STREAM POWER AND SEDIMENT SUPPLY CONTROLS ON AN ALLUVIAL SEDIMENT ARCHIVE IN THE MID-ATLANTIC REGION

The North Branch of the Susquehanna River traverses incised meanders through the Appalachian Plateaus and Ridge and Valley physiographic provinces of northeastern Pennsylvania. The valley was glaciated downstream to its juncture with the West Branch at Northumberland, and the most recent advance reached downstream as far as Berwick. The bedrock valley meanders and distribution of glacial detritus within the river valley result in significant variations in stream power and sediment texture of the channel perimeter. Unit stream power values calculated for 23 channel cross-sections indicate a stable channel formed by vertical accretion of fine-grained alluvium. Variations in stream power and sediment supply only partly control the distribution of alluvial lithofacies within the Holocene sediment archive. Valley-wide depositional hiatuses and climatically-driven flood episodes are also evident if the stratigraphy is taken apart using the buried soils formed on former floodplain surfaces.