INFILLED BLUE HOLES ON THE BAHAMA BANKS AS POINT SOURCES FOR WHITING ORIGIN

Blue holes are a type of karst feature that are found ubiquitously across the Bahamian archipelago. Blue holes are primarily formed by progradational collapse initiated in voids at depth; bank margin fractures also form blue holes. Most blue holes are observed on islands, or proximal to the coast in protected lagoons. It is reasonable to assume that blue hole distributions that are found on islands today should represent blue hole distribution across each of their respective banks. These blue holes that are expected to occur beyond islands and protected coastal areas are likely covered by carbonate sediments that were produced on the bank during the Holocene sea-level highstand.

Multiple authors have demonstrated that blue holes are tidally active features, with strong inflow and outflow currents. We hypothesize that sediment-filled blue holes should also be tidally active, such that water should be brought up from depth within the bank. That water is cooler, and because of depth, should contain additional CO₂ compared to bank water. Once this deep-seated water rises to the bank floor, it would degas and warm, therefore driving precipitation of CaCO₃, similar to processes involved in the formation of Bahamian ooids on bank margins.

We hypothesize that this process is the driving force in the formation of whitings. Whitings have been studied extensively over the past 60 years, though no satisfactory model has yet been established. Recently, Morse et al. (2003), proposed a chemical model that necessitates the repeated resuspension of fine grained sediment to form whitings that come from a deep localized source. Additionally, Bustos-Serrano et al. (2009) demonstrated that there are chemical differences between whiting water and bank water, indicating CaCO₃ precipitation in whiting water; roiling of the bottom sediments below the whitings was observed on the Little Bahama Bank. These observations support our hypothesized model of infilled blue holes as the point source for whiting initiation. On-going research is quantifying the expected number of infilled blue holes, identifying these features on the Bahama Banks, and correlating them with whitings.