25 Nearshore and Estuarine Research: Dynamics and Future Resiliency in the Coastal Zone II

This session focuses on drivers of change in coastal environments as well as planning for future resiliency in tidal marshes, mudflats, estuaries, and barrier systems, including human activity impacts, sea level rise, & changing sediment supply.

Monday, 23 March 2026
1:30 PM - 5:30 PM
CCC, Room 22/23

Regional Synthesis of Late Quaternary Nearshore Sediments Across Coastal Connecticut

Paper number: 25-7
Program: Technical Sessions
Time: 3:30 PM – 3:50 PM

Authors

Abstract

Coastal Connecticut spans a critical transition zone between terrestrial postglacial landscapes and the offshore depositional environments of Long Island Sound, yet its nearshore environment remains comparatively under-resolved. Here we provide a nearshore and shore-proximal extension to the current framework of the Late Quaternary history of Long Island Sound from high spatial density, horizon-resolved sediment core assemblages captured from the nearshore environment. The dataset (n = 714) comprises subaqueous vibracores (n = 382, maximum water depth of 4 m) and coastal salt marsh push cores (n = 332) collected during the USDA-NRCS Coastal Zone Soil Survey between 2022 and 2024 and provides unique spatial coverage of Late Quaternary sediments from across the nearshore zone. We integrate horizon-scale National Soil Information System (NASIS) descriptions, geochemical and textural analyses, and geospatial analyses, alongside new local radiocarbon (14C) constraints, to explore nearshore sedimentation since the Late Pleistocene. All core horizons (n = 3,569) were manually assigned one of three classifications based on available data and vertical position in the core and collectively record a coherent history characterized by (1) the deposition of glacial and early postglacial sediments, (2) the deposition of Holocene sediment on subaerially exposed topography, and (3) the progressive inundation of the shore-proximal subaerial landscape by rising relative sea levels during the Holocene through present. Every core preserves a part of this history; most commonly, (post-)glacial sediments are preserved beneath more recent coastal sediments with or without preservation of subaerially-exposed Holocene deposits. Consequently, the data record locally and regionally discontinuous surfaces between phases. In some instances, expressions of all three phases are observed within a single core, as in the case of S2023CT001043 (nhorizons = 6, nradiocarbon = 10), a vibracore prototypical of the three-phase regime, taken in Smith Cove, Greenwich, CT, which captures a buried A horizon developed on glacial till (Unit 1, cal. 15.2 to 7.5 ka) beneath a woody, fibric peat (Unit 2, cal. 4.25 to 2.8 ka) beneath a gradually fining estuarine silt loam (Unit 3, cal. 1.3 ka to present). This integrated dataset exposes local and regional patterns across coastal Connecticut and underscores the contextual value of coherent regional vibracore datasets in interpreting postglacial coastal evolution under rising sea levels.

Geological Society of America Abstracts with Programs. Vol. 58, No. 2

doi: 10.1130/abs/2026NE-411469

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