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Mylroie, J.E., 2018. Superstorms: Comments on Bahamian fenestrae and boulder evidence from the Last Interglacial. Sea level during the last interglacial (Marine Isotope Substage 5e [MIS 5e]) was ∼6 m above present, interpreted to represent a warmer climate, with increased storm intensity and storm frequency. Two hypotheses have been advanced to demonstrate an increase in storm intensity during MIS 5e. The first considers fenestrae in eolian calcarenites at elevations up to 43 m in the Bahama Archipelago to be evidence of superstorm washover. Additional observations include rip-up clasts and loss of bedform and root structures as a result of wave scour. Such an event should produce a tempestite with a wide-ranging footprint, but none exists above 10 m. This paper argues that the fenestrae are rainfall slurries, rip-up clasts are weathering products of calcarenite protosol development, and bed-form and root structure absence or presence reflects transgressive-phase vs. regressive-phase eolian formation, respectively. In the second case, a 2-km section of the coast of Eleuthera Island contains boulders proposed to have been tossed upward onto the land by superstorm waves, creating an age inversion of older boulders lying on younger rock. These boulders are now karrentisch and rest on pedestals produced by denudation. To emplace them would require extreme energies, but other interpretations such as fossil tower karst and boulders rolling downslope remain viable alternatives. The proposed chronology of boulder emplacement at the end of MIS 5e conflicts with the field evidence of a terra rossa paleosol separating the pedestals and the boulders. A recent paper has argued that normal hurricane activity could have emplaced the boulders. Both of these interpretations fail to explain the lack of similar-sized boulders elsewhere in the Bahama Archipelago. The failure to account for past coastline configuration, cave development in the boulders, and post-MIS 5e boulder denudation makes both boulder analyses incorrect, as discussed herein. [ABSTRACT FROM AUTHOR]

Reports on sea-level changes at the end of the last interglacial according to Bahamian geologic records. What was the major topic of the article; Problems in understanding Bahamian geology; How are caves different to notches; Preservation of coral reefs; Material for reference available.

The majority of limestone islands are made of eogenetic carbonate rock, with intrinsic high porosity and permeability. The freshwater lenses of small islands are dominated by diffuse flow regimes as the island perimeter is everywhere close to the meteoric catchment of the island interior. This flow regime produces flank margin caves at the lens margin, where dissolution is enhanced by mixing corrosion, superposition of organic decay horizons and higher flow velocities as the lens thins. The lens interior develops touching-vug flow systems that result in enhanced permeability and lens thinning over time. As islands become larger, the area (meteoric catchment) goes up by the square, but the island perimeter (discharge zone) goes up linearly; diffuse flow becomes inefficient; conduit flow develops to produce traditional epigenic cave systems that discharge the freshwater lens by specific turbulent flow routes, which in turn are fed by diffuse flow in the island interior. Locally, diffuse flow to the island perimeter continues in coastal proximal areas between major conduit flow routes to produce flank margin caves. The Bahamian Archipelago represents a case history in which tectonics is limited, the rocks are entirely eogenetic and the diffuse to conduit flow transition is demonstrated. [ABSTRACT FROM AUTHOR]