Genetic Types of Some Sandstones in the Allegheny Formation of Ohio: ABSTRACT

Abstract

Sandstones between the Middle Kittanning and Lower Freeport coal beds in the Allegheny Formation of southeastern Ohio are divisible into three genetic categories based on gross external morphology of the sand body, proportion of major mineral components, grain size, and homogeneity of cross-bed orientation. The following types are continuously arrayed in eastwest trending bands along a northeast-southwest outcrop: 1) Thin, lenticular, discontinuous sand bodies with quartz content about 58 per cent. Among all other constituents, feldspar averages 15 per cent, muscovite 25 per cent, chlorite-biotite 60 per cent. Sands are predominantly fine to medium grained and cross-bedding is randomly oriented. 2) Thick, less widespread, partly continuous, elongate sand bodies in which quartz averages 54 per cent. Among all other constituents, feldspar, averages 25 per cent, muscovite 30 per cent, chlorite-biotite 45 per cent. Sand is medium grained and cross-bedding is weakly oriented. 3) Thick, widespread apron or sheet sands in which quartz averages 62 per cent. Among all other constituents, feldspar averages 35 per cent, muscovite 30 per cent, chlorite-biotite 35 per cent. Sands are predominantly medium to coarse grained and cross-bedding is oriented in a northwest-southeast direction. Type 1, found in the southern part of the area, is believed to represent a meandering, relatively nearshore portion of a fluvial system. In contrast, Type 3, found in the northern part of the area, probably represents sand distribution beyond the area of well-developed channels, perhaps near distributary mouths. Type 2, found between areas of Types 1 and 3, presumably reflects an intermediate situation. End_of_Article - Last_Page 340------------