137-8 Late Pleistocene Stratigraphic Architecture in a Bahamian Karst Lake: Facies Associations and Chronology

Session: Joint SGD-SEPM-IAS Focus on the Sedimentary Record of Climate Change

Presenting Author:

Ashlyn Posey

Authors:

Posey, Ashlyn¹, van Hengstum, Pete², Tamalavage, Annie³, Sullivan, Richard⁴, Donnelly, Jeffrey P.⁵, Fall, Patricia⁶, Albury, Nancy A.⁷, Wallace, Elizabeth⁸

Abstract:

Marine Isotope Stages 2 (~29–14 ka) and 3 (~57–29 ka) in the late Pleistocene encompass key climatic intervals, including the Last Glacial Maximum (LGM) and abrupt climate shifts such as Dansgaard-Oeschger (DO) oscillations and Heinrich Events (HE). Hydroclimate in the subtropical North Atlantic is strongly influenced by the position and intensity of the North Atlantic Subtropical High (NASH; also known as the Bermuda High), local convection, and hurricane activity, all of which are poorly constrained in glacial climate states. While DO oscillations are well documented in both high-latitude (e.g., Greenland ice cores) and low-latitude (e.g., Cariaco Basin) archives, the regional expression of Heinrich Events remains spatially variable. It has been previously presented that a terrestrial stratigraphic record from a groundwater-fed, karst sinkhole lake (diameter: 200 m; depth: 55 mbsl) has been recovered from the northern Bahamas (Abaco Island), and the stratigraphic accumulation spanned the last ~55,000 years. Building on this work, we present a pre-Holocene master stratigraphic architecture, chronology and facies analysis that spans 15–55 ka. The stratigraphy reveals that relative sea-level change exerts a primary control on sedimentation, with more detailed facies changes likely driven by local hydroclimate variability. New radiocarbon results improve confidence in the stratigraphic architecture and lend support to refined interpretations of hydroclimate variability throughout the Late Pleistocene in the northern Bahamas. This updated chronology contributes critical new data toward understanding how subtropical climates responded to global climate perturbations during the late Pleistocene.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-8137

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