THE TIMING OF LAURENTIDE ICE SHEET DEGLACIATION AND POSTGLACIAL PALEOENVIRONMENTAL CONDITIONS FROM NUANGOLA LAKE AND NORTH LAKE, LUZERNE COUNTY, PENNSYLVANIA

Sediments from lakes in northeastern Pennsylvania contain continuous archives of Laurentide Ice Sheet (LIS) deglaciation and postglacial environmental conditions. Here, we present multiproxy glacier and paleoenvironmental records from two lakes in Luzerne County that document late Pleistocene climate variability along the LIS southeast margin. Nuangola Lake (41.159º N, 75.974º W, 356 m ASL) and North Lake (41.292º N, 76.144º W, 418 m ASL) are relatively small, shallow (depth < 10 m) glacial lakes located approximately 12 and 30 kilometers north of the Last Glacial Maximum terminal moraine. We collected overlapping sediment cores from both lakes, characterized the sediments via smear-slide mineral analysis, and imaged the cores and measured visible reflectance to estimate sediment chlorophyll-a content. We also measured dry bulk density, organic matter via loss-on-ignition, magnetic susceptibility, biogenic silica, and use radiocarbon dating on terrestrial macrofossils to establish age control. The basal sediments in both lakes consist of laminated to banded very fine-grained (clay) minerogenic sediments with high bulk density, high magnetic susceptibility, and low sediment organic content. We interpret the basal sediments as glaciolacustrine, which reflect the delivery of glacial flour to the lake basins immediately after ice sheet retreat. The transition to the overlying postglacial sediments is gradual and conformable. The postglacial sediments consist of homogeneous fine-grained (clay and silt) silicate mineral and organic sediments with low bulk density, low magnetic susceptibility, and high sediment organic and biogenic silica content. We discuss the sediment records in the context of other regional lacustrine proxy and glacial-geologic records to develop a regional synthesis of LIS deglaciation and postglacial environmental conditions in northeast Pennsylvania.