From the Quaternary of San Salvador Island, Bahamas to the Jurassic of Southern Utah – Eolian Architecture in Calcarenites and Sandstones Compared

Given a steady supply of sand-sized mineral grains and a persistent wind to dislodge and entrain them, eolian ripples and dunes are known to develop in a variety of climatic and tectonic settings worldwide. Eolian sediment, in general, is considered siliciclastic, dominated by quartz-rich sand. On San Salvador Island, Bahamas, mostly lithified Quaternary carbonate deposits exhibit stratification and subaerial features that point to a wind-blown origin. These eolian calcarenites are similar to Jurassic eolian sandstones of southern Utah in grain size, grain texture, and stratification but are inherently paradoxical because of the unequivocal marine origin of constituent ooid and skeletal framework grains. For both suites of rocks, clast size ranges from very fine- to medium-sand; the higher specific gravity of clasts in the San Salvador calcarenites being compensated by intragranular porosity. Ripple, grainflow, and grainfall mechanisms controlled geometry and distribution of corresponding bedding units – wind-ripple, sandflow, and grainfall strata. Sand size, packing, sorting, and grading, and porosity and permeability influenced cementing and weathering patterns of component eolian strata. During accumulation of Quaternary calcareous sand by wind around the small island of San Salvador, marine moisture fostered dune stabilization by vegetation and early subaerial cementation. Consequently, a low ridge-like assembly of small dunes, characterized by thin crossbeds and crossbed-sets, migrated a short distance; whole dune-forms were preserved. Whereas, during deposition of Jurassic eolian sandstones in southern Utah, greater aridity, depositional area, and sediment volume favored the build-up and distant migration of large complex dunes in an extensive sand sea. Late cementation occurred after burial, and the dune system is only partly preserved mainly as thick crossbeds, crossbed-sets, and interdune strata.