Geomorphic Evolution and Heterogeneity of Holocene Carbonate Tidal Sand Shoals

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Geomorphic Evolution and Heterogeneity of Holocene Carbonate Tidal Sand ShoalsGene Rankey, University of KansasThe archive of change on the Earth's surface is contained in its stratigraphic record. Deposits of ooids (spherical concentrically laminated grains) in particular have provided key insights into physical and chemical variability in the ocean over billions of years. On-going research has illustrated how variable bedrock configurations, tides and waves lead to different geometries (tidal deltas, tidal sand ridges, parabolic bars, sigmoidal bars) in tidally dominated oolitic sand shoals that are active today. This study will expand on those insights, exploring the hypothesis that these variable processes impart a distinct and unique stratigraphic record to each shoal geometry. To address these questions and test the hypothesis, this study will utilize high-resolution subbottom geophysical profiling, coring, and age dating from a suite of Holocene Bahamian shoals characterized by different processes and landforms. In comparing the thicknesses, the elevation of the bedrock beneath the shoals, and sedimentologic trends within the shoals, the results of this study will lead to enhanced understanding of evolution of these oolitic systems, and to tidal sand shoals in general. Furthermore, precise age dating of the oolitic sediments will reveal the rates of geomorphic change, information difficult to ascertain in siliciclastic systems. Collectively, these data will provide key insights to better constrain interpretation of the planet's history in response to global change, to predict the distribution and variability of oolitic sedimentary rocks in the subsurface (e.g., in water or hydrocarbon reservoirs), and to understand possible rates of recovery from sand mining. This proposal will fund development of mix of lecture, hands-on lab, and field experiences on ooid shoals for Bahamian and international students, offered by the PI and student for several semesters, at the Island School on Eleuthera Island in The Bahamas.