More on the MYRES field trip, this time from the western
side of the San Rafael Swell! After admiring the amazing geomorphological
expression of the San Rafael Swell (see blog entry from 09/07/2012) we drove
west through Spotted Wolf Canyon. This is the description that we had on our
Field Trip guide (prepared by MYRES organizers):
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| From http://americanindian.net/utah2006l.html |
“This section of the highway was the first road to breach
the steep eastern side of the Swell and was not completed until 1970. This rest
area provides an overlook of Black Dragon Canyon, with views of the bright red
cliff-forming sandstones in the Triassic units in the eastern part of the
Swell. As you look into Black Dragon Canyon you are stratigraphically at or
very near the Permian-Triassic boundary (~248 Ma), marked by what is believed
to have been the most extensive mass-extinction event in the geologic record.
The rest area itself is located on the uppermost part of the Kaibab Formation
(Permian); this is the same limestone unit that forms the rim of the Grand
Canyon, several hundred miles south in Arizona (here the Kaibab Formation is
near its northernmost and easternmost extent before pinching out). Below the
Kaibab Formation, exposed in the walls of Black Dragon Canyon, is a Permian
sandstone known as the White Rim Sandstone. This white to yellow-white
cross-bedded eolian sandstone is a terrestrial equivalent of the marine
Toroweap Formation in Grand in Grand Canyon, Arizona”
