Thursday, December 22, 2011

An exhumed paleochannel...

from the Jurassic stands out in relief as a sinuous ridge in these Google Earth images, located about eight miles north of Moab, Utah (that's the intersection of highways 191 and 313 at the top of the first image).  The following image is a view to the southwest (click images to enlarge):
This second image is a view in the opposite direction, toward the northeast.  The dry wash clips the western end of the landform, and coincides with the position of the Moab fault:
The paleochannel is part of the Salt Wash Member of the Morrison Formation, and stands more than five meters above the surrounding shaly strata belonging to the Tidwell Member:
Here's the view from on top, towards the west, where the sinuous geometry is very apparent.  If you look closely, my field vehicle is parked on the Moab fault at the distant end of the landform:
The channel feature is filled with coarse-grained quartz arenite sandstones, with distinct planar-tabular crossbeds that are oriented towards the east, consistent with the basinal dip during the Jurassic:
This bit of field geology was just part of my explorations yesterday of the area around Upper Courthouse Wash west of Arches National Park.  I'll post more later.

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