Epikarst estuary response to hydroclimate change remains poorly understood, despite the well-studied link between climate and karst groundwater aquifers. The influence of sea-level rise and coastal geomorphic change on these estuaries obscures climate signals, thus requiring careful development of paleoenvironmental histories to interpret the paleoclimate archives. We used foraminifera assemblages, carbon stable isotope ratios (δ13C) and carbon:nitrogen (C:N) mass ratios of organic matter in sediment cores to infer environmental changes over the past 5300 years in Celestun Lagoon, Yucatan, Mexico. Specimens (> 125 µm) from modern core top sediments revealed three assemblages: (1) a brackish mangrove assemblage of agglutinated
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Middle to late Holocene paleolimnology of a sinkhole lake in the northern Bahamas and its linkage to regional climate variability
Sinkholes develop on carbonate landscapes when caves collapse and can subsequently become lake-like environments if they are flooded by local groundwater. Sediment cores retrieved from sinkholes have yielded high-resolution reconstructions of past environmental change, hydroclimate, and hurricane activity. However, our understanding of the internal sedimentary processes of these systems remains incomplete. Here, we use a multiproxy approach including sedimentology (stratigraphy, coarse-grained particle density, bulk organic matter content), micropaleontology (ostracods), and geochemistry (δ13C and δ2H on n-alkanoic acids) to reconstruct evidence for paleolimnology and regional hydroclimate from a continuous stratigraphic record (Emerald Pond sinkhole) in the northern Bahamas that spans the middle to late Holocene. Basal peat at 8.9 m below modern sea level documents the maximum sea-level position at ~ 8200 cal. yr BP. Subsequent upward vertical migration of the local aquifer caused by regional sea-level rise promoted carbonate-marl deposition from ~ 8300 to 1700 cal. yr BP. A shift in coarse particle deposition and ostracods at 5500 cal. yr BP suggests some environmental change, which may be related to one or multiple internal or external drivers. Sapropel deposition from ~ 1700 to 1300 cal. yr BP indicates a fundamental change in limnology to promote increased organic matter preservation, perhaps related to the regional cooling during the Dark Ages Cold Period. We find δ2H28 values are largely invariant from 7700 to 6150 cal. yr BP suggesting a generally stable hydroclimate (mean − 133‰, 1σ = 5‰). The shift to more depleted values (− 156‰, 1σ = 19‰) at ~ 6000–4800 cal. yr BP may be linked to a weakened (eastern displaced) North Atlantic Subtropical High. Nevertheless, additional local hydroclimate records are needed to better disentangle uncertainties from either internal or external influences on the resultant measurements.
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- Award ID(s):
- 1703087
- NSF-PAR ID:
- 10493037
- Publisher / Repository:
- Springer
- Date Published:
- Journal Name:
- Journal of Paleolimnology
- Volume:
- 70
- Issue:
- 4
- ISSN:
- 0921-2728
- Page Range / eLocation ID:
- 265 to 291
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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