Based on aerial and surface reconnaissance of shaliow-water reefs and algal ridges throughout the Lesser Antilles and coring of reef-ridge structures on St. Croix, Martinique, Antigua, and Guadeloupe, maior emergent and shallow-water Holocene bioherms are characterized by maps and sections.
On St, Croix:an extensive bank-barrier reef about 13 to 18 m thick is developed on the inner part of the carbonate shelf. Stratigraphically, this reef has a lower Diploria-Montastrea-rubble-sand or bank) facies, formed during middle to late Holocene time, overlain by a shallow-water Acropora palmata facies formed during the past 1,000 yr. In exposed areas, at depths less than 2 m, crustose coralline pavements are presently forming incipient algal ridges on the reef crest. Shoreward of the barrier reef, on pre-extisting benches at depths of 3 to 10 m, algal ridges had developed from 5000 to 2000 ybp. The developing barrier reef has since blocked wave action from the bench algal ridges, and many are now degenerating.
This same pattern occurs on the windward sides of many Lesser Antillean islands v/ith the following variations: 1) where wave energy is generally greater than on St. Croix, an extensive coralline-Millepore crust in the form of mounds or spurs, incipient algal ridges or even well developed algal ridges cap bank-barrier systems; 2) where bank barriers have not blocked inshore bench algal ridges, they remain well developed and active; 3) under some conditions, apparently associated with high energy and turbidity, fleshy algal pavements cap some bank-barrier structures