The Whale Point Formation: A stratigraphic record of high-frequency climate and sea-level fluctuations in the Bahamas during Marine Isotope Stage 5a (ca. 80 ka BP)

Abstract

In this paper, we formally define a series of bioclastic eolianites and protosols exposed on high-energy bank margins throughout the Bahamas archipelago as the Whale Point Formation (WPF). The position of this new lithostratigraphic unit above and seaward of deposits dated to Marine Isotope Stage (MIS) 5e and below Holocene sediments constrains its age to the latest Pleistocene, more precisely to MIS 5a (ca. 88–74 ka BP). This age is further corroborated by amino-acid racemization data calibrated with UTh ages. Based on their sedimentological characteristics, the WPF eolianites are interpreted as landward-advancing dunes decoupled from their source beaches. Relying on the faunal content, the maximum elevation of relative sea level during MIS 5a can be roughly estimated at ca. 9 ± 2 m below the present stand. The WPF includes two phases of eolian deposition separated by an interval of negative sediment budget and pedogenesis. These different facies possibly reflect millennial-scale sea-level and climate instability during MIS 5a, the latter being likely related to shifts in the mean annual position of the intertropical convergence zone and associated rainfall belt.