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Late Quaternary sedimentation in two phreatic caves in northwestern Florida, USA: the influence of climate variability and cave geometry

By Tyler Scott Winkler


Thick sediments have accumulated in many inland phreatic caves in the Floridian Ocala limestone (USA), but the paleoenvironmental value of these sediments remains unknown. Phreatic cave sediments could provide proxy-based evidence for long-term hydrodynamics of the local aquifer. To test this hypothesis, several sediment cores were collected from two caves: Hole in the Wall Cave (HITW) and Twin Cave in Marianna, Florida (USA). The subsurface stratigraphy in both caves captures snapshots of the deglacial evolution of the Western Floridian aquifer, but radiocarbon dating indicates that a punctuated sediment supply and budget hampers the temporal continuity of the paleoenvironmental records. Sedimentation in both caves is dominated by fine-grained iron and manganese oxide and oxyhydroxide minerals. However, after 5600 calibrated years before present (Cal yrs BP), deposition in HITW switches to fine-grained organic matter, perhaps marking the onset of modern hydrologic conditions. In addition, a 40 cm unit of detrital organic matter deposited over ≈100 years in Twin cave at 13,900 Cal yrs BP is perhaps related to a regional shift towards a warmer and wetter climate during the Bølling-Allerød warming at ≈14,000 Cal yrs BP. If more continuous sedimentary records can be recovered, sediments in inland phreatic caves may produce paleohydrologic records

Topics: Sediment, Karst, Paleoclimate, Hydrology, Cave, Groundwater, Geochemistry
Year: 2017
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Provided by: Texas A&M University

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