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File:Geology of the Richmond Basin 1899 Plate XXX.jpg

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Summary

Description
English: Plate XXX from The Geology of the Richmond Basin published by USGS, which has the following caption:
Grit lenses and bleached joints in basal Newark shales, western border (of the Richmond Basin), south of Mosley Junction. Looking south.
The text of the report refers to the figure as follows:
That the strata of the basin vary in thickness from point to point along the strike is indicated by the thinning of the coal beds and by their occasional confluence in this direction. The beds of sandstone and shales outside of the coal-bearing zone have not been, and can not be, traced with that accuracy which would permit a definite statement as to their uniformity and extent. The local unconformities which have been observed in the upper parts of the section (see p. 440), notably in the central part of the basin, show that the shales have been partly denuded before the deposition of the overlying sands and grits. Where this process of local erosion has occurred in this basin, the bedding is discontinuous and lenticular, as we might expect. The small lenses of grit in the shales and sands of the western margin point to the same conclusion (see Pl. XXX). In fact, a comparison of the Turkey Branch section, giving a nearly complete exhibit of the strata near the base on the western margin, with the familiar strata of the same place in the section on the eastern margin, shows that there is a marked change in the lithologic and structural characters between the two points. Similar evidence is derived from the distribution of the coal beds. While their failure to appear at certain points on the upturned margin may be plausibly explained as due to downfaulting of the beds in these places, there are other sections in which their absence is real and is due to a failure to be formed in those places or to their erosion as the prelude to the incursion of coarse sediments. From these considerations we are led to conclude that the strata in the basin are not persistently continuous.
Date
Source Nathaniel Southgate Shaler and Jay Backus Woodworth, 1899. Geology of the Richmond Basin, Virginia. U.S. Government Printing Office. United States Geological Survey.
Author USGS

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Public domain
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Captions

Basal Newark shales

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