INVESTIGATING SEDIMENTATION AND ABANDONED OXBOW LAKES IN THE NATCHAUG RIVER VALLEY, EASTERN CONNECTICUT

Oxbow lakes can serve as sediment traps within active floodplains, capturing natural and anthropogenic effects on depositional processes. This study investigates sedimentary and geochemical records in two abandoned oxbows within the Natchaug River floodplain in eastern Connecticut to reconstruct its recent evolution and environmental history. Four sediment cores were collected and analyzed for sediment characteristics (layering and grain size), organic content (LOI), elemental composition (pXRF), and radiocarbon dating to identify sedimentation patterns and anthropogenic impacts. Radiocarbon ages at the bottom of the two sampled oxbows and in the adjacent floodplain range from ~960-1490 cal yrs BP, indicating relatively recent deposition in the floodplain and flooding events that allowed for river migration and oxbow formation. Organic content and heavy metal analysis (esp. Pb, Zn, Cu, and As) highlights the gradual infilling of the oxbow since formation and possible contributions from floods, historical agricultural and industrial activity. There was no detectable mercury, indicating that this river system is not subject to levels of contamination often seen in oxbows in the northeast. A coarse-grained layer enriched in iron at depth marks a high-energy environment, emphasizing the oxbow’s capacity to preserve extreme hydrologic events (within the last 900 years).