Luxuriant growths of reef-building corals and associated biota are characteristic of easterly facing margins of the Florida and Bahamas platforms. Along the eastern margins the reef community is most luxuriant and continuous seaward of islands; it is absent or poorly developed where islands are absent. The reef community is absent along almost all the western margins of the platforms and its few occurrences seaward of islands or shoals are small, discontinuous, and without the variety and vitality of the eastern examples.

The reef community favors the eastern margins because wave agitation and circulation of oceanic water that promotes its growth is more intense there than on the western margins. The western margins are unfavorable because water from the platform interiors, warmer and saltier than normal, is moved westward across them by the prevailing easterly winds.

The most luxuriant growths of the reef community are seaward of islands because the islands protect these areas from unfavorable currents. The islands prevent the existence of the normal cross-platform currents that produce bottom-sediment movement (oolitic sands) unfavorable for the reef community. The islands shield areas seaward of them from tidal runoff of platform-interior water that is inimical to the growth of the reef community.

Can these "principles" be applied to ancient reefs?

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