Abstract
Exposures of predominantly mid-fan channel deposits from the Tesnus Formation (Upper Mississippian-Lower Pennsylvanian) of West Texas provide an opportunity to examine possible meandering and braided deposits in a single submarine fan system. Within the Tesnus, six fan-related sedimentary facies are recognized: (I) amalgamated sandstone without vertical thickness trends; (II) amalgamated sandstone;with thinning-upward trends; (III) massive matrix-rich sandstone; (IV) interbedded sandstone and shale; (V) chaotic sandstone and shale; and (VI) black mudrock and chert. The arrangement of sedimentary facies, the nature of facies contacts, and sandstone geometries differ significantly for braided- versus meandering-channel deposits. Sheet-like braided channel deposits commonly exhibit a more random facies ordering and abrupt facies transitions, whereas pod-shaped meandering channel deposits commonly possess a more orderly arrangement of facies (from base to top, Facies I–VI in sequential order) with gradual facies transitions. The aforementioned differences in channel deposit characteristics are believed due primarily to variations in the migrational history of the braided (abandonment and rapid shifting) versus meandering (gradual erosion and migration) channel networks.
Published Version
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