Abstract: Ooid Sand-Shoal Facies, Joulters Cays, Great Bahama Bank
During sea-level rise in the past 5,000 years, an ooid sand shoal formed in the 450 sq km Joulters Cays area on the margin of Great Bahama Bank. Present depositional environments include the shelf, active ooid-sand shoal, island, stabilized sand flat, tidal channel, and platform interior. Coring has documented six facies: (1) skeletal grainstone, with a shelf exposure; (2) ooid grainstone, exposed on active ooid sand shoals, partly beach and island dune, of ooid formation; (3) ooid grainstone and packstone, exposed on shallow, stabilized-sand flat, developed by bankward transport from active shoal; (4) fine-peloid packstone and grainstone, exposed on platform interior, interpreted as open circulation deposition; (5) pellet wackestone and packstone, deposited under conditi ns of low-energy, restricted circulation; and (6) lithoclast packstone, deposited during transgression over Pleistocene limestone.
The sand shoal consists of lithoclast packstone and pellet wackestone and packstone at the base, overlain by fine-peloid packstone and grainstone, and capped by ooid grainstone and packstone. These laterally continuous facies show a general increase in grain size and percentage of sands, and more grain-supported depositional texture near the top of the sequence. Ooid grainstone only fringes the sand shoal on its eastern and northeastern windward margins. The facies are similar to those in shoaling oolite cycles common in Jurassic and Early Carboniferous strata.
AAPG Search and Discovery Article #90961©1978 AAPG Annual Convention and Exhibition, Oklahoma City, Oklahoma