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The Devonian Mahantango Formation is a mapped bedrock unit in Pennsylvania, New Jersey, New York and Maryland. It is named for the North branch of the Mahantango Creek in Perry and Juniata counties in Pennsylvania. It is a member of the Hamilton Group, along with the underlying the Marcellus Formation Shale.〔 South of Tuscarora Mountain in south central Pennsylvania, the lower members of this unit were also mapped as the Montebello Formation. ==Description== The Mahantango is defined as a gray, brown, and olive siltstone and shale,〔Berg, T.M., Edmunds, W.E., Geyer, A.R. and others, compilers, (1980). Geologic Map of Pennsylvania: Pennsylvania Geologic Survey, Map 1, scale 1:250,000.〕 characterized by coarsening-upward cycles. It is typically found conformally overlying the Marcellus Formation, and underlying the Tully Limestone (where present).〔 The Mahantango has been divided into four members:〔MacLachlan, D.B., Hoskins, D.M., Payne, D.F., (1995). Bedrock Geology of the Freeburg 7.5 minuet Quadrangle, Snyder County, Pennsylvania. ORF 95-04, The Pennsylvania Geologic Survey, Harrisburg, PA.〕 *Tully Limestone: a fossiliferous calcaerous shale. The Tully is a conspicuous formation, which separates the Mahantango from the Hamilton Group. *Sherman Ridge: Olive gray, fossiliferous, claystone and siltstone with interbedded fine sandstone coarsening upward. *Montebello Sandstone: Olive gray, fossiliferous, coarse to fine-grained sandstone, interbedded with siltstone and claystone, in coarsening upward cycles. *Fisher Ridge (also described as the Dalmatia and Turkey Ridge): silty claystone, siltstone, and very fine-grained sandstone. The Sherman Ridge and Fisher Ridge are ridge-formers. In south-central Pennsylvania, the Mahantango includes the Clearville, Frame, Chaneysville, and Gander Run Members. 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「Mahantango Formation」の詳細全文を読む スポンサード リンク
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