THE STORM IS UP, AND ALL IS ON THE HAZARD: IMPLICATIONS OF EXTREME STORM DEPOSITS IN THE BAHAMAS DURING THE LAST INTERGLACIAL

Across the Bahamas Bank, carbonate eolianites record evidence of extreme storm activity as climate rapidly destabilized toward the end of the last interglacial (MIS 5e). Typically associated with beach facies, fenestral porosity has been observed in MIS 5e eolian deposits on multiple islands, in some cases up to 43 meters above sea-level. We present detailed outcrop descriptions and petrography from eight MIS 5e eolianite localities, separated by over 600 km, on the islands of Eleuthera, San Salvador, and Providenciales. The evidence demonstrates that the eolian fenestrae beds formed as intense storm waves ran over, ran up, and ran out on coastal dunes during the last interglacial.

On northern Eleuthera (Licrish Hill and Airport Junction), lowland dunes were repeatedly run over by storm waves and reworked into storm-beach ridges with abundant tabular, fenestrae-rich beds, and only minor remnants of eolian cross-beds and root structures. At moderate elevations and inland localities (Two Pines and Tarpum Bay, Eleuthera; Watling’s Castle, San Salvador; Turtle Cove, Providenciales), wave run up formed discrete packages of fenestral beds within the dunes, often associated with scour and rip-ups. Within the highest and most distal dune ridges (Annie Bight and Savannah Sound, Eleuthera; Turtle Cove, Providenciales), storm wave energy ran out, leaving thin, discontinuous, fenestral porosity in the seaward-dipping backsets.

Several factors point to a storm wave origin for MIS 5e eolian fenestrae: Eleuthera, San Salvador, and Providenciales are all situated on the Atlantic margin, where they are fully exposed to hurricanes; the fenestrae beds occur in separate horizons, indicating repeated inundation by multiple events; and, the character of fenestral bedding changes with increasing elevation and distance from shore, as does the abundance and geometry of individual fenestral pores. Finally, other workers have also implicated extreme storms during the last interglacial, in the emplacement of massive wave-tossed boulders along the cliffs of north Eleuthera. Taken together, this record of extreme storms in the Bahamas is sobering, and serves as a cautionary tale for the present interglacial.