Title: Aspects of Early Allegheny Depositional Environments in Eastern Ohio.
Abstract: Lower Allegheny rocks o f Middle Pennsylvanian age in eastern Ohio comprise a variety of chemical and detrital rock types each presumably reflecting a particular environ ment of deposition.Temporally and spatially these environments had a complex albeit systematic chronological arrangement, the reconstruction of which was achieved b y collecting, analyzing, and integrating the data from both field study of the spatial relationships of rock types and detailed study of some of the chemical components (iron stones and limestones).Results from these lines of evi dence were interpreted in light of information from similar studies in southern Ohio and western Pennyslvania.D e p o sition of the lower Allegheny rocks was apparently in and around a complex set of prograding deltaic wedges.The direction of progradation was generally northward against a relatively static shoreline.Loci of deposition shifted constantly in a seaward direction with each wedge of detrital sediments passing through a cycle of subsidence, stagnation, and transgression during which chemical deposition dominated.Each "dying" phase was followed by a new episode of active sedimentation. 2 General Geology Lower Allegheny strata in eastern Ohio crop out along the west flank of the Allegheny Synclinorium (figure 1).Allegheny rocks in the southern part of the area dip about 1 0 0 feet per mile to the east and in the northern part about 50 feet per mile to the south.Lower Allegheny beds vary in thickness from 50 to 125 feet and consist of a great variety of thin, often discontinuous sandstones, siltstones, shales, coals, "underclays," and limestones which are not grossly dissimilar to those of the underlying Pottsville and overlying Allegheny strata.Among detrital rocks, sandstones are more abundant in the south whereas shales and siltstones are more abundant in the northern part of the area.Marine limestones and other zones bearing marine fossils are more prevalent in the north than in the south and coal beds seem to be about equally distributed throughout the area.