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Ordovician rocks in Illinois are divided into three series, each separated by an unconformity; from oldest to youngest, these are the Canadian, Champlainian, and Cincinnatian series. Ordovician features in Illinois include the now-buried Glasford Structure in Peoria County , a crater caused by a meteorite impact roughly 455 million years ago.
A gap in the local rock record spans the entire Permian period, so there are no rocks of this age in Illinois in which fossils could have been preserved. [2] However, one notable local event following the Pennsylvanian was the meteor impact that occurred near modern Des Plaines. [13]
The type locality is the Mazon River (or Mazon Creek), a tributary of the Illinois River near Morris, Grundy County, Illinois. The 25 to 30 meters of shale were formed approximately , during the Pennsylvanian period. The fossiliferous concretions are usually found within the thickest deposits of the Francis Creek Shale.
The oldest fluvial sediments, which overlay bedrock in the deepest part of the valley, were dated by OSL dating to around 190,000 BP. [ 8 ] [ 9 ] These OSL dates demonstrate that the Illinoian Stage is temporarily equivalent only to Marine Isotope Stage 6, which ended at 130,000 BP and started at 191,000 BP. [ 6 ]
The Illinois Basin is a Paleozoic depositional and structural basin in the United States, centered in and underlying most of the state of Illinois, and extending into southwestern Indiana and western Kentucky. The basin is elongate, extending approximately 400 miles (640 km) northwest-southeast, and 200 miles (320 km) southwest-northeast.
In Illinois, Castle Rock is a large bluff of St. Peter Sandstone, and Starved Rock State Park and Matthiessen State Park feature numerous outcroppings and canyons. Commercial use [ edit ]
[2] [3] [10] [11] More recent geologic mapping, coring, and optically stimulated luminescence (OSL) dating of Illinoian glacial tills (Glasford Formation) and outwash (Pearl Formation) of the Illinoian Glacial Lobe in North-central Illinois demonstrates that the start of the Illinoian stage and end of the Pre-Illinoian stage correlates with the ...
It exists in Missouri, Wisconsin, Iowa, Illinois, and Indiana. It is equivalent to the all but the basal formations of the Cincinnati Group in Ohio. Illinois and Indiana are the only states where the Maquoketa is considered a group. In other states it is a formation. The Maquoketa was deposited in a shallow intercontinental sea.