122 D4. Paleoclimatology, Sedimentary, and Historical Studies in Caves and Karst Features

Monday, 23 October 2017
1:30 PM - 5:30 PM
Room 612

EVIDENCE FOR HOLOCENE HYDROCLIMATE VARIABILITY IN THE NORTHERN BAHAMAS (ABACO ISLAND) BASED ON SINKHOLE LAKE SEDIMENT RECORDS

Paper number: 122-4
Program: Technical Sessions
Time: 2:05 PM – 2:20 PM

Authors

Abstract

Rainfall in the tropical North Atlantic is linked to multiple ocean and atmospheric factors whose relative influence on regional rainfall is highly variable (e.g., North Atlantic Subtropical High, Easterlies, El Nino/Southern Oscillation, Intertropical Convergence Zone). In the Northern Bahamas, seasonal intensification of the North Atlantic Subtropical High (NASH) significantly decreases seasonal rainfall as northern islands become increasingly exposed to atmospheric subsidence. Hydroclimate records from lower tropical latitudes suggest the Intertropical Convergence Zone (ITCZ) experienced meridional displacements during the Holocene, which likely influenced rainfall in the lower latitudes. It remains uncertain how displacements in the Hadley Cell, including both the ITCZ and NASH, have impacted rainfall in the Northern Bahamas, but confoundingly, available pollen records suggest little Holocene floral change in the Northern Bahamas (e.g., Andros, Abaco) except during the last millennium. The sediment record in caves and sinkholes can provide an important hydroclimate perspective from carbonate landscapes. On Abaco Island, the low-resolution stratigraphic record from No Man’s Land basin documents a change to a negative water balance from 3300 to 2500 Cal yrs BP, which coincides with evidence for increased aridity from hydroclimate records elsewhere. Also from Abaco Island, a higher-resolution stratigraphic record from Great Cistern Sinkhole documents oscillations in calcite raft deposition from ~7000 to 1000 years ago. A decrease in calcite raft deposition from 3300 to 2500 Cal yrs BP is coincident with aridity documented at No Man’s Land. This suggests that decreased calcite raft deposition in Great Cistern Sinkhole and rainfall on Abaco Island are related. Based on the record from Great Cistern Sinkhole, Abaco Island experienced re-current intervals of drought during the late Holocene, which may be linked to recurrent westward or southward expansion of the NASH.

Geological Society of America Abstracts with Programs. Vol. 49, No. 6

doi: 10.1130/abs/2017AM-306400

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