What are these rocks telling us?

“The heart of field geology is going up to rocks and getting them to tell you their stories” (source).

Beneath us are hundreds of feet of rock, often in layers that can be read like chapters in a book … if only we could see them! Fortunately, rivers sometimes come to our aid, cutting down through rocks to reveal their stories. Probably the most famous is the masterpiece cut by the Colorado River—the Grand Canyon. This is a story 1.75 billion years long, told in a stack of rocks a mile thick. The tale is fairly straightforward; sediments were turned to rock but otherwise not much altered. They remain mostly flat, like an immense layer cake.

Panorama from Point Sublime. WH Holmes, 1882. David Rumsey Map Collection.

But sometimes the reading isn’t so easy. Consider the cuts made by the Yampa and the Green, near their confluence on the south flank of the Uinta Mountains. I spent a long time pondering them, and never really understood the whole story. But I didn’t mind—it was a beautiful and remarkable place to be.

“Like an expression of frozen movement, or of time standing still, these faults accent the grandeur of the scene and stir wonder in the heart of the viewer.” Wallace Hansen, 1969

Confluence of Yampa and Green Rivers. View from Harpers Corner Trail, Dinosaur National Monument.

First I had to figure out which river was which. Fortunately I had help—the Harpers Corner Trail Guide (river labels circled: yellow – Yampa, green – Green).

The Green River flows south behind a long sandstone fin, is joined by the Yampa, and then turns back sharply to the north. In the photo below, the dashed arrow is the Green behind the long sandstone fin.

A Google Earth view helps:

These are crazy rivers!

The Yampa and the Green are thought to be superimposed drainages. There was a time when the Uinta Mountains were nearly buried in their own debris—sediments eroded off the range—and the Yampa and the Green flowed across the thick layer of debris as broad meandering streams. But then the region was uplifted, and erosion exhumed the buried mountains. The meandering rivers were “lowered” onto the underlying rocks, but they kept cutting down and maintained their circuitous paths! The Yampa is especially sinuous, winding for 22 miles through narrow canyons to cover less than ten air miles before joining the Green. [The whole story is more complicated; see Hansen 1986).]

Looking east up the Yampa River, above the confluence with the Green.

After making the sharp bend back north, the Green heads west and crosses the Mitten Park Fault, which it has exposed spectacularly for all to enjoy.

“Few faults anywhere are better displayed” (Hansen 1969). USGS photo, 1959.

These rocks started as sediments laid down on beaches, shallow sea floors, and in deltas and swamps, layer after layer. Next came humongous fields of sand dunes, and so on … for millions of years. The sediments were lithified, becoming a stack of mostly flat rock layers.

So why are they no longer flat? In fact, why are these rocks so severely deformed?! It's because they got caught up in mountain-building—specifically uplift of the Uinta Mountains between 70 and 40 million years ago.

Mitten Park Fault, NPS photo.

The folded rocks and fault were clear, especially with the trail guide to help, but the story behind them was not. This is not an easy read! The steeply-tilted rocks may be part of the local monocline—the huge step-like fold visible to the east. It’s broken by the Mitten Park Fault, with rocks to the east down-dropped relative to those to the west. Perhaps they were drug along the fault as the blocks moved past each other, creating the spectacular folds or enhancing those already there.

Monocline arrow marks change in dip from steep to gently-sloping.

Rocks left (west) of the fault are older and still roughly horizontal. Those at the same level to the right (east) are younger and severely deformed.

The timing is unclear. Some sources suggest the Mitten Park Fault came to be during the main uplift of the Uinta Mountains. Or it may represent a later stage, when the crest of the eastern Uintas collapsed (wow!). Movement may continue into the present.

In any case, these folded faulted rocks lay deep underground until the Green and Yampa Rivers finally cut down far enough to expose them.

Contrary to appearances, it wasn't a cataclysm that produced these tortuous rocks—just slow steady work. Crustal plates shifted a bit, rocks gradually folded, fractures grew inch by inch, maybe there was an occasional earthquake. This went on for tens of millions of years. Then the rivers went to work, slowly excavating dirt and debris, eventually exposing the rocks. But even with a plot this monotonous, a story tens of millions of years long can have a dramatic climax.

