Geology of Kansas

The Geology of Kansas encompasses the geologic history of the US state of Kansas and the present-day rock and soil that is exposed there. Rock that crops out in Kansas was formed during the Phanerozoic eon, which consists of three geologic eras: the Paleozoic, Mesozoic and Cenozoic. Paleozoic rocks at the surface in Kansas are primarily from the Mississippian, Pennsylvanian and Permian periods.

Mushroom Rock, Ellsworth County, Kansas (1916)[1]

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The oldest rocks at the surface in Kansas are Mississippian rocks that consist of limestones, shale, dolomite, chert, sandstones and siltstones. The Mississippian consisted of an environment similar to what we see today. Fast moving streams and rivers cutting into the limestone bedrock and in places creating caverns and sinkholes.[2] Pennsylvanian rocks consist predominantly of alternating marine and non-marine shales and limestones with some sandstone, coal, chert and conglomerate. The Pennsylvanian was a time that the region that is now eastern Kansas stayed nearly at sea level. Between the transgression and regression of the seas, swamps and bogs formed, depositing dead vegetation and later, after burial under younger sediments, this dead vegetation formed into coal.[2] Permian rocks predominantly consist of limestones, shales and evaporites. The Permian in Kansas began as an environment consisting of warm, shallow seas. As the Permian progressed, the climate became very dry and the seas began to subside, creating bodies of water shut off from the open seas, in turn creating areas for the generation of dark shales and evaporite minerals such as halite and gypsum as the waters evaporated.[2] The end of the Permian marks the largest extinction period in Earth’s history; over 90% of all life disappeared.

Mesozoic rocks at the surface in Kansas consist predominantly of rocks from the Cretaceous. A relatively small outcrop of Jurassic sediments are exposed in the southwest corner of the state. Cretaceous age rocks consist of limestone, chalk, shale and sandstone. The Cretaceous in Kansas was an open ocean or sea environment dominated by microscopic marine plants and animals that floated or swam near the surface of this ancient water body.[2] As these microscopic creatures died they sank to the bottom, formed a soft, limy ooze and would preserve any larger creatures that would die and sink into it.

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