Drainage displacement by sea-level fluctuation at the outer margin of the Chesapeake Seaway

Seismic data adjacent to the southern Delmarva Peninsula illustrate four separate Pleistocene lowstand pathways for the ancestral Susquehanna River. Although regional spits have migrated between these pathways, there is no evidence of continuous channel migration between the channel traces. The mechanism for channel shifting was glacio-eustatically controlled, and occurred at time intervals of 10⁵ years. Channel shifting was operative during early regression when fluvial channels were not confined to their previous antecedent lowstand channels and jumped laterally to new locations. During late Pliocene and early Pleistocene lowstands, at least six major rivers drained across the Chesapeake Basin. Time-lagged channel shifts and stream captures have progressively reduced the number of drainways leaving the basin. During the most recent Stage 2 lowstand, only two or possibly three drainways may have crossed the entrance of the Chesapeake Basin. -from Authors