Characterizing Late Pleistocene and Holocene Incision and Flooding Post-Glacial Southern New England

Kettle ponds represent localized accommodation space for sediment deposition that can be reliably linked to processes following de-glaciation. In river adjacent kettle ponds the depression traps flood-born material, preserving flood frequency and alterations of the fluvial system. This study examines the sedimentary archive to explore the evidence for, and timing of, river incision in Southern New England from the Late Pleistocene into the Holocene. The study used the sedimentary archive preserved in river adjacent kettles and sediment traps located along the Mount Hope River, Willimantic River, Quinebaug River, and Housatonic Rivers, all in Connecticut. Sediment cores were collected for study from each site using a vibracore rig. Cores were analyzed and sampled for organic content, radiocarbon aging, grain size, elemental XRF, and Magnetic Susceptibility. The analyses of each core were also partnered with paleo-flood recurrence estimation utilizing discharges estimated from modern channel geometry. Analysis in all four cores revealed that between 12,000 to 9,000 yr BP there was a change in sedimentation across all sites. Each site showed higher clastic inputs, coarser grain sizes and lower organic content below the transitional period. The sedimentary change exhibited in both organic content and reduced geochemical markers associated with freshly mobilized material. Similar transitions from clastic to organic dominated accumulation have been seen in marshland cores from many regions of New England, having the same signature in river adjacent traps with no re-initiation of routine fluvial derived sedimentation points to a period of incision during this transition which left the kettles abandoned