Upstream controls on incised-valley dimensions and fill: Examples from the Upper Mississippian Mauch Chunk Group, Central Appalachian Basin, USA

Abstract

Subsurface mapping and facies and architectural element analysis on outcrop, combined with published detrital zircon geochronology and sandstone petrography, are used to reconstruct a source to sink system for two incised-valley fills in the Upper Mississippian Mauch Chunk Group. The lower Stony Gap incised valley is relatively broad and filled with quartzarenite fluvial facies consisting of downstream accreting elements with minimum thicknesses of 6m; cross-sets within elements average 62.5cm thick. The lower Princeton incised valley is relatively narrow and filled with sublitharenite fluvial facies consisting of channel elements that range in thickness from 0.25 to 3.6m; cross-sets within elements average 35cm thick.Quantitative estimates of drainage areas, using regional hydraulic geometry curves for comparable climatic settings, are consistent with order-of-magnitude differences for the lower Stony Gap Sandstone (>700,000km2) and the lower Princeton Formation (<100,000km2). Statistical analysis of the detrital zircon age data reveal that the Stony Gap and Princeton sample populations are not the same and were derived, at least in part, from provenances of different age. Drainage areas are consistent with detrital zircon geochronology and petrographic data and suggest that the lower Stony Gap fluvial sandstone was derived from distal, northern and northwestern cratonic sources including, uniquely, the Archean Superior Province and Proterozoic Penokean-Yavapai-Mazatal provinces, possibly through recycling from older sedimentary rocks. Sediment was dispersed into a NE-SW-oriented, axial drainage system. Inferred channel depths and drainage areas of the lower Stony Gap Sandstone are comparable to the modern Brahmaputra River. In contrast, the younger lower Princeton fluvial sandstone was derived from proximal tectonic highland sources along the eastern margin of the Appalachian Basin that included uplifted older sedimentary rocks and accreted island arc terranes. Sediment was dispersed into a transverse drainage system that was deflected by the existent foreland-basin topography into an axial drainage which is preserved in the study area. Drainage area estimates for the Lower Pennsylvanian Corbin Member in the Appalachian Basin follow the same scaling relationship as the lower Stony Gap Sandstone and lower Princeton Formation incised valleys, where dimensions of incised valleys and their internal fill elements scale to the size of their drainage areas. This study has demonstrated that valley dimensions derived from field and subsurface mapping can be used in conjunction with petrographic data and detrital zircon age spectra to constrain drainage basin area and location, at least to a first order.