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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Late-Holocene hydroclimate inferences for the northern Great Basin from Little Lake, Elko County, Nevada, USA
Prominent lunette dunes 500e800 m long, 50e80 m wide, and up to 5 m tall are present on the floor of
the Independence Valley in northeast Nevada, USA. These dunes border the downwind margins of circular
playas at the end of a drainage descending from the East Humboldt Mountains, which terminates in
an ephemeral water body named Little Lake. Gastropod shells from the Little Lake playa yield radiocarbon
ages of ~400 cal yr BP, after correction for a hard-water effect. A similar age was obtained for
shells from the crest of one of the lunettes. Deeper sediment in this lunette yielded shell ages clustering
around 600 cal yr BP. This pattern suggests two intervals of relatively persistent water at Little Lake, both
of which ended with lake desiccation and deflation of sediment and shells to the adjacent lunette. Shells
from the crest of another lunette yielded radiocarbon ages between 3800 and 1750 cal yr BP. This dune,
therefore, is considerably older and accumulated over a much longer stretch of time. Using the Global
Surface Water Explorer, years between 1984 and 2018 were identified in which Little Lake contained
water in most of the available summer imagery. These years form three clusters: 1984e1987, 1997e2000,
and 2017e2018. Snow water equivalent (SWE) is greater in the mountains, snow makes up a greater
percent of total annual precipitation, and Palmer Drought Severity Index is more positive in this region,
in years when water is present in Little Lake compared with those in which the lake remains dry. Values
of the PDO are also higher in years when Little Lake holds water. Although the hydrology of Little Lake
may be influenced to an unknown degree by upstream water diversions, this overall pattern implies that
the lake and its associated lunettes are a sensitive recorder of late Holocene hydroclimate variability in
the northern Great Basin.
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- Award ID(s):
- 1702975
- NSF-PAR ID:
- 10199003
- Date Published:
- Journal Name:
- Quaternary science reviews
- Volume:
- 244
- ISSN:
- 0277-3791
- Page Range / eLocation ID:
- 106497
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1016/j.quascirev.2020.106497
