continues, we left the Montrose campground in the morning of the 17th heading for (BCG) National Monument. The monument was not as well developed as other monuments and parks. The monument was of keen interest to a "hot rocker" (one who studies igneous rocks) like Dr. Larsen. He got into to a long discussion about 57
metamorphism and metasomatism regarding the BCG. The park literature was not nearly as clear about the magmatism that occurred in BGC as Dr. Larsen, but it turns out BCG was one of the premier igneous and metamorphic showcase locations of the trip with nearly 2,250 feet of vertical exposures. We drove over rolling topography entering the south rim of the canyon at Tomichi Point on Hwy. 347 overlooking the sheer bedrock walls of the canyon running east to west. Bedrock in the canyon consists of the Proterozoic (metamorphic and igneous), late Jurassic (sedimentary), Cretaceous shales (sedimentary), and Tertiary (sedimentary capped by volcanics) from Montrose to Gunnison. The plateau has been uplifted several times and the Gunnison River now cuts through younger deposits. The canyon represents a geologic cross-section of a mountain turned on its side exposed from uplift/faulting/folding with pinkish to white pegmatite, angular intrusives, all mostly horizontal. We drove along rim road to the “Painted Wall” that consists of a sheer vertical rock exposure of more than 2,000 feet representing 1.8 billion years of basement rock of the Proterozoic (aka. Precambrian). The “wall” is composed of igneous and metamorphic dark reddish brown gneisses, schists, granites, gabbros, diorites contrasted by igneous pinkish/white pegmatite bands of muscovite, potassium feldspar and quartz intrusives exposed on the vertical fault/folded walls of the canyon. Above the massive angular igneous and metamorphic basement bedrock there is an abrupt change, a huge (in time) unconformity, where nearly the entire 300 million years of the late Paleozoic and early Mesozoic are missing. The Mesozoic is present with the Entrada Sandstone as we entered on the west, and the Morrison Formation known for its fossils can be seen overlying the “Painted Wall.” The Cretaceous Mancos Shale is exposed also along the road from the towns of Delta to Montrose. The inner canyon of the Grand Canyon (GC) was the only other place we went to with bedrock exposures as old as the BCG. The GC consisted of Proterozoic (1.8 bya to 540 mya) to Cambrian (540 to 485 mya) exposures but nothing like what we saw, or as large of scale as BCG. The BCG basement late Proterozoic metamorphic rock consist of "exfoliated" (bedrock that was once layered) exposures composed of banded schists and gneisses that formed as a result of tremendous stress and pressure, heat and burial, as opposed to "non-foliated" metamorphics, formed by heat such as hornfels and quartzites. Generally, dark bands in schists are mafic and light bands are felsic. The dark mafic bands consist mostly of iron, magnesium and less than 45 percent silica, while the felsic (feldspathic) lighter bands are made up of potassium, aluminum and silica as much as 65 percent. Gneisses are heated more nearing the igneous phase (800 degrees C [> 1,400 F]), where felsic bands melt and become disoriented, while mafics form straight bands. If higher temperatures occur mafics become magmatites. Volumes and multitudes of research reports have been written on the igneous and metamorphic activity that went on at BCG, but, way too lengthy to go into here, as we just touched on some of the highlights of this magnificent place. One of the outstanding features of the BCG are the pegmatites mentioned above. The darker massive canyon walls consist of igneous darker gabbros, diorites, and granites that were uplifted as seen on the north side of the canyon at the "Painted Wall.” The streaks that appear in the wall represent the best examples of pinkish-white to white pegmatite intrusives on the field trip, if not in North America, or in the world. Dr. Larsen 58
explained, “the hot magma intrusives were forced through cracks and fissures in the bedrock where the siliceous aqueous solutions cooled slowly forming the large crystals of muscovite and alkali feldspars such as orthoclase among others. Pegmatites were formed in two liquid phases, one consisting of a silica melt phase and the other an aqueous water melt phase with volatiles.” The igneous granitic pegmatite intrusives consist of magma that cools into large interlocking crystals measuring 0.5 in. to 3 ft. across (in some instances larger), mostly of quartz, potassium feldspars, and micas introduced in the late liquid magma phase. Dalbey, in his field notebook drew five sequential isometric block diagrams of how the BCG formed and we will spare the reader those details. The diagrams were accompanied by nine photographs of the Gunnison River Canyon, “Painted Wall,” the narrowness of the gorge at ca.1,300 ft. wide at the rim and narrowing to about 40 ft. wide at some points at the bottom of the gorge. The Mesozoic bedrock at the top starts with the overlying Jurassic beds that represents a huge erosional unconformity with the igneous canyon below. These strata can be seen as we headed eastward toward the town of Gunnison and the Cripple Creek mining area. After BCG we headed east towards the town of Gunnison traveling through middle Cretaceous Mowry, Frontier and Mancos formations as the 14,000 ft. high San Juan Mountains came into view to the south. These mountains formed mostly during the Oligocene when uplift occurred creating a huge volcanic field with granite batholith intrusives exposed that culminated 2 bya of orogenic mountain building and other tectonics in the area. From the road the jagged volcanic peaks appear to have been glaciated as we observed remnants of arretes and cirques. Highway 50 roughly parallels the west-northwest to southeast striking Cimarron and Red Rocks faults, remnants of uplift during the Laramide Orogeny and Gunnison Uplift exposing Precambrian rocks on both sides of the road as we go east. This valley contains numerous faults that occur in this tectonically active zone between the Southern Rocky Mountain Province and the Canyonland Section of the Colorado Plateau. East of Montrose Hwy. 50 deviates to the southeast of the Gunnison River and gorge, 20 miles later the road closes back north near the river at Morrow Point Dam. The ca. 500 foot high dam was built in the 200 ft. wide gorge in the