Last Interglacial changes in sea level on Aldabra, western Indian Ocean

Abstract

The Pleistocene limestones on the island of Aldabra in the western Indian Ocean preserve a detailed record of the Last Interglacial interval. Sedimentological analysis has revealed that this interval, formerly regarded as reflecting rapid sea‐level rise, during global warming, followed by a more gradual fall towards the low sea level of the Last Glacial Maximum, in fact shows much greater variation. Although data do not support an accurate chronology, there is evidence that reversals in sea‐level trend caused both pauses in deposition and concurrent erosion during sea‐level rise, and both stillstands and erosion during sea‐level fall. Data include sea‐level related variations in coral morphology, discontinuities and boundaries within depositional sequences, and changes in biofacies. These may explain inconsistencies in the radiometric ages of deposits within the unit, but question the nature of the interglacial cycle, the mechanisms driving it and, in particular, whether comparable variation occurred elsewhere.

DNA- and RNA-based bacterial communities and geochemical zonation under changing sediment porewater dynamics on the Aldabra Atoll

“…In 2012, the lagoons’ sediment types and benthic cover were determined using remote sensing and ground reference points for spatial models 22 . The Pleistocene limestone basement was described in detail by Braithwaite 23 and the biota, including the giant tortoises 24 and (macro-)biota of the soft sediments 25 , have received some attention. The most recent studies on microbial communities were performed 30–40 years ago.…”

Last Interglacial sea-level proxies in East Africa and the Western Indian Ocean

“…In-situ samples from the upper coral terrace were collected and returned an average U-Series Alpha-spectrometry age of 127 ± 18 ka (TH72-001-001 to TH72-008-001, WALIS ID# 591; Table 4) (Thomson and Walton, 1972). Based on the chronological limit provided, a PRSL of +8.5 ± 1.1 m at 127 ± 18 ka was extracted for the 8 m coral terrace (Braithwaite, 2020).…”