Mapping bathymetry and depositional facies on Great Bahama Bank

Abstract

Satellite imagery and an extensive set of water-depth measurements have been used to map and critically evaluate the magnitude and patterns of bathymetry across Great Bahama Bank. Descriptions of previously collected sediment samples were combined with satellite imagery to map and refine the interpreted distribution of surficial carbonate sediments (depositional facies). Data reveal that 60% of Great Bahama Bank lies in 5 m or less of water. The deep portion occurs mainly in a generally east-west trending area in the southern portion of the platform. The re-evaluation of the facies reveals that Great Bahama Bank is essentially a very grainy platform with muddier accumulations primarily in the lee of Andros Island. This area of Great Bahama Bank also experiences currents related to an excursion of the Florida Current onto the platform top; possibly enhancing sediment mud production through the generation of whitings. Sediment equivalents to mudstones, wackestones and mud-rich packstones cover 8%, 5% and 14%, respectively, of the platform top, whereas sediment equivalents to mud-poor packstones, grainstones and rudstones account for 20%, 45% and 3% of the surface area. Boundstones (reefs) were not specifically mapped in this study due to the resolution of the mapping. There is a poor relationship between the occurrence of the depositional texture and water depth, in that the grainier sediment types are abundant across the full range of water depths. The most abrupt lateral facies changes portrayed on the facies maps are observed leeward of islands, areas which also hold the highest diversity in facies type. The majority of the islands on the platform align with the north-west/south-east strike of the platform margin and these islands, in turn, exert control on the shape and orientation of facies belts that develop in proximity to them. For this reason, regions of the platform that contain principal islands host facies belts that align with the principal axis of the platform, whereas for regions lacking islands, the facies belts adopt an eastwest trend consistent with prevailing winds and currents. There is a clear trend that the wide southern portion of the platform hosts the most continuous expanses of grain-rich sediments.

Revisiting the Late Jurassic-Early Cretaceous of the NW South Iberian Basin: new ages and sedimentary environments

“…This is similar to the shallow subtidal lagoon protected by oolitic shoals in the Great Bahama Bank in which mud and pellet facies-belts are complexly distributed (e.g. Purdy, 1963;Halley et al, 1983;Reijmer et al, 2009;Harris et al, 2015). In fact, in the lagoon of the Great Bahama Bank the percentage of mud increases towards the coast of Andros Island (e.g.…”

“…Wilkinson and Drummond, 2004;Suarez-Gonzalez et al, 2015), as it has been reported in numerous modern systems, such as Bahamas (e.g. Bathurst, 1975;Reijmer et al, 2009;Kaczmareck et al, 2010;Harris et al, 2015), Persian Gulf (e.g. Wagner and Van der Togt, 1973;Wilkinson and Drummond, 2004), Antigua (e.g.…”

“…In fact, in the lagoon of the Great Bahama Bank the percentage of mud increases towards the coast of Andros Island (e.g. Bathurst, 1975;Kaczmarek et al, 2010;Harris et al, 2015), which according to Bathurst (1976), could be related to freshwater inputs from the swamps and channels of Andros Island into the areas next to the coast. Similarly, the distribution of the peloidal packstone facies and the mudstone facies in the facies subassociation D1 could be related with freshwater inputs into the carbonate platform, as suggested by the fact that this facies subassociation overlies sandstone beds interpreted as the result of continental siliciclastic discharges (see sandstone facies association C).…”

Morphometric patterns in Modern carbonate platforms can be applied to the ancient rock record: Similarities between Modern Alacranes Reef and Upper Palaeozoic platforms of the Barents Sea

“…Following the protocol of Purkis et al (2014a) and Harris et al (2014), the slices were analysed using eCognition (v. 8.9, Trimble Inc.). By applying textural and edge-detection routines, refined by manual-editing, the polygonal buildup -ridges‖ and intra-buildup -ponds‖ were mapped and exported as GIS vector files for further analysis (Fig.…”

Depositional, diagenetic and stratigraphic aspects of Macaé Group carbonates (Albian): example from an oilfield from Campos Basin

“…These facies, are characterized by enveloped grains, peloids and greater amount of micrite, related to lower energy sites. In terms of depositional energy, these sediments are equivalent to Andros Island rudstones and mud-poor packstones from Harris et al (2015), which were interpreted as deposited in water depths ranging from 5 to 10 feet deep. These interbank regions can be compared to deposits of sandy peloidais sheets of inner platform defined by Spadini (1992), interpreted as the product of variations in depositional energy between the bank crests.…”