Having added a tiny bit of dirt from Mitten Park to its load, the Green continues on (NPS).

This is the last post from my September trip to the Uinta Mountains—a place I had long wanted to visit (~30 years) and finally did. Two weeks were only enough for an introduction; I need to return. Many thanks to Mike of CSMS GEOLOGY POST for the encouragement, and for recommending books to read, places to go, things to see.

Sources

Frishman, JA. 2011. Crest, Cliff and Canyon (blog), Geology of Dinosaur National Monument.

Gregson, JD, and Chure, DJ. 2000. Geology and paleontology of Dinosaur National Monument, Utah-Colorado: in Sprinkel, DA, Chidsey, TC, Jr. and Anderson, PB, eds. Geology of Utah’s Parks and Monuments. Salt Lake City: UGA Publication 28, p.155-188.

Hansen, W. 1969. The geologic story of the Uinta Mountains. USGS Bulletin 1291. PDF

Hansen, W. 1986. Neogene tectonics and geomorphology of the eastern Uinta Mountains in Utah, Colorado, and Wyoming: USGS Professional Paper 1356.

Untermann, GE, and Untermann, BR. 1969. Popular guide to the geology of Dinosaur National Monument. Dinosaur Nature Association. (out of print)

A Pioneering Geologist on Uinta Plants

Linosyris?

Required reading for my recent trip to the Uinta Mountains included several reports from early exploratory expeditions. The Uintas are rich in this kind of literature—the great pioneering geologists Ferdinand Vandeveer Hayden, Frank Emmons (working for Clarence King), and John Wesley Powell all passed through in the decade after the American Civil War. Their writing is scientific and filled with detail. But it's not boring, infused as it is with the excitement of discovery. Passing through the same landscapes, camping by the same rivers, pondering the same outcrops, I feel some of that excitement myself.

Though these men were geologists, they didn’t ignore plants. Usually they had a botanist along, or at least someone capable of collecting and preparing specimens. Those specimens that survived the rigors of travel were sent to experts, who studied and identified them, perhaps describing much-coveted “novelties”—species new to science. A plant list was included in the final report. The leaders themselves recognized the more common plants, and they often described the vegetation of the areas they passed through, in addition to geology, wildlife, natural resources, and any people they encountered.

In September of 1870, Ferdinand Vandeveer Hayden led his US Geological and Geographical Survey of the Territories into Brown’s Hole—the broad valley of the Green River in the eastern Uinta Mountains (now Browns Park):

“There is but little timber along the immediate valley of Green River—only a few bitter cottonwoods and willows; but on the hills there is a thick growth of the low piñon and cedars. … in the valley, there is a universal growth of the sage, (Artemisia tridentata,) greasewood, (Sarcobatus vermicularis, ) and Linosyris.”

When I visited Browns Park 146 years later, also in September, I found the vegetation much the same. There were occasional stands of bitter cottonwoods (today’s narrowleaf and lanceleaf) along the Green River, and pinyons and “cedars” (junipers) covered the hills. In the valley bottom, sagebrush and greasewood were extremely common. But Linosyris? I had never heard of this “universal growth” plant. Yet there was nothing common I didn’t recognize. Did geologist Hayden really know what he was talking about? Was Linosyris a misidentification?

A google search revealed that Linosyris grows in Asia, Europe and Great Britain. There are no species native to North America. But when I looked at images, I realized Hayden probably was correct … probably he was just another victim of nomenclatural change.

According to Google, the three plants below are called "linosyris." What very common plant of the basins of the American West do you think Hayden saw? [1. Type specimen of Linosyris (Aster) grimmii from Turkestan, Muséum National d'Histoire Naturelle; 2. Galleta linosyris (“goldilocks”); 3. Linosyris villosa, Russia, maybe today's Aster oleifolius.]

As botany students, we’re repeatedly assured that scientific (Latin) names avoid the horrendous ambiguity of common names. But then when we go out into the real world, we quickly learn that these names change too, as taxonomists study and reclassify plants. To make things worse, experts don’t always agree. Old literature is especially challenging.

But Hayden’s Linosyris puzzle was easy to solve. In the “Catalogue of Plants” at the end of the report was Linosyris graveolens, under Compositae (Aster family). graveolens and compositae were the final clues. This is our rubber rabbitbrush, Ericameria nauseosa var. graveolens, which used to be a member of the genus Linosyris.

