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  • The Warsaw Shale is named for Warsaw, Hancock County, and the exposure in Geode Glen at Warsaw has become the type section. The Warsaw is widely present in the bluffs of the Mississippi and Illinois Valleys in western and southwestern Illinois. It consists of as much as 300 feet of siltstone in west-central Illinois, but it thins to less than 100 feet in the outcrop area, where it consists of gray shale containing beds of argillaceous limestone. Quartz geodes are common and locally abundant; some are replacements of fossils. Some contain petroleum. The Warsaw is fossiliferous, with brachiopods, bryozoans, and crinoids especially common.
  • The point in a well or opening in the Earth where groundwater begins. It generally marks the top of the zone where the pores in the surrounding rocks are fully saturated with water.
  • The group of processes, chemical and physical, whereby rocks on exposure to the weather, change in character, decay, and finally crumble into soil.
  • Pertaining to the classical fourth glacial stage (and the last definitely ascertained, although there appear to be others) of the Pleistocene Epoch in North America, following the Sangamonian interglacial stage and preceding the Holocene.
  • Layer of sediment named for the village of Wedron and the Wedron Quarry, where strata of Quaternary sediments (tills and proglacial river and lake sediments) are well exposed above bedrock in pits in which silica sand is being mined.