Tuesday, March 14, 2017

The Roan Cliffs Again, This Time with Some Contacts

After seeing Ron Schott's awesome and enlightening GigaPan of the Roan Cliffs, I decided I had to mark some contacts on the photos from my last post (and partly because what I said or implied about the formations were a little off). To deduce the location of these contacts, I extrapolated from this USGS preliminary geologic map, using the USGS TNM 2.0 Viewer and Google Earth.
In the first photo, it's still a toss-up, imo, as to whether the Tertiary Uinta Formation (Tu) can be seen—but if so, it's way up at the top of the cliff. Most or all of the cliff and most of the slope is underlain by the Tertiary Green River Formation (Tg). Aaaaand maybe there's a bit of the Tertiary Wasatch Formation (Tw) at the bottom of the photo.
In the second photo, there is (probably) just a tiny bit of the lower part of the Uinta Formation (Tu) above the cliffy area, and the reddish-brown foreground slopes are underlain by the Wasatch Formation (Tw). The rest, cliff and slope, consists of Green River Formation (Tg).

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