Wednesday, September 11, 2013

Across the West and Back Day 2: Looking for an Old Roadcut

We left Elko early on the second day and stopped at a little cafế in Wells for breakfast.
I couldn't help but take a couple photos of the interior (!).

A Relevant Aside: Because this part of the trip was across the route of Historic U.S. 40 (now mostly defunct and nowhere signed in Nevada), the drive took me back in time to a cross-country family trip made on U.S. 40 from the west to east coast in 1957, then back east to west about a year later. I was quite young at the time, so have only a few vignettes from the trip stored in my memory. One is of a roadcut somewhere in the west, where we stopped, and I collected my first specimen of slate.

Much later, on a field trip the first year I came to Nevada for grad school — or on a trip to the GSA meeting in SLC that same fall, I saw the roadcut, and it was like dếjấ vu all over again — except this time I *had* been there, about two decades prior. The roadcut, therefore, was either on a section of I-80 between Battle Mountain and Elko (there are very few roadcuts west of Battle Mountain), or on a then still extant section of U.S. 40 between Carlin and the Utah border where I-80 was incomplete. I saw the roadcut then; maybe I saw it again on a 1982 trip to SLC for the GSA Cordilleran section meeting. Have I seen it since? Not sure.

I-80 through over Pequop Summit was still shown as not being completed on the 1987-1988 state highway map, and it was only shown as complete upon the issuance of the 1989-1990 map (I find it hard to believe that the interstate was only completed sometime between 1987 and 1989 or so, but there it is). Also see the 1975 map for the then current state of affairs during my first couple trips across the state that fall.

Back to the trip: At about 8:20, we started up the west side of the Pequop Mountains and began seeing our favorite limestone: the Ely Limestone (or maybe it's called something else in northeastern Nevada, like Etchart?). This section of road probably closely follows the original route of U.S. 40 through the mountains, and it goes through exposures of bedded to flaggy-looking Ely Limestone and shaly Chainman Shale below that.
Ely Limestone.
In the Pequops, I thought I saw a couple roadcuts that looked like the one I remember from long ago, but the ones that really struck me are probably in Ely Limestone.

Looking carefully at the satellite view of the area on Google Maps, I can deduce that the [articular roadcut shown below might be (partly) in Chainman Shale, although really, most of the exposure looks like limestone.
Ely Limestone on the right, a fault in shadow in the upper left; possible Chainman Shale left of the fault (barely in the photo).
By the time we were approaching the Pequop exit on the east side of the summit, I had seen several possibilities for the original roadcut, but I'm not sure that any of them fit the bill. Perhaps it was in the westbound lane on a section where the lanes diverge. Perhaps the roadcut has been modified beyond recognition since I last saw it. Perhaps it was really on some other leg of U.S. 40 in Nevada or Utah. In any case, I enjoyed seeing the Ely Limestone through this part of the trip and recognizing the Chainman Shale in exposures below it (mostly in the surrounding hills and not in the roadcuts) .
We approach the Pequop exit and can see part of the Toano Range across Goshute Valley.
I'm going to stop here for now, otherwise this will never get posted! I've got the Day 2 trip route in Google Maps below, with locations of photos taken during the day — I'll add to this as I post more photos. I've also shown several roadcuts of of interest where I took photos, roadcuts I later decided were most likely in Ely Limestone. Note the conspicuous divergence of the eastbound lane from the westbound lane in the middle of the Pequops. This divergence leaves a roadcut possibility to check out on some other trip.

View Day 2: Elko, NV to Vernal, UT in a larger map

Related Posts:
Across the West and Back: The First Day
Intro to Recent Western Loop Trip

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