Monday, April 21, 2014

Across the West and Back Day 2: Beyond the Wasatch

It was a cloudy and soon to be stormy day, and we were just about over the Wasatch, just about to U.S. 189, which runs in a northeasterly direction through Provo Canyon toward Heber City, where we planned to meet up with U.S. 40. On our way to 189, still on S.R. 92, we passed by one or two roadcuts exposing some tilted beds, a general configuration that was rapidly becoming familiar on our trip, one I soon came to think of as "another tilted section." In this case, it turned out that we were looking at the basal member of the Oquirrh Formation: the Bridal Veil Limestone.
Bridal Veil Limestone member of the Oquirrh Formation, Pennslyvanian in age.
I found out later—from Geolex—that this medium to dark gray, thick to thin bedded limestone, which was named for Bridal Veil Falls on the south side of Provo Canyon, is about 1200 ft thick.

We made it into Provo Canyon. About 3 miles up the canyon, Highway 189 crossed from the north side of the canyon to the south side, ending up south of the dammed Provo River at Deer Creek Reservoir.

We started seeing some modified roadcuts.
A modified roadcut of the Bear Canyon member of the  Oquirrh Formation.
These types of roadcuts, where the steep rock exposures appear to be cemented for slope stabilization and then painted or stained to look somewhat like natural rock, became another hallmark of our trip, being seen fairly commonly at least in Utah and Colorado. I found these types of roadcuts to be fascinating, and I consider them to be better (more scenic? an attempt at a "natural" look?) than some types of wholesale roadcut destruction.
An original part of the roadcut can be seen in the gully ahead, although I imagine it might be hard to examine.
Moving along past Deer Creek Reservoir, we finally came into a downpour. Visibility was worse than shown in this photo, for several miles. We were entering the part of the west that was having an abnormally wet monsoon, although we didn't realize how wet it would really be until later.
With it still raining, we finally hooked up with U.S. 40, which we had lost in Salt Lake City before we started our unplanned side trip through the Wasatch via American Fork Canyon and Utah S.R. 92.
When I first started this series last summer or fall, I was really planning on doing more with it than I seem to have time for now, and I was planning on making notes about the geology on the road trip and the formations being seen in these photos. I also have been keeping the locations of photos up to date on the map seen in the last post (link here, not updated at the moment). I'm finding this level of detail to be just too much at this point, so am going ahead with things the way they are right now.

What I noticed when looking up info about the rock formations on this part of the trip and in the last post, was that it's possible that the Bear Canyon member of the Oquirrh Formation and Ely Limestone may be at least in part correlative (also mentioned here). It's a similar age (or the same?), reportedly has abundant nodules of black chert (Geolex), and some fossils in certain parts of the Oquirrh have been tentatively identified in rocks possibly correlative with the Ely (1998 paper here).

Selected References:
Baker, A.A., and Crittenden, M.D., Jr., 1961, Geology of the
Timpanogos Cave quadrangle, Utah: U.S. Geological Survey
Geologic Quadrangle Map, GQ-132, 2 sheets, scale 1:24,000.

Interactive geologic map of Utah (UGS)

My initial notes: Bridal Veil overlies Manning Cnyn Shale, but although the next formation we see looks like it could be a shale, it's more of the Bear Canyon Member of the Oquirrh. This was named as the basal member of the Oquirrh Fm in an area where the Bridal Veil Limestone does not occur or doesn't otcp.

Geloex (Bear Canyon): says "gray to tan and reddish-brown, limy to quartzitic sandstone with thin to thick beds of gray to black limestone, in part sandy, and in part with abundant nodules and stringers of black chert" -- both of these units, their age and description (and not so much what I've seen of their otcp or exposure) remind me of the Ely Limestone, which we saw here and here (search blog="oquirrh" for one, including "ely") (blah blah). And indeed, the fossils within certain parts of the Oquirrh have been tentatively identified in rocks possibly considered part of the Ely (1998 paper here)

Going back to Roberts Horn (last post) and here - it might even look like the Ely!

Related Posts:
Across the West and Back Day 2: Over the Wasatch Range
Across the West and Back Day 2: Are We Lost Yet?
Across the West and Back Day 2: A Hike along a Limestone Ridge
Across the West and Back Day 2: Across the Salt Lake Desert
Across the West and Back Day 2: A Side Trip in West Wendover
Across the West and Back Day 2: Pequop Summit to West Wendover
Across the West and Back Day 2: Looking for an Old Roadcut
Across the West and Back: The First Day
Intro to Recent Western Loop Trip

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