Wednesday, October 1, 2008

Stratigraphy and Geological History---Pennsylvanian

Before this field trip the first thing we had to learn about so we could understand the rest of the geology was the stratigraphy and geological history of the parks we were going to see. Stratigraphy is a part of geology that studies the layers and layering of sedimentary rocks. For more information on what statigraphy is and how it came about check out Lets talk about the lowest layers seen in these parks. They come from the Pennsylvanian Period which is about 310 million years ago. During this time there was a restricted inland sea. This sea left layers of potash, dolomite, gypsum, salt as it went through different evaporative cycles. The salts form the Paradox Formation (see earlier blog entry about this ) .  These salts easily deform plastically which is responsible for the salt tectonism of this area.  The other formation in this period is the Honaker Trail. This formation has fossiliferous limesone, sandstone, and shale. The Honaker Trail was deposited in a shallow sea and delta.  These two formations make up the Hermosa Group. Wow that was a lot of geology and isn't amazing that we had part of the ocean in Moab, UT.  Crazy what a couple hundred million year difference makes. This is a picture of the Colorado River and it cut down to the Pennsylvanian period rock.

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