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We evaluate the potential occurrence of rapid, millennial-scale sea-level oscillations in the limestone Falmouth Formation from Jamaica. Fossil coral reefs are observed in outcrops of the Falmouth and date back to the Last Interglacial period, or Marine Isotope Stage (MIS) 5e. The stratigraphy, age and elevation of these reefs can be used to constrain the timing and rates of sea-level rise during this warm period of earth’s history. These insights will help us to understand potential rates of sea-level rise as the climate warms in the future, affecting coastal ecosystems and water resources. Across the Caribbean, many exposed MIS 5e reefs were investigated to understand sea level and ice sheet dynamics in a warming world; however, the rates of sea-level change during MIS 5e remain unclear.
In Jamaica, transitions between reef units are sometimes associated with sharp unconformities in vertical exposures. Outcrops in East Rio Bueno feature a clear change in coral taxonomy from in situ Montastraea spp., Siderastrea and Diploria sp. encrusted by coralline algae, next to a repeated succession of Porites furcata, Acropora cervicornis, coralline algae and Porites astreoides, to in situ P. furcata. This sequence is capped by a fining-upwards unit of coral rubble, a laterally-persistent layer of small in situ Siderastrea and a ~1-m thick caprock. Eastward, a layer of primarily Acropora palmata transitions upwards into in situ Montastraea spp., Siderastrea, Colpophyllia natans, Diploria sp. and A. cervicornis. The southwestern coastline features situ A. palmata and/or rubble, and a reduction in algal encrustation upsection, overlain by head corals and a regressive beach unit.
These observations will be paired with radiometric dates of corals to determine if millennial-scale sea-level oscillations occurred as sea-level rose to the MIS 5e highstand, shedding light on the capability of sea-level and ice sheets to respond to global warming on shorter timescales. |