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Pennsylvanian and Permian nearshore facies on the eastern shelf of north-central Texas contain channel-fill sandstone bodies, which have been mapped from the outcrop westward down the paleoslope for 50 miles. These elongate sandstone bodies range in width from several yards to 3-4 miles and in a few places are more than 100 feet thick. Where the thickness values of the subsurface dendritic (distributary) sandstone bodies are unusually great, sandstone from subjacent bar-finger deposits probably has been included.

Within shallow, poorly developed synclines, which apparently provided primary paleotopographic control of channels, superposed channel systems commonly are offset laterally as a result of (1) interchannel subsidence by differential sandstone (channel)-shale (interchannel) compaction and (2) channel subsidence by compaction of sediments beneath massive channel-fill sandstones. The common offset patterns of superposed channel pairs is mainly a result of dominant interchannel compaction. Stacked or cross-over relations of channel pairs are less common and occur where the lower member is unusually thick. Channel-pair intersect maps illustrate the persistent geographic position of stacking and cross-overs, which may reflect tectonic control of channel location.

Because of differential sandstone-shale compaction, axes of sandstone bodies commonly coincide with maximum thicknesses of thin, conformity-bounded sequences which enclose the elongate sandstone body. Axes representing maximum thickness of these enveloping strata, supplemented by high sandstone percentage trends, and synclinal axes, are useful in outlining the general position of channel-fill sandstone systems, but sandstone isopachous maps, paleotopographic maps, and cross sections (necessitating denser well control) are more definitive.

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