Precambrian igneous and mostly metamorphic rock in the canyon with shear welded tuff basaltic walls lining the canyon. From the distance the dark colored canyon wall rises over 3,000 ft. forming shear steep cliffs of Blue Mesa Welded Tuff with a thickness of up to 1,000 to 2,000 ft. on the north side of the BLM reservoir. The elevation of the reservoir is ca. 7,200 ft. asl. After the Morrow Point Dam the narrow reservoir continues ca. 12 miles east on the Gunnison River. Eight miles further east on the Gunnison river the ca. 400 ft. high dam for the Blue Mesa Reservoir, elevation > 7,500 ft. asl. The dam created the second highest and one of the largest bodies of water in the state that stretches east for 20 miles almost to the town of Gunnison. Breccias, capped by tuffs appear as vertical columns that are composed of West Elk Breccias from the West Elk Mountains to the north. The San Juan Mountains to the south erupted about the same time in the Eocene ca. 35-30 mya and rise over 14,000 ft. asl. The West Elk Mountains rise over 13,000 ft. 59
asl north of the Gunnison River and Blue Mesa Reservoir. The northern part of the range consists of laccoliths that intruded Mancos Shale and mudstones. The southern part of the West Elk Mountains is different in origin as a result of a stratovolcano, ejecta, breccias made up of solidified lava, ash, mud flows, coarse rock fragments of previous volcanics, and tuff. To the south volcanic ash from the San Juan Volcanic Field added hot ash ca. 27-26 mya to the already existing tuff that was hot enough to weld the existing tuff and some breccias into more weather resistant caps on southern slopes and mesas. As we drove past the cliffs in the distance across Blue Mesa Reservoir we could see what appeared to be dark black shear cliffs eroded by the Gunnison River. The cliffs turned out to be profiles of volcanic strata that appeared in vertical columns. The columns were formed by erosion of welded tuffs known as the Dillon Pinnacles that overlies the West Elk Breccia with underlying Mesozoic sedimentary rocks. As we carried on eastward we saw more cliff exposures of welded volcanic tuffs. The entire Gunnison River corridor is part of the Curecanti National Recreation Area that also contains several national forests. We went through Gunnison and stopped east of the town along Hwy. 50 to look at outcrops near the Continental Divide in the Tomichi Creek valley. We collected metamorphic rocks, gneisses, quartzites, granites, as well as igneous gabbros, diorites and some other coarse and fine grain rocks. Sedimentary rocks were shales and limestones from mud flows. Some discussion commenced about the origin of these rocks, if they were deposited as fluvioglacial diamictons, tills or mud flows. For them to be from tillites they would have been polished and or striated, and these showed no polish indicating they didn’t travel very far from the origin, or glacier. Breccias and andesites in the area indicated volcanic origins. From here we traveled east over the high > 11,000 ft. asl Monarch Pass, with Mt. Aetna over 13,700 ft. asl on the north side of the pass, then past the Continental Divide, into the headwaters of the Upper Arkansas River Valley. The Upper Arkansas River flows southeasterly through a steep valley with the Sawatch Mountains on the west and the Mosquito Range on the east. Headwaters of the Upper Arkansas River occur north of Leadville high in the Sawatch Mountains and flows through the Upper Arkansas River Valley that is filled with glaciofluvial deposits to Salida on Hwy. 50, and on southeast through the valley. Mt. Sherman, one of the highest peaks in the Mosquito Range was glaciated and rises over 14,000 ft. asl. The glacial deposits in the valley consist of Precambrian granite boulders all part of Tertiary volcanic out flow from the Sawatch Mountains. We had passed through Gunnison National Forest, and the southern end of the Sawatch Mountains, and the very northeastern end of the over 14,000 ft. asl San Juan Mountains. On Hwy. 50 as we approached Salida, to the north we observed Mt. Antero that could be seen in the distant northwest at over 14,200 ft. asl, This is highest peak in the southern Sawatch Mountains, and over 7,000 feet above the town of Salida. In the distant north, out of sight, the higher peak of Mt. Elbert at over 14,400 ft. asl rises as the highest peak in the Sawatch Range and in the Rocky Mountains. Traveling on the west side of Salida we passed through alluvial fan deposits of unsorted glacial outwash from Pleistocene glaciers of the Sawatch range where mining companies work many of these areas north and south of Hwy. 50. To the east side of Salida we passed more mining areas. Salida was known for it’s smeltering of silver, 60
gold, zinc and lead. Salida is located strategically at the confluence of three major mountain ranges: San Juan Mountains to the southwest, Mosquito/Sawatch Mountains to the north/northwest, and the Wet/Sangre de Cristo Mountains to the south-southeast. Traveling east of Salida on Hwy. 50 towards Royal Gorge, a few miles west of Canon City, we passed through a basin (graben) traversing more volcanic dikes and fissures that were mined for minerals and gold southwest of the famous Cripple Creek Mining District. Mining companies are exploiting deposits from Miocene volcanism all through this area. The basin is filled with volcanic and non-volcanic deposits from glacial and fluvial erosion that were exposed by steeply dipping faults, then covered by welded tuffs, andesite and basaltic lahars, and flow breccias to the north from intense eruptions. We turned right off Hwy. 50 onto County Road 3A to get to Royal Gorge four miles south. At Royal Gorge Park there is a suspension bridge spanning the steep canyon eroded by the Arkansas River. There was no need to hike to the bottom of the canyon as one can admire the views of the gorge from the bridge 1,000 feet over the river. The bridge had wooden planks for the roadway and the boards were widely spaced, so that by looking through the gaps between the boards one could easily see clearly to the bottom. The chasm is about ten miles long with Precambrian igneous granites, metamorphic gneisses, schists and quartzites from 1.7 bya, that were uplifted some 5 million years ago. This was a tourist area so we made a short stop to look at the canyon from the bridge and then headed back out west of Canon City through the Grape Creek Valley.