Rabbitbrush is extremely common in Browns Park. It definitely qualifies as “universal growth”—especially in September when it’s covered in flowers.

Bright golden floral displays can’t be missed.

Rubber rabbitbrush in morning sun.

Stems have a felt-like covering of dense white hairs.

As you may have guessed, rabbits like rabbitbrush. In fact, many wildlife species benefit from its abundance. Birds and small mammals use it for cover. Deer, antelope, elk, small mammals and birds feed on the leaves, flowers and seeds. Rabbitbrush is visited by a wide range of native insects, especially in late summer and fall. It’s said to support more native bee pollinators than any other cold desert shrub in the Intermountain West (Waring 2011).

Typical of the Aster family, what look like rabbitbrush flowers aren’t flowers. They’re small heads of tiny flowers, each with reproductive parts—stamens and pistils. [The Aster family was originally called Compositae because what look like flowers are actually composites. Not that long ago, it was changed to Asteraceae to be consistent with naming rules.]

The pungent flowers explain the scientific name, Ericameria nauseosa. But they're not that bad. I would say resinous rather than nauseating.

Flowers are tubular, less than a half inch long. Stamens and pistils emerge from the tubes. Source.

I took many photos of rabbitbrush in Browns Park … unintentionally. It was that common.

With dark dikes intruded into the ancient Red Creek Quartzite (more here).

With more rocks from the core of the long-gone Red Creek mountain range.

On a CO2 pipeline project (more here).

Approaching the Gates of Lodore on the Green River.

Rabbitbrush lined most of the roads in Browns Park, which isn't surprising since it thrives on disturbed sites. It often dominates initially, but in the absence of continued disturbance, becomes just a minor part of the native vegetation.

Above and below: rubber rabbitbrush along the Irish Canyon road, which cuts through the north flank of the Uinta Mountains near the east end of Browns Park.

Rabbitbrush is taking over the dugout where James Jarvie lived in 1880, his first year in Brown’s Hole.

In between Linosyris graveolens and Ericameria nauseosa, rubber rabbitbrush was called Chrysothamnus nauseosa. This is my choice of names because Chrysothamnus means “golden shrub”—which they certainly are! Rabbitbrushes are super difficult to classify, and experts surely will continue to rename them. Maybe someday some taxonomist will move rubber rabbitbrush back into Chrysothamnus, proving me prescient ;-)

Rubber rabbitbrush is the most complex of the rabbitbrushes, with 24 subspecies and varieties, many of which overlap or hybridize. Within these, there are multiple ecotypes, for example adapted to different soils. And within ecotypes there’s a “great deal of variability in morphological characteristics and chemical composition” (Scheinost and Ogle 2010). No wonder rubber rabbitbrush is so successful—so widespread and common. And no wonder rabbitbrush taxonomists struggle to classify them. In this case, maybe it’s best to use common names after all.

Rubber rabbitbrush and rainbow on my last day in Browns Park.

Sources

Anderson, L. 1995. The Chrysothamnus-Ericameria connection (Asteraceae). The Great Basin Naturalist, 55:84-88. Retrieved from http://www.jstor.org/stable/41712868

Porter, TC. 1871. Catalog of plants. in Hayden, FV. Preliminary report of the United State Geological Survey of Wyoming, and portions of contiguous territories. Washington: Government Printing Office. [Thomas C. Porter was professor of botany, geology and zoology at Lafayette College in Easton, Pennsylvania.]

Scheinost, PL, Scianna, J, and Ogle, DG. 2010. Plant guide for rubber rabbitbrush (Ericameria nauseosa). USDA-Natural Resources Conservation Service, Pullman Plant Materials Center, Pullman, WA. https://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs144p2_042451.pdf. Accessed 2016, November 29.

Tirmenstein, D. 1999. Ericameria nauseosa. In: Fire Effects Information System [Online]. USDA Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory. Nomenclature updated 2014. http://www.fs.fed.us/database/feis/. Accessed 2016, November 29.

Waring, GL. 2011. A natural history of the Intermountain West; its ecological and evolutionary story. University of Utah Press.

About that pipeline in Jesse Ewing Canyon …

Sequestration?

