Chevron ridges and runup deposits in the Bahamas from storms late in oxygen-isotope substage 5e

Landward-pointing V-shaped sand ridges several kilometers long are common a long the windward margin of the Bahama Islands. Their axes share a northeas t-southwest trend. Internally, the ridges contain low-angle oolitic beds wi th few erosional truncations, Commonly interbedded are tabular, fenestrae-r ich beds such as those formed by the sheet flow of water over dry sand. Def ined here as "chevron ridges," these landforms appear to have originated in the rapid remobilization of bank margin ooid bodies by the action of long- period waves from a northeasterly source. Deposits along adjacent coastline s also preserve evidence of the impact of large waves. Reworked eolian sand bodies preserve beach fenestrae and hydraulic scour traces up to +40 m on older ridges. On cliffed coasts, 1000-ton boulders have been thrown well in land, recording the impact of large waves. Amino acid ratios confirm a corr elation of the ridges across the archipelago, while stratigraphy, spacing, and cross-cutting relationships indicate emplacement as sea level fell rapi dly from the substage 5e maximum at or above +6 m. (C) 1998 University of W ashington.