Bottom of Royal Gorge as seen from the suspension bridge. Photo by Phil Clymer. 61
We could see Tanner Peak ca. 10,000 ft. asl at the north end of the Wet Mountains that occurs 15 miles south of Royal Gorge and 6 miles south of Canon City. The headwaters of Grape Creek are high in the Sangre de Cristo Mountains and descend the northeast side of the Wet Mountains flowing north to the Arkansas River on the west side of Canon City. The Sangre de Cristo Mountains have a very long and dynamic geologic history that is too long to go into here. But, a brief perspective on the Grape Creek Valley we observed is only a small part of the geologic history that is represented brought about during Pre-Oligocene times. The Sangre de Cristo Mountains date to the late Proterozoic (> 1.5 bya) when plates were colliding, subducting and plutons were rising causing volcanoes along with deposition and continental accretion to the plates as revealed by gneisses and granites. This was all followed by a very long unconformity (most likely erosion). This was followed by the rise of the Ancestral Rocky Mountains (ca. 325 to 290 mya) when there was uplift, troughs created between mountain ranges filled with sediments, subsidence, faults, alluvial fans, deltas into marine environments in the Late Paleozoic. This was followed by uplift during the Late Cretaceous to the Paleogene during the Laramide Orogeny 80-45 mya. Then, huge sediment deposition from Sangre de Cristo Range (northern part of Sangre de Cristo Mountains) uplifted causing more erosion adding more sediments, followed by faulting and uplift. Most of the highest peaks in the Sangre de Cristo Range were once ancient coastal or sea floor environments that were uplifted as massive faulted blocks during the Cenozoic that began 65 mya instead of mountains created by volcanoes. The Wet Mountain Valley that Grape Creek flows northward through is an intermontane graben formed within the Grape Creek Fault Zone where normal faulting occurred ca. 35-30 mya, between two ranges, the Wet Mountains on the east and the Sangre de Cristo Range on the west. The tectonics in the area cut off the north flow of Grape Valley as sediments were deposited in the ancestral valley of the Arkansas River that formed ca. 29 mya. The river flowed southeast through the Front Range of the Rocky Mountains exiting through the Canon City Embayment out onto Great Plains at Pueblo ca. 30 miles west of the Wet Mountains. We drove back north on Hwy. 3A, crossed Hwy. 50 proceeded north to Hwy 9 that took us through the west flank of the "Thirtynine Mile” Volcanic Field of igneous tuffs, andesite bedrock, lahars and lava flows that covered an Eocene erosional surface into the Oligocene from 36-27 mya. This volcanic field was just one of the many volcanic fields that make up the Central Colorado Volcanic Field (CCVF) that stretched nearly 10,000 sq. mi. The CCVF stretched from the Sawatch Mountains on the northwest to the Wet Mountains and Sangre de Cristo Range to the south, to the southeastern Front Range, and west to San Juan Volcanic Field with over ten volcanic centers, and the source of precious metals that were later mined. We passed by several high peaks of the “Thirtynine Mile” Volcanic Field that reached over 11,000 ft. asl on both sides of Hwy. 9. We passed the town of Guffy, passed Mt. Guffy over 8,500 ft. asl, on our way to Antero Reservoir by way of Hwy. 24. As we got closer to Antero Reservoir high peaks of the Mosquito Mountains could be seen to the west such as Marmot Peak over 12,000 ft. asl and East Buffalo Peak over 13,300 ft. asl. Higher peaks of the Sawatch Mountains could be seen off further to the northwest. The Mosquito Mountains were part of the Sawatch Uplift ca. 65 mya and later separated by a rift 35 mya that created the valley 62
where the headwaters of the Upper Arkansas River begin. On the way to Antero Reservoir we also passed Kaufman Ridge on the west, ca. 20 miles south of the reservoir that contains the oldest nearby bedrock. The ancient bedrock consists of complex 2.5 to 1.6 bya Paleoproterozoic biotite gneiss and 1.6 to 1.0 bya Mesoproterozoic granodiorite and granites.
