T40 Aeolian Systems in Time and Space (Posters)

Sunday, 22 September 2024
8:00 AM - 5:30 PM
Hall D

THE EOLIAN ORIGIN OF QUATERNARY CALCARENITES, SAN SALVADOR ISLAND, THE BAHAMAS: WHAT WE KNOW SO FAR

Paper number: T40-4
Program: Technical Sessions
Time: 8:00 AM – 5:30 PM

Authors

Abstract

San Salvador Island emerges from a small carbonate platform on the northeastern flank of the Bahamian island chain in the North Atlantic Ocean. Earliest eolian interpretations proposed for Pleistocene and Holocene bioclastic, oolitic calcarenites there were based on thick cross-bed sets, terrestrial gastropod fossils, plant and insect traces, and calcareous crusts and paleosols. Later work documented form and occurrence of eolian ripple, grainfall, and sandflow strata, as recognized by their weathering patterns of ledges and recesses controlled by grain size, packing, and cementing. Early lithification, which preserved internal stratification and dune morphology, was promoted by plant growth and subaerial cement. In Pleistocene eolianites in sea cliffs along eastern, southern, and western margins, subhorizontal topsets of wind-ripple strata grade into foresets of abundant wind-ripple and grainfall strata mixed with scarce sandflow strata. The type and attitude of constituent strata suggest the build-up of coast-parallel eolian dune ridges with lobes that extended further seaward. In Holocene eolianites on North Point peninsula, coppice or shadow dunes, elongated NE-SW, are interpreted from component wind-ripple strata that dip in all compass directions, and from impressions of plants that may have served as sand traps and dune anchors. A build-up of mature eolian dome dunes is inferred from abundant wind-ripple and grainfall laminae, scarce sandflow beds, present-day mound-swale landscape, and 360o dip-directions of wind-ripple strata, dome slopes, and reactivation surfaces. Wind-ripple sedimentation on dome surfaces was interrupted periodically by plant growth and calcareous crusts. Some dome dunes were modified by wind into elongate sand lobes, that were oriented normal to the coast and that advanced westward short distances in the Trade Wind during Holocene time. The shape of the lobe-like calcarenite bodies is preserved in the lobate contour of wind-ripple laminae. Adhesion ripples grew in episodes of rain during Pleistocene and Holocene time on San Salvador, migrated and climbed northeast into Trade Wind, and deposited pseudo-crosslaminae that dip southwest.

Geological Society of America Abstracts with Programs. Vol. 56, No. 5

doi: 10.1130/abs/2024AM-405540

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