Late Quaternary Mississippi River Incised Valley Fill: Transgressive Depositional Packages

A series of USACE atlas quadrangles and dee pborings from the USGS and LGS with radiocarbon dated peats were used to construct several regional crosssections and paleogeographic reconstructions. Late Pleistocene glaciation and consequent lowered sea leve lresulted in reentrenchment of the Mississippi River incised valley. Meltwater floods from proglacial lakes incised into older deposits followed by braided fluvial (substratum) aggradation due to reduced carrying capacity after floods followed by meandering fluvial(topstratum aggradation as fluvial gradients and discharge decreased. Rapidly rising sea level prevented development of shelf phase deltas prior to~10ka. Attenuated rates of sea level rise and periodic avulsions led to development and subsequent abandonment of several shelf phase deltas and barrier island arcs as well as gradual encroachment of the top stratum up the alluvial valley as aggradational depositon filled available accommodation space