LIDAR DEM BASED MAPPING AND SEDIMENT CORING HIGHLIGHT NEW DETAILS ON PALEO PERIGLACIAL PROCESSES IN CENTRAL CONNECTICUT

The retreat of the Laurentide Ice Sheet left the New England landscape open to many changes, including the formation of glacial lakes such as Glacial Lake Hitchcock. After the draining of Glacial Lake Hitchcock around 15.5 ka, lake bed sediments were exposed to permafrost conditions that allowed for the formation of periglacial landforms such as pingos. Eventually, climate warmed, the ice melted and these pingos collapsed to form circular rimmed depressions. or pingo scars. Previous research on pingo scars in Connecticut highlighted their occurrence in a few select locations on the drained lake bed of Glacial Lake Hitchcock with 14C dates in the range of 15-14 ka. In this contribution, we expand upon this previous research by using high resolution topographic data from LIDAR data to map pingo scar landforms over the entire Connecticut River valley in central Connecticut and present results from a new sediment core collected away from sites cored in the past. Our sediment core is a 2.5 m vibracore collected in a pingo scar in East Windsor, Connecticut. It was analyzed for loss-on-ignition (LOI) and portable X-ray fluorescence (pXRF) to characterize sedimentological and geochemical changes. LOI exhibits a marked increase in organic content near the surface, consistent with the change from varved glacial lake clay at depth to an organic-rich wetland up top. The patterns of Cu and Zn in the pXRF data in the upper 50 cm of the core indicate the variable mobility and absorption of these elements in organic matter. Principal component analysis of the pXRF data generally shows elemental distributions are controlled by main units of the core. 14C dating is in progress on organic material collected in the upper portion of the clay rich unit to constrain the timing of collapse and transition to a wetland. Overall, LiDAR mapping indicates that pingo scars are much more widely distributed across the region than previously appreciated, with great potential for additional coring studies.