Near the end of my recent post about a geo-hike down Jesse Ewing Canyon in the eastern Uinta Mountains, I mentioned a pipeline. There was no way to miss it—it was clearly and emphatically marked.

Pipeline route down Jesse Ewing Canyon into Browns Park. Uinta Mountains continue in the distance.

Why is CO2 sent down Jesse Ewing Canyon, across Browns Park, over the Green River and up into the Uinta Mountains? In fact, why is carbon dioxide being transported at all?

CO2 crosses the Green in a pipeline suspended above the river.

Arrow marks pipeline route above Browns Park, after crossing the Green River.

My first thought was sequestration. Oil and gas extraction produces climate-warming CO2, and the industry is under pressure not to release it into the atmosphere. In Wyoming, we talk a lot about carbon capture and sequestration (CCS) … could this CO2 be going somewhere in the Uintas to be injected into suitable rock layers deep underground? Of course that would require Federal funding—sequestration is expensive!

Or could it be that this CO2 is being somehow put to use? That’s what I asked a candidate for the Wyoming state senate, a passionate advocate for research on economically-viable uses of CO2. But like me, he was puzzled and guessed Federally-subsidized sequestration. But we were wrong. The CO2 is being put to use, specifically for enhanced oil recovery (EOR). It's sent to an aging oil field to extract a bit more oil.

The CO2 originates at the LaBarge natural gas field in southwest Wyoming. After being captured and processed, it travels southeast to Rock Springs, then south through Clay Basin to the head of Jesse Ewing Canyon in Utah. Next it descends to Browns Park, crosses the Green River, climbs a bit higher into the Uintas, descends, crosses the Green River again, and finally arrives at Rangely, Colorado, after a trip of 177 miles.

Bold line is the Rangely pipeline route (BLM 1984).

At Rangely, CO2 is injected 6000+ feet underground into the Weber Sandstone. The Weber was once dunes and river sand, back during the time of the Ancestral Rocky Mountains 245-315 million years ago. Several hundred million years later, after the sand had turned to rock, the Laramide Orogeny (uplift of the modern Rocky Mountains) folded the rocks to produce the Rangely Anticline—an elongate dome with multiple layers of trapped oil.

The Rangely field is one of the largest in the US, “with cumulative production of about 900 million barrels of oil and 700 billion cubic feet of natural gas” (as of 2014; source). Serious production began in 1933 and peaked around 1955. Since then, secondary (water) and tertiary (CO2) enhanced oil recovery have been used to coax more oil out of the ground.

CO2 enhanced oil recovery started at Rangely in 1986. It didn’t reverse production trends longterm—the Rangely is mature and most of the oil is gone. But there was a shortterm increase, enough to justify expenditures.

Originally from Chevron; found on multiple websites (see Sources).

Earlier, I hinted that extra financial incentives drive carbon sequestration … is that true for enhanced oil recovery as well? Is it really profitable to buy processed CO2 and ship it 177 miles? The Shute Creek (LaBarge) processing plant alone cost $70 million to build, and as of 2005, required $1 million per month to operate (CO School of Mines 2005). Not surprisingly, EOR is a balancing act strongly influenced by market forces.

“Enhanced oil recovery processes reverse the trend toward lower oil cuts for a short term, but even these processes become victims of dropping oil cuts. When this happens in a tertiary CO2 miscible project, the added burden of CO2 purchase and recycle costs makes competing with lower cost oil difficult. This increases the risk for early abandonment of once proved EOR reserves and a lower financial yield on the sizable EOR investments.” (Masoner and Wackowski 1994)

As of late 2015, CO2 was still traveling the 177 miles from LaBarge to Rangely (Smith 2016), suggesting EOR was still profitable.

Because so much CO2 has been injected into the Weber Sandstone (26 million tons as of 2010), Rangely is being counted as a carbon capture and sequestration project (IEA 2010). So the senate candidate and I were partially right in guessing sequestration … or were we? Maybe not. Enhanced oil recovery may well generate more CO2 than it sequesters! See Thomas W. Overton’s recent discussion in Power Magazine (April 2016):

“From where I’m sitting, if the point of CCUS is to reduce CO2 emissions, EOR is about the last thing it should be used for. On the other hand, if the point is to redistribute vast amounts of money, it’s off to an excellent start.”