Antero Reservoir. Photo by Tim Carter. Monday, September 18th, it was already beginning to snow in the higher altitudes of the Sawatch Mountains. Monday morning as we left the Proterozoic volcanic bedrock (2.5 to 0.54 bya) area of the Antero Recreation Reservoir we headed east on Hwy. 24 toward the town of Hartsel and Wilkerson Pass at 9,507 ft. asl. The pass consisted of “Puma Hills” metamorphic rocks dating back 1.7 bya within Pike National Forest. The high “Pass” consists of Puma Peak over 11,500 ft. asl and 11,300 ft. asl Badger Peak, plus other peaks that we could see to the north all part of the CCVF. Once through the “Pass,” we entered the Rocky Mountain Front Range and traveled through the town of Lake George and crossed the South Platte River on our way to Florissant Fossil Beds National Monument less than ten miles east on Hwy. 24. Areas to the west and south had been uplifting during the Cretaceous by the Laramide Orogeny as discussed above. North drainages were blocked and routed south or southeast like Grape Creek and the Upper Arkansas River Valley established ca. 29 mya routed southeast. Below, the late Eocene to early Oligocene Florissant Formation the Wall Mountain Tuffs (ca. 35 mya) cover the plateau that are part of the Laramide Orogeny that began 70 mya. The tuffs are a result of a huge pyroclastic explosion covering the area after a long unconformity. Pyroclastics originated from calderas that erupted on Mt. Princeton (mentioned above) and Mt. Etna to the west in the Sawatch Mountains north of the Mt. Antero batholith center a short distance to the south, all part of the CCVF.
63
Florissant National Monument is located on County Road 1 south of the town of Florissant. The monument is only ca. 43 miles (SW) on the windward side of Pikes Peak and 15 miles north of the town of Cripple Creek and the gold mining area where 1.5 bya Cripple Creek Granite crops out. Pikes Peak Granite is made up of coarse grain igneous minerals (quartz, biotite, feldspar [both K and Na], hornblende) that is the base rock formation in the area formed from a molten intrusive batholith 1.10 bya that cooled very slowly. An enormous erosional unconformity (1.06 bya) followed until the Wall Mountain Tuff erupted when pyroclastic flows deposited from the west covered the entire plateau enhanced by lahars containing slurries of ash, ejecta, lava, tephra, gases, pumice, cinders, silt, sand, clay, crystals as magma cooled and water vapors.
Florissant Fossil Beds National Monument, photo from 1973 trip by Phil Clymer Toward the end of the Laramide Orogeny volcanic lahars from the Thirtynine Mile Volcanic Field interrupted stream flows as andesitic magma and tuffs covered the plateau. North flowing streams were damned by lahars from the Mt. Guffy (ca. 8,500 ft. asl) volcanic eruption center 34 mya creating several shallow lakes becoming stratified shale beds with interstitial layers of conglomerates and mudstones. The estimated size of one lake had an area of ca. 36 sq. km. or, about twice the size of Caesar’s Creek Lake, 50 miles northeast of UC near Waynesville in Warren County, Ohio. The fossil layers include, diatoms and freshwater life (fish, insects, other plants and animals) that fell to the bottom of one of the lakes 12 miles long by 2 mile wide and were buried by fine clay diatomaceous sediments, ash and tuffs. There were several lake sedimentation events over the years amounting to ca. 230 ft. deep deposits with large Redwood and Sequoia trees ca. 1,000 years old and trunks 15 ft. in diameter preserved in the lowest deposits. Absolute dates indicate that some "diatom rain" went on for more or less, continually, for 5,000 years at a time for over 10 my (34-24 mya). The diatom and ash fall created anaerobic conditions for excellent burial along with the mud preserving fossil remains of over 60,000 specimens. Some these include: algae, bacilli, 64
fruits, and leaves from plants such as Sequoia tree stumps, Giant Redwoods related to the giant California species, pine, walnut, willow, oak, and maple to list a few larger plants and vertebrates such as fish numbering over 200 species. From the extremely well preserved specimens, up to 1,700 species have been identified, of those over 1,500 species are insects such as bees, wasps, dragonflies, butterflies, earwigs, beetles, even Tse Tse Fly, to list a few that were buried in lake layer fine sediments. From the preserved flora, pollen and other plant remains, the climate was warmer and wetter with less seasonal variation of temperature during the early Oligocene. We left Florissant and headed east on Hwy. 24 for Colorado Springs passing Hwy. 67 that goes to the Cripple Creek gold mines to the south on our way towards Pikes Peak. The mining area is Precambrian 1.1 bya Pikes Peak granite basement rock intruded and overlain by mostly Miocene volcanic and non-volcanic rocks. The basin subsided along vertical steeply dipping faults cut by dikes and sills. As mountains uplifted from the Laramide Orogeny beginning 80-70 mya eroded sediment from the mountains filled the basin later buried by breccia and intense igneous activity that followed. Fissure eruptions with magma injections account for the mineralization. Later, mining followed the fissures to recover the gold. Then, we travelled further east through Pike National Forest towards the "Red Rocks" and Manitou Springs at the foot of Pikes Peak. Many aquifers formed in limestone along the junction of the Ute and Rampart faults where Rocky Mountain fault blocks and the Great Plains fault blocks to the east collide. Monday, September 18, Pikes Peak. We drove up Pikes Peak that was formed by a 1.1 bya from an igneous granitic intrusive batholith. Uplift during the Laramide Orogeny ca. 70-50 mya resulted in elevations over 20,000 feet in the Front Range. Pikes Peak now stands at just over 14,000 ft. asl with flanking monoclines and monadnocks formed from several erosional cycles lowering the entire Front Range. Eroded Front Range sediments formed the High Plains across the eastern Colorado Plateau and Kansas. Previously mentioned, Pikes Peak Granite is one of the oldest granites in the U.S. consisting mostly of potassium feldspar (pinkish color), quartz (gray), biotite (black) and hornblende (gray to black). We drove to the visitor center at the top of the peak and looked out from the observation area and took photographs. Dalbey added several physiographic and geomorphic illustrations of the area showing how glacial moraines, landslides, slumping, and steep erosional runoff lowered the peaks and cut deep valleys during Pleistocene glaciation. We drove down the winding road to Hwy. 24 and headed east towards "Garden of the Gods," about an hour away. Later in the day, we entered the "Garden of the Gods" south entrance towards the "Gateway" that is on the north side of Hwy. 24, northwest of Colorado Springs. The "Garden" consists of horizontally layered ca. 320 mya Late Palaeozoic (Carboniferous to Permian) sedimentary outcrops. The outcrops were faulted and tilted during the Laramide Orogeny. The sediments were deposited along a desertic shoreline that underwent deformation by the Rampart Fault, resulting in uplift that vertically tilted bedrock. The vertical bedrock was eroded through the Tertiary and were once much more pronounce. The outcrops mostly consist of red, pink, white sandstones, Mesozoic conglomerates, and limestone. Pleistocene glaciation further eroded the vertical bedrock leaving behind more resistant pinnacles, spires and fins known as: the Cathedral Spires, Three Graces, Tower of Babel, The Gateway (late Cretaceous) 65
Balanced Rock with a view of Pikes Peak looming high above the “Rock” in the background. Many of the upright exposures are of different geologic ages trending older to the southern red beds of the Jurassic Morrison Formation and Dakota Sandstone Cretaceous in age. The upright age differences come from "horsetail" and “drag” faulting (anticlines, synclines, etc.) where fractures in the bedrock splay out asymmetrically on one side from a main fault such as the Rampart Fault. We went to the small visitors center for literature on the park that was lacking. We found that the park was poorly developed, although there were trails throughout as we drove through stopping to look at the geologic features.
