Geological and Dispositional History of the Starved Rocks, Illinois

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Geological and Dispositional History of the Starved Rocks, Illinois

Describe the clastic and carbonate facies you have discovered.
Starved Rock State covers about 200 miles and some 470 million years, from Ordovician sandstones to Pleistocene glacial till. The Ordovician St. Peter Formation sandstone was deposited across the midcontinent during the second major marine transgression of the Paleozoic Era. The first transgression deposited Upper Cambrian to Lower Ordovician clastics and carbonates. The clastic to carbonate rock transition is consistent with gradual sea level rise over the North American craton. Sea level dropped late in the early Ordovician, exposing the carbonate strata to processes of cave development.
The St. Peter sandstone lies in an unconformity. It is 250 feet thick, it can be up to 500 feet thick and it fills erosional channels in the underlying strata. Buffalo Rock is an erosional remnant of Ordovician St. Peter Sandstone and overlying Pennsylvanian clastics. Sign for swift, turbulent, and deep water includes gravel bars and erosional features that are 180 feet above the current level of the river and massive cross bedded sand and gravel deposits along the river course.
The shelf-edge includes carbonate-to-clastic facies transition and tectonic uplift and erosion of the carbonates followed by deposition of the clastics. The Saint Peter Sandstone is a well-sorted, almost pure quartz arenite deposited during a major mid-Ordovician low stand. Clastics spread across an exposed carbonate platform by transportation. This is shown by the well-rounded, frosted texture of the quartz grains.
The Starved Rock Member of the Saint Peter Sandstone is preserved as a northeast-southwest trending belt of strata that is ...

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...i.htm http://www.clays.org/annual%20meeting/50th_annual_meeting_website/docs/CMS13-Fieldtrip-Guide-StarvedRock.pdf http://www2.wheaton.edu/ACG/ASA%20Geology%20Field%20Trip.pdf http://books.google.com/books?id=m35IAgAAQBAJ&pg=PA221&lpg=PA221&dq=facies+at+starved+rock&source=bl&ots=CrHoOg8IHt&sig=9INjch71XPZltMLYoESWy-04lpY&hl=en&sa=X&ei=nk9kU6_DONOQyATNvYCoCw&ved=0CF0Q6AEwBzgU#v=onepage&q=facies%20at%20starved%20rock&f=false http://www2.wheaton.edu/ACG/ASA%20Geology%20Field%20Trip.pdf http://archive.org/stream/starvedrockstate00saue/starvedrockstate00saue_djvu.txt Illinois State Geological Survey, 2005, Time Talks – The Geology of Starved Rock and Matthiessen State Parks
Mikculic, D. G., Sargent, M. L., Norby, R. D., and Kolata, D. R., 1985, Silurian Geology of the Des Plaines River Valley, Northeastern Illinois, Illinois State Geological Survey Guidebook 17, 56p.

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