Our CO2 pipelines (Wallace et al. 2015).

Sources

Biello, D. 2009. Enhanced oil recovery: how to make money from carbon capture and storage today. Scientific American (online). https://www.scientificamerican.com/article/enhanced-oil-recovery/#

Bureau of Land Management. 1984. Rangely carbon dioxide pipeline; public scoping document. https://ia601602.us.archive.org/4/items/rangelycarbondio05unit/rangelycarbondio05unit.pdf

Colorado School of Mines. 2005. ChevronTexaco’s Rangely oil field operations. http://emfi.mines.edu/emfi2005/ChevronTexaco.pdf

Cramer, R. 2014. Vertical conformance, the challenge at Rangely. http://www.co2conference.net/wp-content/uploads/2014/12/9-Cramer-Chevron-Conformance_Improvement_The_Challenge_at_Rangely_12-11-14.pdf

Gibson, R. 2014 (July 8). Rangely oil & gas field. History of the Earth (blog). http://historyoftheearthcalendar.blogspot.com/2014/07/july-8-rangely-oil-gas-field.html

International Energy Commission. 2010. Report to the Muskoka 2010 G8 Summit: carbon capture and storage; progress and next steps. http://www.ccsassociation.org/docs/2010/IEA%20&%20CSLF%20Report%20to%20Muskoka%20G8%20Summit.pdf

Masoner, LO, and Wackowski, RK. 1994. Rangely Weber sand unit CO2 project update: decisions and issues facing a maturing EOR project. Society for Petroleum Engineers. http://dx.doi.org/10.2118/27756-MS

Overton, T. 2016. Is EOR a dead end for carbon capture and storage? Power Magazine (online). http://www.powermag.com/is-eor-a-dead-end-for-carbon-capture/

Reitenbach, G. 2016. When technology tails wag power dogs. Power Magazine (online). http://www.powermag.com/technology-tails-wag-power-dogs/

Smith, T. 2016. Teamwork at Rangely. Geoexpro 12:74-77. http://www.geoexpro.com/articles/2016/01/teamwork-at-rangely

Wallace, M. et al. 2015. A review of the CO2 pipeline infrastructure in the US. US DOE. http://energy.gov/sites/prod/files/2015/04/f22/QER%20Analysis%20-%20A%20Review%20of%20the%20CO2%20Pipeline%20Infrastructure%20in%20the%20U.S_0.pdf

Surprise Geo-hike in the Eastern Uinta Mountains

Jesse Ewing Canyon down to Browns Park; highly recommended!

I knew there was a problem when I saw a sign warning of a 14% grade—it should have been 17%. And there was pavement where there should have been gravel. The road had changed. The drop in grade meant it was longer and mileages in the guidebook no longer applied. How would I know what I was looking at?! Even worse, the new road might bypass the ancient rocks of Jesse Ewing Canyon altogether.

But my fears were unfounded. The Browns Park Road had indeed been rerouted, but as a result, Jesse Ewing Canyon is now a great geo-hike. Instead of trying to pull off a steep narrow road, we strolled down the canyon, stopping to ponder the remains of the ancient Red Creek mountain range, a substantial unconformity, and the magnificent conglomerate at the base of the Uinta Mountain Group.

The Uinta Mountains are part of the Rocky Mountains, having been uplifted during the Laramide Orogeny around 70-40 million years ago. The western half is known as the High Uintas—there are 26 peaks 13,000+ feet in elevation, including the high point of Utah, Kings Peak. Pleistocene glacial features are common. Late Precambrian sandstones and quartzites dominate the high country.

Uinta Mountains (from Atwood 1909, labels added).

The eastern Uintas are different. They max out at only 9710 feet (Diamond Peak), were not glaciated, and are more complex structurally. And Precambrian rocks are older—in a few places much older, for example in Jesse Ewing Canyon.

I drove up the new paved road on a giant switchback, which explained the reduction in grade. Several road cuts displayed contorted multi-colored rocks, but there was no place to stop. At the top of the climb, I parked in a gravel pullout which turned out to be the old road, now closed. This was the start of the Jesse Ewing Canyon Geo-hike.

