Chevron Ridges and Runup Deposits in the Bahamas from Storms Late in Oxygen-Isotope Substage 5e

Abstract

Landward-pointing V-shaped sand ridges several kilometers long are common along the windward margin of the Bahama Islands. Their axes share a northeast–southwest trend. Internally, the ridges contain low-angle oolitic beds with few erosional truncations. Commonly interbedded are tabular, fenestrae-rich beds such as those formed by the sheet flow of water over dry sand. Defined 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 coastlines 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 inland, recording the impact of large waves. Amino acid ratios confirm a correlation of the ridges across the archipelago, while stratigraphy, spacing, and cross-cutting relationships indicate emplacement as sea level fell rapidly from the substage 5e maximum at or above +6 m.

Reliquiae Diluvianae Alter: Last Interglacial Flood Deposits In The Caves Of The West Indies

“…While there are no other published records of storm events at inland sites, there is some evidence of increased wave activity on coastal sites, presumably indicating enhanced storm activity. Hearty et al (1998) interpret a series of coastal sand ridges on the windward margin of several of the Bahama Islands as originating from extreme storms during the last interglacial. 'Megaboulder' (boulders of ~ 10 6 kg) deposits on Eleuthra (Hearty, 1997), suggest unusually intense wave activity at some stage during the last interglacial, which has been attributed to tsunamis or extreme hurricanes.…”

Tsunamis as geomorphic crises: Lessons from the December 26, 2004 tsunami in Lhok Nga, West Banda Aceh (Sumatra, Indonesia)

“…The genesis of these coastal bedrock erosional features is far from being resolved (Felton and Crook, 2003;Nott, 2004). The succession of outsets and insets, especially along the dam of South Lhok Nga, and the enlarged lagoons remind the chevron ridges described in the Bahamas by Hearty et al (1998) and in Australia by Bryant et al (1996), but they are 15 to 30 times smaller in size.…”

Vertebrate community on an ice-age Caribbean island

“…The archipelago features 23 major islands (>50 km 2 ) and many smaller ones that lie on shallow carbonate banks separated by deep water. All exposed bedrock is Quaternary aeolianite and shallow marine limestone; much of the build-up took place as late as Marine Isotope Substage 5e (125 ka) (20)(21)(22). The archipelago stretches 980 km from ∼27°N, 79°W in the northwest to ∼21°N, 71°W in the southeast; it comprises the independent Commonwealth of the Bahamas ("The Bahamas") and the Turks and Caicos Islands, a British protectorate.…”