OMAHA! If I timed this right, this post will go up while a guy in an orange sporting jersey is, for

OMAHA! If I timed this right, this post will go up while a guy in an orange sporting jersey is, for some reason I don’t really get, yelling out the word “Omaha!” several dozen times. This photo shows some outcrops of the Dakota formation…which happens to underlie the area around Omaha, Nebraska. The Dakota formation is a sandstone. It is cretaceous in age, formed when sea levels were much higher and a shallow ocean covered much of the interior of the North American continent. The sandstones were deposited in environments near the shoreline of this seaway as the water levels rose and fell. The sand grains were delivered from rivers that were eroding both the Rocky Mountains in the west and higher ground in the east. Those rivers carried sand and mud to the continent’s interior, where it was deposited, buried, and gradually cemented into sandstones. Today this formation underlies much of the Great Plains. It runs from Nebraska in the south to Minnesota in the north, with a thickness of about 100 meters. In Nebraska, there are a variety of sediments on top of it, including the thick Pierre clay, deposited when the Cretaceous seaway became deeper, and the younger sediments deposited during the recent glacial periods. Sandstones have quite a bit of pore space; open gaps between the sediment grains which can fill with water. The Dakota Sandstone, although deeply buried in places, hosts a variety of aquifers that have been tapped for irrigation in places. The waters are supplied in the areas near Omaha and near the Rocky Mountain front, where the unit outcrops at the surface. -JBB Image credit: Kansas Geological Surveyhttp://www.kgs.ku.edu/Publications/Bulletins/ED10/04_occur.html Read more:http://www.nps.gov/history/history/online_books/geology/publications/pp/17/images/plate10.pdfhttp://www.nps.gov/history/history/online_books/geology/publications/pp/17/sec2.htm -- source link

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