NEW AGE CONSTRAINTS ON RELICT PERIGLACIAL LANDFORMS IN THE CONNECTICUT RIVER VALLEY

The Connecticut landscape faced rapid geomorphological transformation in response to deglaciation and post-glacial climate change 18,000 to 12,000 years ago. One distinctive aspect of this transformation was the formation and eventual collapse of periglacial landforms between 15,500 and 13,500 BP, which are often found within the lake bottom sediments of drained Glacial Lake Hitchcock. Paired with a permafrost conducive climate, the fine lakebed sediments likely made for favorable conditions to form pingos, palsas, and lithalsas. Today, these relict landforms are abundantly observed across the Hartford Basin in high resolution topographic data as clusters of semi-circular depressions 10-30 m in diameter. To build a stronger stratigraphic interpretation of these relict periglacial landforms and their variability, four sediment vibra-cores were collected from three circular depressions in Keney Park in central Connecticut. In this location, nearby relict eolian dunes may have been active at the same time as the periglacial activity, and contributed to the observed depositional record. Sediment cores were analyzed for organic content (LOI), elemental analysis (pXRF), grain size, radiocarbon dating, and the presence of diatoms and phytoliths. Additionally, ground penetrating radar (GPR) was collected across the depressions to study lateral trends in subsurface stratigraphy. Calibrated radiocarbon dating results from two of the cores span between 13,182 B.P.–14,929 B.P., with the oldest dates being within stratigraphic units believed to be post-collapse. Overall, these ages are consistent with previous regional studies but suggest variability in the localized timing of glacial lake drainage, subsequent lakebed deformation associated with periglacial activity, and collapse of periglacial landforms. Additional details captured in the stratigraphy include the depositional response of anthropogenic impact such as heavy metal accumulation, road erosion, and geochemical signals of agriculture.