Start of geo-hike. Browns Park and more of the Uinta Mountains in the distance.

Less than a quarter mile down the old road were the rocks I was looking for—a mix of quartzitic and schistose rocks of the Precambrian Red Creek Quartzite. The outcrops are modest, but their story is impressive—mind-boggling actually. These are the remains of mountains that disappeared in the far distant past. A billion years ago, they had been eroded nearly flat; 500 million years later they were buried deep in debris. Tens of millions of years ago, faulting and erosion exposed them, but only in this part of the Uintas.

Early geologists were puzzled as to why these rocks occur only here.

From 1868 through 1871, the Uinta Mountains were crawling with geologists … ok, there were only three, but they all were key figures in the geological exploration of the western US: John Wesley Powell, Frank Emmons (working for Clarence King), and Ferdinand Vandeveer Hayden. Why did the US government fund three nearly simultaneous expeditions into the Uintas? Maybe it was because of the spectacular geology. Or maybe these men had powerful connections in Washington DC.

Great geologists though they were, they found the Precambrian rocks of the Uinta Mountains puzzling. Ironically, it was Hayden—a physician with no formal training in geology, and looked down upon for his too-cursory surveys—who came up with the most modern explanation: [“white quartz” is Red Creek Quartzite; “red quartzites” are rocks of the Uinta Mountain Group]

“I find it difficult to account for this tremendous development of quartz[ite] with gneiss at the eastern end of the Uinta range. The white quartz[ite] beds rise abruptly from beneath the red quartzites, occupying a belt five to nine miles in width, and end as abruptly as they commence. I do not know why they should appear at this locality, when further to the west, at the sources of Black's Fork and Bear River, where the rocks rise to an elevation of over 13,000 feet, no trace of them can be seen … I am inclined to believe that the immense thickness of quartz[ite] was thrust up beneath the red quartzites, carrying the latter so high up that they have been swept away by erosion, except the remnant now remaining.”

 Just a half page later, Hayden revealed his naiveté:

“The geology of this portion of the Uinta range is very complicated and interesting. To have solved the problem to my entire satisfaction would have required a week or two [italics added].”

A bit further down the canyon, the Red Creek Quartzite gave way to younger rocks. As usual, I had to pause to clear the confusion in my head. In an undeformed series of rocks, the youngest layer is on top and the oldest at the bottom; in other words, a rock layer is younger than the one below and older than the one above. So whenever I make a counterintuitive descent through progressively younger rocks, as we often do in the Rockies, I have to draw a picture in my head explaining why. It’s because the rock layers were tilted when the mountains were uplifted …

Orderly rocks, following Steno’s Law of Superposition.

Same rocks, after uplift (tilting) and erosion.

… ok, now we can keep going.

Darker rocks beyond the Red Creek Quartzite are much younger, but still Precambrian.

Atop the Red Creek Quartzite (but down the road) lie basal rocks of the Uinta Mountain Group (UMG). Like Red Creek rocks, the UMG dates from the Precambrian. But to leave it at that—and thereby suggest proximity in time—would be misleading. The Precambrian is an immense span. It includes the first four billion years of Earth history—out of 4.6 billion total! Geologists used to relegate this distant mysterious time to one gigantic eon, but now the various episodes are being teased apart, and the Precambrian has become a subdivided Supereon.

Geologic clock showing Red Creek Quartzite and much younger UMG (source; labels added).

The Red Creek Quartzite has been dated at 2.3 billion years, which places it in the Paleoproterozoic Era. It may be even older—latest Archean. In any case, it formed roughly mid-Precambrian. In contrast, the UMG is only 850 to 720 million years old, from the mid-Neoproterozoic—not all that long before the Precambrian Supereon came to an end. Between the Red Creek Quartzite and UMG is a major unconformity—a gap in the rock record of almost 1.5 billion years.

This draw marks a 1.5-year gap in the record. Feels like a Great Unconformity to me!

UMG rocks started out as sediments washed into in a continental rift, perhaps when the supercontinent Rodinia was coming apart. This went on for 100+ million years; the resulting accumulation may be as much as 25,000 feet thick! Rocks range from sedimentary—mainly sandstone with some siltstone and conglomerate—to metasedimentary and metamorphic—mainly quartzite of various grades.

