It long has been known that the depositional strikes of some facies variables in ancient fluvial regimes are generally perpendicular to the inferred paleoslope. We propose that this is an effective criterion for selecting facies components whose regional distributions were primarily slope induced. A statistical model based on the postulated geometric relation between the paleocurrent pattern and the regional facies trends provides a means of identifying the trend components that were controlled by the depositional slope.

On the basis of 134 measured sections in the Permo-Carboniferous Dunkard Group, paleoslope response components of 5 facies variables were selected using this model. Examination of these trends in conjunction with crossbed readings made at 389 localities reveals (1) a high concentration of clastics on the southeast, consisting primarily of thick belt sandstones (subgraywackes) and red mudstones, (2) a northern drainage outlet characterized by abundant freshwater limestone, coal, sheet sandstone, and gray-green shales, and (3) a second drainage basin to the west with sheet sandstones, red mudstones, and few limestones or coals. Analysis of the slope-induced facies trends indicates that sandstone geometry and distribution were controlled by the configuration of the paleoslope whereas the formation of limestone, coal, red mudstone, and nonred shale depended primarily on the relative positions of the groundwater table and the depositional surface. The Dunkard Group was deposited on a northward to westward sloping alluvial plain from which distributaries emptied into seas on the northeast and southwest of the present Dunkard basin.

End_of_Article - Last_Page 349------------