MARINE ISOTOPE STAGE 5E: A NORMAL OR AN EXTREME INTERGLACIAL? NEW SEDIMENTOLOGICAL EVIDENCE FROM SHALLOW-WATER CARBONATES FROM THE SE BAHAMAS

New data from three southern Bahamian islands show that the last-interglacial (MIS 5e) sea level was characterized by one single highstand that peaked at +11 m above modern datum in the middle of this period, and that the late MIS 5e regression was gradual, and not rapid as commonly assessed.

Fossil reefal and coastal deposits of MIS 5e age are widespread on the tectonically stable islands of Mayaguana, Great Inagua and Crooked (SE Bahamas). An approach including physical stratigraphy, sedimentology, petrography, amino-acid racemization analyses, and U-Th dating was used to investigate these deposits.

The west coast of Mayaguana shows an extensive, 4 m-high, coral-reef terrace including a D. strigosa-A. palmata facies at the base and an A. cervicornis facies at the top. At Devil’s Point, on Great Inagua, a similar terrace containing numerous encrusting corals is capped by bioturbated rudstone rich in coral and mollusk fragments. A large oolitic eolian ridge along the north coast of Crooked Island shows a fossil cliff and a tidal notch at +11 m above modern sea level (msl) that is filled by voluminous cross-bedded beach sediments. Along the SW coast of Great Inagua, low cliffs expose the anatomy of laterally juxtaposed, southward-prograding ridges where beach facies gradually falls from elevations of about +3 m above msl in the northern ridges to about 0.5 m above msl in the southernmost one. The ages of all these deposits range between 130 and 117 ka BP corresponding to MIS 5e.

The D. strigosa-A. palmata facies in Mayaguana and Great Inagua, and the oolitic eolianite in Crooked were likely formed during the early part of MIS 5e when sea level was about +3 m above modern datum. The overlying A. cervicornis facies and the bioturbated rudstone correspond to an important rise of the sea to the elevation of +11 m (tidal notch on Crooked) in the middle part of MIS 5e. The voluminous beach deposits filling the notch relate to the regressive phase of this eustatic episode. Finally, the progressive lowering of the beach facies observed in the Great Inagua ridges shows that the late MIS 5e regression was gradual.