Morphometric Expression of Carbonate Factory Response to Gradients Across a Regional Oceanographic Energy Transition: an Example from the Bahamas-Caicos Archipelago

Abstract:

Carbonate depositional systems are finely tuned recorders of subtle changes in relative sea-level and environmental variability. Recently available high-resolution remote sensing elevation data across the Bahamas-Caicos (B-C) archipelago reveal carbonate geomorphic and facies distributions that enhance previous understanding of changes in paleo-sea level, sediment accumulation, factory type, and diagenesis across the Last Interglacial (LIG) highstand. Uniquely preserved paleogeomorphology in carbonate surface topography provides a spectacular lens for investigating the response of the carbonate factory and surface processes to gradients in waves, currents, and winds across a regional oceanographic energy transition. Semi-automated, machine assisted methods for mapping and quantifying the morphometric expression of strandplains, reefs, tidal bars, polygonal bars, lagoons, tidal flats/channels, and aeolian dune complexes facilitates compilation and synthesis of carbonate paleogeomorphological sea-scapes across unprecedented scale in extraordinary detail.

Pleistocene morphometrics were extracted from high resolution LiDAR and SAR sourced digital elevation models on over 500 carbonate islands in the B-C archipelago spanning approximately 6 degrees of latitude and 9 degrees of longitude. Strandplain facies proportions decrease from over 30% of the total mapped area on Atlantic facing outboard islands to less than 5% on westernmost, inboard islands. The aerial extent and elevation of aeolian dune complexes shows a similar systematic decrease from east to west across the archipelago. Conversely, the westernmost, more protected islands in the B-C system consist of higher proportions of fossilized polygonal and tidal bars. Tidal flat and tidal channel morphometric patterns appear to be less systematic and largely influenced by local energy shadow effects. The archipelago wide morpho-statistics reported here are a foundational element of a more complete, system wide depositional model that will result in improved reliability of carbonate facies predictions that are more closely tuned to the influence of regional depositional energy gradients.