Midcontinent Rift System
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The Midcontinent Rift System (MRS) or Keweenawan Rift is a 2000 km. long geological rift in the center of the North American continent and south-central part of the North American plate. It trends north from central lower Michigan, turns west through Lake Superior with its outer arc following the line of the north shore of that lake in Minnesota and Ontario, then turns southwest through portions of Wisconsin, Minnesota, Iowa, Nebraska and Kansas.[1] It is approximately 1,100 million years old, from the Precambrian Mesoproterozoic era.
Near Lake Superior, rocks produced by this rift can be found on the surface along the shores of the Keweenaw Peninsula of Upper Michigan,[2] and on the North Shore of the lake in Minnesota.[3] The lake itself lies in the rift valley formed by the rifting. Further south, the rift is buried thousands of feet below the surface. Where buried, it has been mapped by gravity anomalies (its dense basaltic rock increases gravity locally),[4] aeromagnetic surveys,[5] and seismic data.[6] Deep drilling for commercial oil and gas exploration has penetrated the rift and made rock samples available.
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[edit] References
[edit] Notes
- ^ Iowa Geological Survey. Location of the Midcontinent Rift System (map). Iowa DNR. Retrieved on 2007-03-22.
- ^ Raymond R. Anderson, The Midcontinent Rift System in Iowa, Iowa DNR - Geological Survey Retrieved 2007-01-07
- ^ Ojakangas, Richard W.; Charles L. Matsch (1982). Minnesota's Geology, Illus. Dan Breedy, Minneapolis, Minnesota: University of Minnesota Press. ISBN 0-8166-0953-5.
- ^ Gravity anomaly map of north-central United States, data compiled by D. Daniels and S. Snyder, U.S. Geological Survey Retrieved 2007-01-14
- ^ Magnetic intensity anomoly map for north-central United States, data compiled by D. Daniels and S. Snyder, U.S. Geological Survey Retrieved 2007-01-14
- ^ W. Hinze, D. Kellog, and D. Merritt, Gravity and Aeromagnetic Anomaly Maps of the Southern Penninsula of Michigan, Mich. State Geological Survey Retrieved 2007-01-07
[edit] Maps
- T. Bornhorst (Michigan Tech), L. Woodruff (USGS), and S. Nicholson (USGS), Stratigraphy, Structure, and Ore Deposits of the Southern Limb of the Midcontinent Rift System, Minnesota Geological Circular XXX (western Lake Superior)
