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The Pittsburgh Coal Seam is the thickest and most extensive coal bed in the Appalachian Basin;〔Susan J. Tewalt, Leslie F. Ruppert, Linda J. Bragg, Richard W. Carlton, David K. Brezinski, Rachel N. Wallack, and David T. Butler, 2000. Chapter C - A Digital Resource Model of the Upper Pennsylvanian Pittsburgh Coal Bed, Monongahela Group, Northern Appalachian Basin Coal Region. U.S. Geological Survey Professional Paper 1625–C, 106 p. http://pubs.usgs.gov/pp/p1625c/CHAPTER_C/CHAPTER_C.pdf〕 hence, it is the most economically important coal beds in the eastern United States. The Upper Pennsylvanian Pittsburgh coal bed of the Monongahela Group is extensive and continuous, extending over 11,000 mi2 through 53 counties. It extends from Allegany County, Maryland to Belmont County, Ohio and from Allegheny County, Pennsylvania southwest to Putnam County, West Virginia.〔L. Ruppert, S. Tewalt, L. Bragg, (Map Showing Areal Extent of the Pittsburgh Coal Bed and Horizon and Mines Areas of the Pittsburgh Coal Bed ), U. S. Geological Survey Open file Report 96-280, 1997〕〔(Selected Geologic Factors Affecting Mining of the Pittsburgh Coalbed ), United States Bureau of Mines, RI 8093, 1975〕 This coal seam is named for its outcrop high on the sheer north face of Mount Washington in Pittsburgh, Pennsylvania,〔(Geology of Point State Park ), Pittsburgh Geological Society, no date.〕 and it is considered to form the base of the upper coal measures of the Allegheny Plateau,〔Strategraphy of the Bituminous Coal Field in Pennsylvania, Ohio and West Virginia, (Bulletin of the United States Geological Survey No. 65 ), Washington, Government Printing Office, 1891. See Chapter III.〕 now known as the Monongahela Group.〔Raymond C. Moore and M. L. Thompson, (Main Divisions of the Pennsylvanian Period and System ), Bulletin of the American Association of Petroleum Geologists, 33, 3 (March 1949) pages 279–280〕 The first reference to the Pittsburgh coal bed, named by H.D. Rodgers of the First Geological Survey of Pennsylvania,〔White, I.C., 1898, The Pittsburgh coal bed: American Geologist, v. 21, p. 49–60〕 was on a 1751 map.〔Eavenson, H.N., 1938, The Pittsburgh coal bed; its early history and development: American Institute of Mining and Metallurgical Engineers Transactions, v. 130, p. 1–55〕 The section of the Pittsburgh seam under the Georges Creek Valley of Western Maryland is known as The Big Vein 〔C. M. Young, Percentage of Extraction on of Bituminous Coal with Special Reference to Illinois Conditions, (Engineering Experiment Station Bulletin No. 100 ), University of Illinois, June 1917, page 90.〕 This is isolated from the rest of the Pittsburgh seam by Savage Mountain (part of the Deer Park anticline), the Negro Mountain anticline, the Laurel Hill anticline, and the Chestnut Ridge anticline. Between these anticlines, the strata containing the Pittsburgh coal have been almost obliterated by erosion. The exception is a small remnant in Somerset County, Pennsylvania, in the Berlin Syncline between Negro Mountain and Savage Mountain.〔(Geology and Mining Activities ), Mine Drainage Pollution Abatement Project, Commonwealth of Pennsylvania Department of Environmental Resources, no date, see Figs 1 and 8.〕 ==Formation== The Pittsburgh coal is one of many minable coal beds that were deposited across the Pennsylvanian (late Carboniferous) and Permian (330–265mya) eras in a subsiding foreland basin that was filled in with sediments eroded from an ancient landmass located to the east.〔Hatcher, R.D., Jr., Thomas, W.A., Geiser, P.A., Snoke, A.W., Mosher, S., and Wiltschko, D.V., 1989, Alleghanian orogen, in Hatcher, R.D., Jr., Thomas, W.A., and Viele, G.W., eds., The Appalachian-Ouachita orogen in the United States: Boulder, Colo., Geological Society of America, The Geology of North America, v. F–2, p. 223–231〕 The Monongahela Group and other northern and central Appalachian Basin (fig. 1) Pennsylvanian sediments were deposited on an aggrading and prograding coastal plain within a foreland basin adjacent to the Alleghanian fold and thrust belt.〔Dominic, D.F., 1991. Controls on alluvial stratigraphy in the Upper Pennsylvanian-Lower Permian Dunkard basin (): American Association of Petroleum Geology, v. 75, p. 1182.〕 The Pittsburgh coal bed formed during a hiatus in active clastic deposition that allowed for the development of a huge peat mire. The extensively thick peat deposit was destined to become one of the most valuable energy resources in the world. The distribution of some of the sediments, particularly the channel sands, may have been controlled in part by deep, Early Cambrian basement faults that were reactivated during the Alleghany orogeny (Root and Hoskins, 1977; Root, 1995). Significant parts of the clay layer immediately below the Pittsburgh coal rest on an unconformity, that is, an old eroded surface.〔George W. McNees, Andrew S. McCreath, Richard R. Hice, (Topographic and Geological Survey of Pennsylvania, 1906-1908 ), Harrisburg, 1908, pages 153–154.〕 For this reason, the Pittsburgh seam is taken as the basal member of the Monongahela Group. The underlying erosion surface is considered the top of the Conemaugh Group, formerly known as the Lower barren measures because this formation contains few coal seams. The Monongahela is composed mainly of sandstone, limestone, dolomite, and coal,〔Chapter 5 in "The Effects of Subsidence Resulting from Underground Bituminous Coal Mining on Surface Structures and Features and Water Resources: Second Act 54 Five-Year Report", PADEP, 2005. http://www.dep.state.pa.us/dep/deputate/minres/bmr/act54_2004_report/toc_01_pdf.htm〕 and consists of a series of up to ten cyclothems. During each cyclothem, the land was flooded, allowing the accumulation of marine deposits such as shale, limestone and sandstone. When the sea level fell, coal formed from the remains of swampland. Some of the coal beds in the Monongahela group are erratic, sometimes little more than a black streak in the rock, while others are of commercial importance.〔(Pennsylvanian stratigraphy )〕 The Pittsburgh coal seam is laterally extensive. It commonly occurs in southwestern Pennsylvania in two benches, and the lower bench can be over six feet thick.〔[Roen, J.B., Kent, B.H. and Schweinfurth, S.P., 1968. Geologic map of the Monongahela quadrangle, southwestern Pennsylvania: U.S. Geological Survey, Geologic Quadrangle Map GQ-743. http://ngmdb.usgs.gov/ngm-bin/ILView.pl?sid=2050_1.sid&vtype=b&sfact=1.5〕 The Pittsburgh rider coal bed, which overlies the lower bench, can range from 0 to 3 feet in thickness. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Pittsburgh coal seam」の詳細全文を読む スポンサード リンク
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