- Madison Limestone
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Age and nomenclature
The Madison is formally known as the Madison Group. In Montana, where its thickness reaches convert|1700|ft|m|-1, the group is subdivided into the Mission Canyon Formation and Lodgepole Formation. Equivalents of the Madison are named the Pahasapa Limestone in the Black Hills, Leadville Limestone (Colorado), Guernsey Limestone (Wyoming), and
Redwall Limestone in the Grand Canyon. The upper part of the Madison Group, the Charles Formation in the subsurface of North Dakota and northern Montana, is not strictly an equivalent of the Madison Limestone as usually defined. [Mississippian System, by Lawrence C. Craig, in "Geologic Atlas of the Rocky Mountain Region", Rocky Mountain Association of Geologists, Denver, CO, 1972: p. 100-110]Most of the Madison Limestones were deposited during Early to Middle Mississippian time (
Tournaisian toVisean stages), about 359 to 326 million years ago. Older North American usage lists the Madison as being laid down during the Kinderhookian, Osagian, and Meramecian stages.Neither a type locality nor derivation of the name was designated when the term "Madison Limestone" was first used by Peale (1893), [ [http://3dparks.wr.usgs.gov/coloradoplateau/lexicon/madison.htm Peale, A.C., 1893, "The Paleozoic section in the vicinity of Three Forks, Montana, with petrographic notes by G.P. Merrill": U.S. Geological Survey Bulletin, 110, 56 p.] ] but since the original work focused on the area of
Three Forks, Montana , it is likely that the name relates to outcrops along theMadison River , Montana. A reference section has been designated on the north side of Gibson Reservoir in SE/4 sec. 36, T. 22 N., R. 10 W., Patricks Basin quad, Teton Co., Montana. [Mudge, M.R., Sando, W.J. and Dutro, J.T., Jr., 1962, "Mississippian rocks of the Sun River Canyon area, Sawtooth Range, Montana": American Association of Petroleum Geologists Bulletin, v. 46, no. 11, p. 2003-2018]Lithologies
Limestone s anddolomite s dominate the Madison. Because the rock is highly soluble, it often develops caves andkarst topography.Lewis and Clark Caverns , Montana, is an example of a cave developed in the Madison. The rocks were deposited in a generally shallow marine setting, indicated by the richly fossiliferous rocks of the Madison. In theWilliston Basin , water was shallow enough foroolite shoals to develop; they later became reservoirs for oil. [ [http://aapgbull.geoscienceworld.org/cgi/content/abstract/39/11/2170 "Mississippian Madison group stratigraphy and sedimentation in Wyoming and southern Montana", by John Michael Andrichuk, AAPG Bulletin; November 1955; v. 39; no. 11; p. 2170-2210] ] The gray cliffs along theMissouri River in the Gates of the Mountains, Montana are formed by Madison Limestone. ["River Log and Road Log: Thrust Faulting near Gates of the Mountains, Lombard, Lewis & Clark Canyon", Montana Geological Society 1994 Guidebook, James L. Cannon, Gary G. Thompson, and John R. Warne, editors]References
ee also
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List of types of limestone
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