LATE PLEISTOCENE TO MIDDLE HOLOCENE ECOLOGICAL SUCCESSION OF THE MID-ATLANTIC PIEDMONT LOWLANDS, LITTLE CONESTOGA CREEK, PA

The Piedmont Province of the Mid-Atlantic region (MAR) underwent dramatic ecological and landscape changes during the last deglaciation and early Holocene. Deglacial warming triggered northward plant dispersal, initiating an ecological succession from boreal to temperate hardwoods. Concurrently, organic-rich, river-wetland corridors expanded throughout the MAR, suggesting substantial changes to valley bottom landscapes. The Pleistocene-Holocene transformation of the MAR can serve as a paleo-analogue for the consequences of global warming in high northern latitudes. While paleoecological records from valley bottom wetlands are rare, recently discovered river-wetland corridors buried by sediment trapped upstream of colonial mill dams along the Little Conestoga Creek (LLC) provide continuous stratigraphic sequences of Holocene sediments, preserving paleoenvironmental proxies. Here, we present the preliminary Late Pleistocene to Middle Holocene paleoenvironmental reconstruction of the Piedmont Lowlands of Pennsylvania through an analysis of fossil pollen from stratigraphic profiles collected during backhoe trenching along the LCC in 2023. Bayesian age-depth models using 15 radiocarbon dates provide strong chronological control for the pollen record. Preliminary pollen analysis captures a Pinus- Picea -Abies dominated boreal environment during the Younger Dryas, that then transitioned to Quercus-hardwood forests by around 8.2 ka. Around 7.7 ka, Pinus had become the dominant upland tree species and valley bottom wetlands had become fully established. The Pleistocene-Holocene pollen records document the development of Holocene MAR valley bottoms, a potential analogue for the “greening” of high latitudes.