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Medicine Rocks State Park
Medicine Rocks State Park is a park owned by the state of Montana in the United States. It is located about west-southwest of Baker, Montana, and north of Ekalaka, Montana. The park is named for the "Medicine Rocks," a series of sandstone pillars similar to hoodoos some high with eerie undulations, holes, and tunnels in them.〔McRae and Jewell, ''Montana,'' 2009, p. 303.〕〔Hawthorn, ''Rocky Mountain States,'' 2001, p. 615.〕 The rocks contain numerous examples of Native American rock art,〔Keyser and Klassen, ''Plains Indian Rock Art,'' 2001, p. 55.〕 and are considered a sacred holy place by Plains Indians.〔Haney, ''Badlands of the High Plains,'' 2001, p. 37.〕 The park is in size and in elevation.〔 It is managed by the Montana Department of Fish, Wildlife and Parks. Theodore Roosevelt said Medicine Rocks was "as fantastically beautiful a place as I have ever seen".〔Quoted in: ''Off the Beaten Path: A Travel Guide to More Than 1,000 Scenic and Interesting Places Still Uncrowded and Inviting,'' 2003, p. 199.〕
==Geology==
Medicine Rocks is part of the Fort Union Formation, a geologic unit containing coal, sandstone, and shale in Montana, Wyoming, and other adjacent states.〔Schalla and Johnson, ''Montana/Alberta Thrust Belt and Adjacent Foreland,'' 2000, p. 104.〕 About 61 million years ago, near the start of the Paleocene Epoch and during the late Zuñi sequence, a freshwater river crossed what is now eastern Montana, flowing southeast into a prehistoric sea whose boundary was near far northwestern South Dakota (possibly the remains of the Western Interior Seaway).〔〔Fletcher, Bradshaw, Axline, and Shope, ''Montana's Historical Highway Markers,'' 2008, p. 195.〕 This river deposited large amounts of very fine-grained sand, which compacted into sandstone.〔〔〔Johnson and Troll, ''Cruisin' the Fossil Freeway: An Epoch Tale of a Scientist and an Artist on the Ultimate 5,000-Mile Paleo Road Trip,'' 2007, p. 81.〕 On top of the freshwater sandstone was sand laid down by a saltwater estuary (indicated by the presence in this greyish layer of sandstone of burrows created by marine worms).〔 Numerous fossils dating back 63.3 million years (to the Torrejonian North American Stage) can be found at the site, which help date the sandstone.〔〔〔 These include several fossil snakes〔Holman, ''Fossil Snakes of North America: Origin, Evolution, Distribution, Paleoecology,'' 2000, p. 94.〕 as well as teeth belonging to ''Plesiadapis anceps'' (an early primate-like mammal).〔Woodburne, ''Late Cretaceous and Cenozoic Mammals of North America: Biostratigraphy and Geochronology,'' 2004, p. 81.〕 The fossil remains of the primitive mammal Baiotomeus were discovered here in 1935.〔Krause, "Baiotomeus, a New Ptilodontid Multituberculate (Mammalia) from the Middle Paleocene of Western North America," ''Journal of Paleontology,'' May 1987.〕
Wind, dirt, sand, and rain carved the sandstone over the millennia, so that now the structures exhibit numerous arches, caves, columns, holes, pillars, and flat-topped towers.〔''Off the Beaten Path: A Travel Guide to More Than 1,000 Scenic and Interesting Places Still Uncrowded and Inviting,'' 2003, p. 199.〕 Some of the sandstone structures are in height,〔〔 and can be across.〔 There are more than 100 of the rocks and spires in the state park today.〔 Some of them are clustered together as if part of a chain or train, while others jut up from the prairie in isolation.〔
According to Ed Belt, retired professor of geology at Amherst College, the Medicine Rocks sandstone is almost unique. "You have to go a long way to find a sand deposit of a similar age. And even then, you won't find thick sand and such a large concentration like you have at Medicine Rocks."〔 It is also possible that the state park lies atop an unexposed fault.〔
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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