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Geologic History of the Illinois Valley

Geologic History of the Illinois Valley. Mike Phillips Geology Professor Illinois Valley Community College. Illinois Rocks. Igneous & Metamorphic: in the “Basement” Sedimentary: bedrock Unconsolidated material: on the surface. Rocks of north-central Illinois.

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Geologic History of the Illinois Valley

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  1. Geologic History of the Illinois Valley Mike Phillips Geology Professor Illinois Valley Community College

  2. Illinois Rocks • Igneous & Metamorphic: in the “Basement” • Sedimentary: bedrock • Unconsolidated material: on the surface

  3. Rocks of north-central Illinois Exposures in the upper Illinois Valley: • Ordovician • Ottawa & Starved Rock • Silurian • Des Plaines R. • Pennsylvanian • remainder

  4. Rocks of the central Illinois Valley • Ordovician (505 to 438 MYA) • Shakopee Dolostone: shallow marine • St. Peter Sandstone: beach • Galena-Platteville Dolostone: shallow marine • Silurian (438 to 417 MYA) • dolostone: shallow marine • Silurian-Mississippian (417 to 320 MYA) • No rocks exposed: eroded or not deposited • LaSalle Anticline: fold

  5. Rocks of the central Illinois Valley • Pennsylvanian (320 to 286 MYA) • Carbondale • Bond • Modesto

  6. Rocks of the central Illinois Valley • Pennsylvanian cyclothems • thin layers of varying type in repeated sequences • coal • sandstone • limestone • shale • clay • varying coastal env. • fluctuating sea level

  7. Permian to Quaternary (286 to 1.8 MYA) • erosion

  8. Pleistocene(1.8 MYA to10,000 YA) • Unconsolidated deposits • diamicton • sand and gravel • sand dunes (near the river) • loess • laminated clay

  9. TheICEAGE

  10. 10,000 YA to present

  11. Thank You Mike Phillips Illinois Valley Community College www.ivcc.edu/phillips mike_phillips@ivcc.edu (815)224-0394 “The Geologic History of The Illinois Valley” June 2006

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