Thrust fault at Garden of the Gods.Photo by Phil Clymer. We left Colorado Springs later in the afternoon and headed east on Hwy. 94 driving from the Front Range into rolling topography of the Colorado Piedmont (ca. 6,500 4,500 ft. asl, spreading out for nearly 21,000 sq. mi.) as part of the Great Plains Physiographic Province (GPPP) manifested as an old erosion surface with escarpments. Erosion from arid various changing climate periods had lowered surfaces in places to expose the lower Cretaceous Dakota Sandstone that underlies the Piedmont. Sandstone is exposed on the surfaces as well as other later Plio-Pleistocene beds. The plateau along the road we traveled dips eastward dropping from ca. 5,000 to 4,000 ft. asl at the Kansas state line. A domal structure from the North American Plate deep in the subsurface below Kansas caused Cretaceous age Niobrara Formation marine limestone to warp upward forming 400 ft. high scarps towards Pueblo, Colorado exposed to erosion. The headwaters of the Smoky Hill and Republican rivers occur in the Piedmont and join at Junction City, Kansas to form the Kansas River. The Arkansas River to the south and the Solomon River cross the Piedmont to the south, as all rivers 66
crossing Kansas flow west to east. We descended from the Piedmont to the High Plains (ca. 4,500 to 2,500 ft. asl) as we crossed flat fluvial plains that were once huge alluvial fans consisting of clay, silt, sand, gravels and cobbles. The plains were all reworked and deflated by streams such as the Platte River to the north, Arkansas and Canadian rivers in the central part, and Red River to the south for 35-20 million years. The sediments were eroded from west to east from the Rocky Mountains that were in excess of 20,000 ft. asl as mentioned above. The alluvium is underlain by Mesozoic bedrock. We are heading towards Hays, Kansas and the Central Lowlands ca. 2,000 ft. asl. There is a large, several million year old, erosional unconformity cut by streams flowing eastward to southeastward out of the Front Range as described above. The rejuvenated streams downcut truncated surfaces where late Miocene into the early Pliocene (33-5 mya) sedimentary deposits filled valley cuts. The late Pliocene climate became more arid, plate upwarping in the late Miocene reduced deposition and increased erosion. The erosion resulted in deposition of Miocene to Pliocene deposits, and more later (12 mya to present) as sedimentary deposits accumulated up to 900 ft. thick. The thick deposits of alluvium represent the Ogallala Formation that covered eight states of the High Plains from what is now the Dakotas south to west Texas. The Ogallala Formation mostly consists of aeolian sediments wind blown across dry alluvial fans, or infilled playa deposits resulting in subsurface carbonate buildup forming residual caliche, marl, sandstone, agate, chert, ash, and limestone from aridity and climate warming. Due to percolation of rainwater and streams on the pre-Ogallala surface, water in the late Miocene-Pliocene deposits was retained in the sediments and created the Ogallala aquifer, one of the largest in the world spread out north to south through portions of eight states. There are several North America Land Mammal Ages (NALMA) that occur in the Ogallala alluvial clastic sediment formations starting in the Miocene. The land mammal ages consist of sequences of vertebrate faunas where the first appearance of a new species is unique to the sequence. The name of the sequence reflects the general geographic location of the fauna where they were first found in the Ogallala and begins with oldest to the youngest: Hemingfordian 19-15 mya, Barstovian (15-12 mya), Clarendonian (12-9 mya), Hemphillian (9-5 mya), Blancan fauna (5 - 2.5 mya) through the Pliocene. The Pleistocene 2.5 mya -12 kya) is the youngest that started with a warming trend that became cooler towards the end into continental glaciation sequences during the Rancholabrean Fauna. The last NALMA during Pleistocene glaciations was wide spread and reached into northern Kansas and alluvium from the glacial outwash occurred in many locations. The land mammal ages reflect early adaptations to the Great Plains flora that varied from savannah to steppic grassland environments that formed mollisols, one of largest in extent semi-arid savannah grasslands on earth reaching from high latitudes in Canada to southern Texas. In the Pleistocene the grasslands supported early mammalian forms of animals such as: horses, tapirs, rhinos, camels, cats (Smilodons [aka. Sabre-toothed cats]), bears, elephantidae, sloths, llamas, lion, to name a few. After crossing ca. 330 miles of the High Plains in six hours on Hwy. 94, the second largest geographic province in the U.S. we stayed Monday night in central Kansas at a campground outside of Hays, Kansas. The High Plains ended in a series of Ogallala deposits accentuated by 67
