The Sediment Budget of Great Bahama Bank – Insights From Simulations, Satellites, and Seismic

Sediment production, transport, and accumulation atop and around Great Bahama Bank are rigorously investigating using simulation, satellite, and seismic techniques. Hydrodynamic modeling and sediment transport simulations suggest that fair-weather conditions are primarily responsible for redistributing sediments from their sources and creating the sedimentary facies seen today. Conversely, a single catastrophic storm, such as Category 4 Hurricane Matthew (2016), only winnows mud. This work casts doubt on paleo-storm interpretations based on coarse-grained tempesites and emphasizes the role of fair-weather condition in sculpting the shallow-water carbonate rock record.

The relative sway of fair-weather winds, waves, and tides on total suspended sediment was further investigated using satellite observation in a machine learning framework. Elevated winter winds, particularly during El Niño and in the platform interior, are found to increase suspended sediment on interannual time scales. Too, oscillations in the Lunar Nodal Cycle and the Atlantic Meridional Overturning Circulation are found to modulate suspended sediment on semi-decadal time scales. Notably, wind is the dominate driver of suspended sediment on the leeward margin, while tides, often focused between aeolian islands, are found to be the dominant driver of suspended sediment on the windward margin.

Using these previous methods combined with seismic and literature data, a Late Holocene sediment budget for Great Bahama Bank (GBB) is created. In doing so, cumulative production, export, and accumulation are assessed over a range of cases (low, medium, and high). The budget suggests only medium to high production rates coupled with low to medium accumulation rates yield the surplus or balance, respectively, necessary to account for the observable growth of GBB over the last 6.7 kyr, or since it last flooded. As such, this work intimates that the ability of a carbonate platform to keep up with sea level rise and provide sediment to its adjacent flanks is more tenuous than previously believed.