50 Geomorphic Evolution of River Corridors in the Eastern United States from the Pleistocene to the Anthropocene (Posters)

Sunday, 19 March 2023
8:00 AM - 12:00 PM
Grand Ballroom A–D

EXAMINING 17,000 YEARS OF SEDIMENTATION AND ORGANIC ACCUMULATION IN A SMALL UPLAND STREAM CORRIDOR IN NORTHEASTERN CONNECTICUT

Paper number: 50-8
Program: Theme Sessions
Time: 8:00 AM – 12:00 PM

Authors

Abstract

River corridors in the northeastern US are often punctuated with wetlands, ponds and lakes due to the legacy of glacial deposits in the region. These local sedimentary basins have the potential to preserve records of post-glacial and Holocene landscape change, as well as anthropogenic processes more recently. In this study, we present a sediment record extending back to the late-Pleistocene for Codfish Falls wetland, a mid-watershed post glacial lake that transitioned to a wetland over the Holocene, which for the last 40 years has alternated between having a stream channel and being flooded due to beavers. The site is located within the Fenton River watershed in eastern Connecticut on Fishers Brook, a small ~5.2 km2 tributary of the Fenton. Two sediment cores were obtained using vibracoring methods. Core 1 (CFW-1) was collected close to the center of the wetland, recovering 450 cm of sediment, and core 2 (CFW-2) was collected upstream of CFW-1, closer to the wetland edge and adjacent forest hillslopes, recovering 254 cm. The cores were opened, described, and sampled in 3 cm increments. They were analyzed using portable X-ray fluorescence (pXRF) and loss-on-ignition (LOI) to measure organic content and concentrations of metals such as Fe, Pb, Cu, Mn, Zn, Ti, Al, and Ni to better understand sedimentation and patterns of geochemistry at the sites. Overall stratigraphy is consistent with a post-glacial pond gradually transitioning to shallower water and organic accumulation associated with a wetland through time. Pine needle fibers found within fine-grained glacial clay at ~430 cm depth in CFW-1 were radiocarbon dated, resulting in a calibrated age of ~17,335 cal yr BP. This date can likely be associated with the introduction of coniferous trees in the region. Other than the gradual shallowing of water at the site due to sediment infilling and organic accumulation, there are no obvious signs of water level fluctuations through time or sedimentological changes such as sand layers due to floods. Overall, we interpret that the long term record presented in CFW-1 may be typical for other wetlands and ponds that punctuate fluvial systems in the region and holds great potential for studying paleoclimatic changes following deglaciation.

Geological Society of America Abstracts with Programs. Vol. 55, No. 2

doi: 10.1130/abs/2023SE-386002

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