(Niobrara limestone Cretaceous in age) cuestas forming the Ft. Hays escarpment lowering to the Plains Border west of the Central Lowlands of the Great Plains. Clymer writes, “Flame-out in Kansas!” We decided to make an overnight stay in Ogallala terrain at a rest area astride Interstate 70 about 150 miles from the ColoradoKansas state line at Hays, Kansas. We unpacked and settled in for the night when we heard a mighty shout: “YOUR TRUCK IS ON FIRE!!!!!” A quick glance revealed flames and smoke issuing forth from the dashboard of “Old Red.” For most of the trip we had to deal with an electrical short in “Old Red.” I believe activating either the horn or windshield wiper would cause a short circuit and blow the fuse. We had a supply of extra fuses and easy access to the fuse box on the front dashboard, but by the end of the trip all we had left were 30 amp fuses. We may have left the wrong one in when we parked for the night. The fire caused excitement for a few minutes, but someone grabbed a cooler full of ice water to douse the flames. Pouring water on an electrical fire is perhaps not the wisest solution but it was effective and no one was electrocuted. The damage was limited to the dash and steering column, but of course the vehicle was not drivable. That resolved the problem for the night and we would take care of it the next morning. Tuesday, September 19th, Great Plains Physiographic Province (GPPP). After contemplating our predicament, we considered having the repairs done in Kansas, but that would have delayed the trip’s completion by at least a day. Jack Wunder remembers Dr. Larsen sitting alone on a park bench in the rest area looking understandably distraught, wondering how he was going to resolve the situation. Nonetheless, he persevered and arrived at a workable plan. It was the next to last day of our geologic odyssey and so to finish the long trek homeward Dr. Larsen decided to rent a tow bar after Ken Apple offered up his pickup truck for the approximately 850+ mile trek back to the UC campus. The five of us assigned to “Big Red” rode in it hoping that the tow bar never failed. If it did, the person in the driver’s seat would have to brake and steer to safety. Dalbey comments, after resolving our vehicle problem we drove eastward entering the Plains Border of the Central Lowlands of the GPPP, the largest geographic province in the U. S. over 585,000 square miles. The Central Lowlands occurs in ten north central states at elevations from 1,000 to 2,000 ft. asl. Kansas is roughly divided by the High Plains on the west and Central Lowlands in the east of the GPPP. We left the lower Cretaceous Dakota Sandstone and shales (non-marine) of the plateau (100-94 mya) that were deposited at the edge of a north to south trending marine sea between the Rocky mountains to the west and the continental plate on the east. Much of the High Plains bedrock exposures along I-70 east of Hays consists of relatively flat prairie over Cretaceous marine limestone, shales, mudstones and siltstones of the Smoky Hill Member of the Niobrara Formation. Erosion after 80 million years has created geologic features such as Castle Rock and other “hoodoo like” rock monuments within badlands topography in the Smoky Hills Region near Quinter, Kansas ca. 50 miles west of Hays, Kansas. The High Plains of Kansas once extended further east, but the east to southeast trending streams such as Saline, Solomon, Smoky Hill, Republican, Big Blue, Arkansas, Cimarron, North Canadian and Medicine Lodge rivers dissected and eroded higher less 68
residual bedrock. The erosion left bluffs of Niobrara Limestone, Smoky Hills Chalk, and Fort Hays Limestone exposed along their channels. The Middle Cretaceous marine, fossiliferous limestone of the Niobrara Formation (ca. 88-82 mya) overlies the Ft. Hays Limestone of the Smoky Hills throughout central Kansas. East of Ft. Hays, Kansas the Fort Hays Limestone Member underlies the Smoky Hills Member of the Plains Border Section and much of the larger Cretaceous Central Lowlands of the Great Plains. Almost the entire Cretaceous marine sequence is known for large marine fauna that include: plesiosaurs, pliosaurs, mosasaurs, huge Xiphactinus fish, sharks, ichthyosaurs, and large flying pterosaurs, to name a few. Ever since leaving Colorado we have been crossing the enormous GPPP with an area of ca. 1,200,000 sq. mi. from the Canadian provinces of Manitoba, Sascatchewan and Alberta on the north extending southward ca. 2,400 miles to the Texas coast. The GPPP stretches west to east over 500 miles consisting of Tall Grass (east), Mixed Grass (center), and Short Grass (west) prairie provinces, now reduced to less than 10 percent of the original extent. Tall Grass prairies consist of an enormous amount of biodiversity including the "Big Four" grasses: Big Bluestem, Little Bluestem, Switchgrass and Indiangrass that grow from 5 ft. to over 7 ft. tall, some reaching up to 9 ft. tall. Several stands of trees such as Oaks (Post, Blackjack), Hickories (creating savannas) and shorter trees occur along with numerous forbs numbering in the thousands. For example, sunflowers, rosinweed, gayfeathers, asters, coneflowers, milkweeds and so many more that bloom at different times most of the year and supported huge bird, insect, and animal populations. After crossing the confluence of the Saline and Smoky Hill rivers east of Salina, Kansas, we traveled east on I-70 towards Junction City we entered the north to south trending bedrock (Nebraska into Oklahoma) of the Flint Hills. Fifteen miles further east we crossed the Solomon River just north of the confluence with the Smoky Hill River south of the town of Solomon at I-70. Several large, south flowing creeks, glacial meltwater outlet channels meet the Smoky Hill River near the towns of Abilene and Chapman as we go east towards Junction City on I-70. We have now entered the valley of the ancestral Kansas River as the Smoky Hill River meets the broad valley (> 2.5 mi wide) of the glacial outlet valley where the Republican River flows south meeting the Smoky Hill River east of Junction City forming the current Kansas River at an elevation of just over 1,040 ft. asl. The confluence is ca. one mile west of the large Army base Fort Riley, in the Custer Hills (ca. 1,300 ft. asl) north of I-70 as the highway curves around the south part of the base. The “Flint Hills” are actually east facing