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Paleogeographic reconstruction showing the Illinois Basin area during the Middle Devonian period. [9] Almost all Silurian rocks in Illinois are deep-water limestone and dolomite deposits; reef habitats were common, and fossils of reef organisms are locally highly abundant, including corals, brachiopods, crinoids, stromatoporoids, and bryozoans. [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.
Thornton Quarry, just south of Chicago, Illinois. One of the largest aggregate quarries in the world, 1.5 miles (2.4 km) long, 0.5 miles wide, and up to 450 feet deep, site of a Silurian reef. Quarried since 1836. The quarry also acts as an emergency flood control reservoir as part of Chicago Deep Tunnel project.
The Shawnee Hills are often called the "Illinois Ozarks", especially in promotional literature for tourism. But they are technically not a part of The Ozarks , a geologically similar area that for the most part begins just to the west across the Mississippi River floodplain in southeastern Missouri .
The fossiliferous concretions are found in the Mazon River area of Grundy, Will, Kankakee, and Livingston counties. Additional fossils are found in LaSalle County, Illinois; between the Vermilion River and Marseilles, Illinois. The ironstone concretions are recovered from exposures along streams, roadcuts and in active or abandoned coal mine areas.
Illinois' ecology is in a land area of 56,400 square miles (146,000 km 2); the state is 385 miles (620 km) long and 218 miles (351 km) wide and is located between latitude: 36.9540° to 42.4951° N, and longitude: 87.3840° to 91.4244° W, [1] with primarily a humid continental climate.
Watersheds of Illinois is a list of basins or catchment areas into which the State of Illinois can be divided based on the place to which water flows.. At the simplest level, in pre-settlement times, Illinois had two watersheds: the Mississippi River and Lake Michigan, with almost the entire State draining to the Mississippi, except for a small area within a few miles of the Lake.
Granite rock hand-sized sample A granitoid is a broad term referring to a diverse group of coarse-grained igneous rocks that are widely distributed across the globe, covering a significant portion of the Earth's exposed surface and constituting a large part of the continental crust [ 1 ] .