The first day in the field we visited the "Great Unconfomity" at Frenchman Mountain, just east of Las Vegas. At this location, Paleozoic strata overlie PreCambrian schist and granite in a special kind of unconformity know as a nonconformity. This unconformity is called "Great" because it represents approximately 1.2 billion years (or about 25% of the Earth's age). These strata are equivalent to those found in the bottom of the Grand Canyon.
In the image above, students investigate the Great Unconformity (along a diagonal plane running from the feet of the student on the left to just behind the one on the upper right). The layered rocks above this boundary are those of the Cambrian Tapeats Sandstone. From left to right: Ashley Gentry, Garrett Adams, Dr. Lee Phillips, and Bryan Chavis.
In this image, field trippers walk across the valley occupied by the Bright Angel Shale (overlying the Tapeats Sandstone) toward the next ridge of Muav Limestone.
The above image is a view of Las Vegas from the Muav Limestone ridge.
Updated: Wednesday, January 12, 2011
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