cuestas known for Permian (ca. 280 mya) age chert that lies on the surface after weathering out from thin marine limestone deposits that cap hilltops. Elevations vary from 1,200 to 1,650 ft. asl to the south. The floodplain elevation of the Kansas River is ca. 1,000 ft.asl. The siliceous bedrock at or very close to the surface prevents agriculture but, increases grazing and preservation of natural prairies. The Permian “hills” occur in a north, ca. 65 mile wide expanse east of Salina to west of Topeka, tapering southward into northern most Oklahoma counties. The multicolored taupe to gray chert was sought after in prehistory for stone tool making by Native Americans. The Central Lowlands also represents the largest area of Tall Grass Prairie in the U.S. once 400,000 sq. mi., now reduced nearly 98 percent to a few preserves like the 17 sq. mi. Flint Hills Preserve. Several prairie preserves are located 69
in the Flint Hills eco-zone such as the National Tallgrass Prairie Preserve located about one hour south of Junction City as well as other small remnant prairies throughout the Flint Hills Province from Nebraska to Oklahoma. Except for perhaps, some rain forest areas in Brazil, the U.S. prairies support one of the highest biodiversity eco-regions on earth. Much of the northern land in the Central Lowlands has been glaciated many times over in the last two million years. There have been four major cold glacial periods and many warm interglacial intervals over this time period considered the Pleistocene that ended ca. 12,000 kya. The four major glaciations/interglaciations are known as: Nebraskan/Aftonian the oldest (ca. 1.0 - 2.0 mya), Kansan/Yarmouth (1.0 - 0.5 mya), Illinoian/Sangoman. (0.5 - 0.13 mya), Wisconsin/Holocene (0.13 - 0.012 mya). Early Pre-Illinoian glacial (Nebraskan and Kansan) lobes reached into the northeast corner of Kansas ca. 75 miles south from where the Illinois state line is now located and extended south to where Topeka and the I-70 corridor are now located. The present Kansas River Valley was mostly formed by the Kansan glaciofluvial outwash from the glacier and terminus deposits that form high alluvial banks along the river up to 200 feet high. From Junction City, I-70 goes straight east ca. 65 miles to Topeka. However, from Junction City, the Kansas River deviates about ten miles in an old river channel northern arc from I-70 to Manhattan, Kansas 20 miles east of Junction City. East of Junction City we crossed the Smoky Hill River as we passed the confluence of the Republican River that flows from the northwest through dissected till plains to the Smoky Hill River from the southwest. These rivers combine with the waters of the Saline and Solomon rivers that capture the drainage of the Republican River flowing from the north to form the Kansas River that has been rejuvenated in the older pre-glacial to Kansan glacial, ca. 2.5 miles wide, ca 130 miles long river valley. The east flowing Kansas River follows the southern limit of Pre-Illinoian glaciation where the southwestern lobe of earlier glaciers (Nebraskan and Kansan) deposited displaced erratics and glacial drift from the Canadian Shield on the till plain. The erratics (nonlocal bedrock from a distance) range in size from cobbles and boulders, to house size, and occur in an arc from Barneston, Nebraska near the Kansas border in the north to the south flowing Big Blue River catchment east of Manhattan. The Big Blue River is the largest Kansas River tributary that flows through the northern dissected till plains southward eroding previous glacial outwash into the Kansas River. The river was a direct glacial outwash channel where large glacial erratics were deposited on the till plains after the glaciers melted. The glacial erratic field continues 15 miles east to Wamego where we crossed the Vermilion River another glacial outwash stream that flows into the Kansas River in a four mile wide river valley. Ten miles north of I-70, east of Topeka (ca. 35 mi.). many glacial erratics that were incorporated in the glaciers were deposited in terminal moraines and left behind when the glaciers melted, also known as “dropstones,” or fields of ice rafted debris. The large erratics consist of quartzite, granite, diamictites (Gowgandan formation, Paleoproterozoic Huronian Supergroup), quartz conglomerates, agates, iron ore, volcanics, copper and catlinite (aka. pipestone) that originated from as far north as over 400-1,000+ miles. As we went further to Topeka, Kansas we were 70
within the ancestral Kansas River Valley, and then again, the channel deviated south at the confluence of the Delaware River east of Topeka. At the height of glaciation tundra arctic conditions prevailed as glaciers advanced and melted with varying environmental conditions. The colder climate created steppe conditions with grasslands, few trees poplar and aspen forests alternating with spruce, fir, and pine taiga environments. Closer to the glaciers tundra conditions prevailed with little vegetation until the glaciers melted. They left behind in their wake dissected till plains of varying depth covered with loess (one foot to 300 ft.), grasslands, moraines, kames, eskers, drumlins and kettle lakes across the plains. The east flowing Wakarusa River south of Topeka flows west to east through the glacial drift of the Kansan glacier to Lawrence where it meets the Kansas River 35 miles west of Kansas City, Kansas. Numerous kettle lakes occur from where blocks of glacial ice melted in place were often associated with kame fields across the once glaciated landscape. There were numerous creeks flowing from the north into the Kansas River