Like the Red Creek Quartzite, the oldest (basal) rocks of the UMG crop out only in the eastern Uintas. They are beautifully exposed in Jesse Ewing Canyon—large pale quartzite clasts are set in a dark red to maroon matrix. The first debris to wash into the developing continental rift was dominated by large angular fragments from the Red Creek mountain range. Size and shape indicate they didn’t travel far.

The distinctive conglomerate has been designated the Jesse Ewing Canyon Formation.

Conglomerate, with virgin's bower (Clematis).

The conglomerate itself has been fragmented. Here's a piece in the old roadbed.

Down the road, the conglomerate gave way to younger finer-grained rocks, mainly reddish-purple sandstones. They continued to the lower end of the canyon—all part of the UMG.

Like the Red Creek Quartzite, the UMG fooled the great geologists. None of them assigned it to Precambrian time; they all thought it was younger. Thirty-five years after his pioneering work, Frank Emmons returned to the Uintas, at age 65. This time he concluded that the UMG was Precambrian. He didn’t apologize for his earlier error. Instead, he prefaced his presentation to the Geological Society of America with this timeless explanation:

“A generation has passed away since these maps were made, during which time the advance in geological knowledge of the West has been so great and the change in methods of work so radical that it is difficult for the younger generation of geologists to appreciate the conditions under which geological work was then done.” (Frank Emmons, 1907)

At the lower end of the canyon, the UMG suddenly disappeared at a fault bordering Browns Park, the broad valley of the Green River. Suddenly we were strolling among Tertiary rocks—fine sediments and volcanic ash that filled the valley just 10-20 million years ago. Since then, erosion has set the debris moving once again … down the Green to the Colorado River and points beyond.

Pale outcrops against dark red slope behind mark Browns Park fault. Boulders are Jesse Ewing Canyon conglomerate.

Fittingly, Jesse Ewing Canyon memorializes a geologist … of sorts. Prospector Jesse Ewing lived in a cabin near the head of the canyon. He had a bad reputation, with at least one murder to his name. He himself was murdered in 1885, “ambushed by Frank Duncan in dispute over the affections of Madam Forrestal,” a former resident of the Rock Springs red-light district. Ewing was buried at the Jarvie Ranch by John Jarvie and Albert Speck Williams. Twenty-four years later, Jarvie was murdered, by drifters from Rock Springs. Far from civilization, Browns Park was a rough place to live (more here).

Directions

Start the Jesse Ewing Canyon Geo-hike from either the top or bottom of the canyon (do you prefer to go forward or back in time?). Or maybe do a loop if you want to look at cuts along the paved road—it’s not heavily-traveled.

Top of canyon: 40°56'8.23"N, 109° 8’45.74"W

Numbered signs mark a pipeline route. Note Paleoproterozoic road cut right of center.

Bottom of canyon: 40°54'49.72"N, 109° 8'44.91"W

Another view of the Browns Park fault. New road visible on left.

Sources (in addition to links in post)

Aalto, KA. 2005. Pioneering geologic studies of the Uinta Mountains by the great post-Civil War surveys of King, Hayden and Powell, in Dehler, CM, Pederson, JL, Sprinkel, DA, and Kowallis, BJ, eds. 2005. Uinta Mountain geology. Utah Geological Association Publication 33.

Atwood, WW. 1909. Glaciation of the Uinta and Wasatch Mountains. USGS Prof. Paper 61.

Dehler, CM, and Sprinkel, DA. 2005. Revised stratigraphy and correlation of the Neoproterozoic Uinta Mountain Group, in Dehler, CM, Pederson, JL, Sprinkel, DA, and Kowallis, BJ, eds. 2005. Uinta Mountain geology. Utah Geological Association Publication 33.

Emmons, SF. 1907. Uinta Mountains. Geological Society of America Bulletin. 18:287-302.

Hansen, W. 1969. The geologic story of the Uinta Mountains. US Geological Survey Bulletin 1291. PDF

Hayden, FV. 1871. Preliminary report of the United State Geological Survey of Wyoming, and portions of contiguous territories. Washington: Government Printing Office.

Tennent, WL. 1981. John Jarvie of Brown’s Park. Bureau of Land Management - Utah; Cultural Resources Series No. 7. Available here.