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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 65 (1981)

Issue: 5. (May)

First Page: 896

Last Page: 897

Title: Reefal Margins of Pliocene-Pleistocene of Great Bahama Bank: ABSTRACT

Author(s): David K. Beach

Article Type: Meeting abstract


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Examination of 16 shallow core borings from the Great Bahama Bank reveals that coral-coralline algal deposits of Pliocene-Pleistocene age line the margins of the bank. These reefal deposits extend up to 5 km bankward from both windward and leeward edges of the platform. Those along leeward margins are framestones and grew in relatively deep water. Those along the windward margins are a mixture of framestone and bafflestone formed in water of various depths probably including low intertidal. A similar assymetric distribution of depositional textures may be indicative of windward versus leeward margins on ancient platforms.

The margins of the bank evolved upward through the Pliocene-Pleistocene. This evolution may be divided into three stages. In stage I, the lowermost, discrete depositional units average 8 m in thickness and contain an abundance of species of corals now extinct, including Stylophora affinis. In stage III, depositional units average 3 m in thickness and corals such as S. affinis are rare or absent. Stage III is marked by accumulation of nonskeletal sands (beach and eolian dune deposits) along inner-bankward parts of the margins. The distribution of reefal sediments was reduced to a narrow belt similar to that of the present. The change from stage I to II is of uniform time, apparently coinciding with the initiation of major Northern Hemisphere glaciation at the beginning of the late Plio ene; that from stage II to III is more variable, occurring from the middle to late Pleistocene.

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