channel. From Lawrence, the present Kansas River course flows roughly parallel to I-70 for the last 40 miles to the confluence with the Missouri River on the north side of the city. Cumulatively, all the drainages of all rivers we crossed east of the Solomon River to the Missouri River at Kansas City were influenced by the melting of northern glaciers that were greater than one mile thick to the north. The southern outflow of glacial waters carrying glacial outwash filled the channels with sediments to ca. 100 feet deep in some places. On the west side of Kansas City, the Kansas River flows through loess hills as it flows north to the Missouri River where loess deposits reach over 200 feet high at the confluence where the state line between Kansas and Missouri is located. In the Kansas City area outcrops can be seen of Paleozoic swampy shaley bedrock (laminated coal) from Late Pennsylvanian seas that transgressed onto land and regressed to shallow seas. These are conformably overlain by Permian limestones of shallow marine bedrock age 270-300 mya. Millions of years later prior to northern continental glaciation all the rivers in northern Missouri, the Dakotas, east Montana and Minnesota flowed north. The Pleistocene glaciers reversed the flow of rivers, filling paleo-channels with alluvium, leveled and planed the topography of an area that was once on the coast of Gondwana. Paleozoic bedrock bluffs are covered by wind blown loess up to depths of 200 ft. along the rivers while the same bedrock in the Missouri River channel is filled with 100-150 ft. of alluvium derived from glacial outwash. We mostly bypassed Kansas City but we could see the high bluffs along the river covered with glacial deposits and several limestone outcrops with several faults as we were headed east towards Columbia, Missouri where we were going to spend the night of September 19th. We crossed the Missouri River Valley again as we headed east on I-70 before we got to Columbia, Missouri. The Missouri river is the longest in the U.S. The section we are following runs north of I-70 roughly paralleling the river to Columbia where the river course turns southeastward all the way to St. Louis. Interstate 70 crosses more of the Central Dissected Till Plains that we saw in Kansas where the Pleistocene glaciers leveled much of the topography. Most of the hills and valleys of the dissected till plains were filled in and covered with savannah and grass lands still in the Central Lowlands of the GPPP. In about 10 hours we travelled ca. 400 miles from 71
Hays, Kansas to Columbia, Missouri on Tuesday, September 19th with “Big Red” in tow. Wednesday, September 20th, after spending the night outside Columbia, Missouri we traveled east on I-70 ca. 142 miles, for 2.5 hours to get to St. Louis with Big Red still in tow. Along I-70 from Columbia going through Missouri we passed terminal moraines of Illinoian glaciation, karst topography and flat drift topography. We were traveling across more of dissected till plains on I-70, but as we got closer to St. Louis we observed outcrops of the Ordovician. The geologic structure of the area is on the northern periphery of the Ozark Uplift bordered by the Missouri River starting east from Jefferson City, Missouri to St. Louis. The igneous uplift intrusives date to ca. 1.5 bya representing a domal feature that eroded for ca. 1.25 bya into an off shore Laurentia marine basin that was uplifted during the Carboniferous Ouachita Orogeny creating in part the Ozark Paleozoic sedimentary plateau that has been eroding ever since. The uplift is centered to the southeast in the Saint Francois Mountains created during Precambrian igneous mountain orogenic activity. At St. Louis we crossed the confluence of the Mississippi and the Missouri rivers. St. Louis is at the confluence of numerous major river corridors that come together within ca. 100 miles as a result of glaciation, geology, physiography and topography, from north to south: Mississippi, Illinois, Missouri, Meramec and Kaskaskia forming one of the largest riverine corridors in the world. From St. Louis to Cincinnati we back tracked over the same route we took when we left Cincinnati for the southwest so the geology we traveled was the same. See the geology descriptions at the beginning of the report that cover Cincinnati to Albuquerque. We pulled into the UC parking lot about 3 PM ending a fantastic 20 day field trip. CONCLUSION The trip was a tremendous success for all of us. We saw amazing natural places and very interesting geological phenomena, and learned a whole lot of geology. We functioned as a coordinated group and enjoyed what could be called a two week working vacation. Friendships were seeded that grew and developed into life-long relationships. All sixteen members of this tribe of budding geologists felt a deep gratitude toward this kind and knowledgeable man who gave freely of his time to share his experience in the science of geology that he loved so dearly. He gifted us with memories that have lasted a lifetime. But perhaps the summary of the trip is best expressed in the words of Dr. Larsen himself. To the trip participants: “The trip stands in my memory as enjoyable and successful. I particularly enjoyed the good fellowship. As a group and individually I enjoyed being with
72
you, and I want to thank you for your cooperation and enthusiasm. It really made the trip outstanding for me.” Leonard Larsen, October 3, 1972. “P.S. A refund of $3.10 is due some of you. I will send it in the mail sometime soon.”
New Mexico portion of the trip.
73
Arizona portion of the trip.
74
Utah portion of trip.
Colorado portion of trip.
75