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The AAPG/Datapages Combined Publications Database

AAPG Special Volumes

Abstract


Pub. Id: A045 (1977)

First Page: 93

Last Page: 110

Book Title: SG 4: Reefs and Related Carbonates--Ecology and Sedimentology

Article/Chapter: Cenozoic Reef Systems of Caribbean--Prospects for Paleoecologic Synthesis: Modern and Ancient Reefs

Subject Group: Reservoirs--Carbonates

Spec. Pub. Type: Studies in Geology

Pub. Year: 1977

Author(s): Stanley H. Frost (2)

Abstract:

Paleoecologic reconstruction of the abundant Cenozoic fossil record of Caribbean reefs is basically dependent on uniformitarian comparisons with the biologic and geologic systems forming modern reefs. Much of the present-day coral-reef food web, however, has no mineralized skeletal parts and therefore has a low preservation potential. Detailed direct methods of reconstructing ancient reef systems must depend largely on analysis of the abundance and distribution of organisms which have hard skeletons.

The most useful models for reconstructing the ecology of Caribbean Paleocene-Oligocene reefs are those of the modern Indo-Pacific biotic province, because a substantial part of the Indo-Pacific reef biota descended from lineages which were cosmopolitan during the Paleogene. Because of the mixed cosmopolitan and provincial faunal makeup of early Miocene reef biotas in the Caribbean, uniformitarian comparisons of their ecology with that of modern-day descendants are more complicated than for Paleogene assemblages.

Caribbean middle Miocene to Pliocene reef assemblages became increasingly provincial with the extinction of many remnant Paleogene lineages of large forams, the progressive disappearance of cosmopolitan Indo-Pacific lineages of reef-building corals, and the evolution of modern species of mollusks and reef-building corals. Major changes in the ecologic distribution and abundance of key reef biota occurred in the late Neogene and Pleistocene.

In order to evaluate effectively how much of ancient reef ecosystems can be reconstructed by comparison with modern reefs, it is necessary to take into account not only the proportion of skeleton-bearing groups at each trophic level, but also the actual importance of each group in terms of standing-crop biomass and contribution to the skeletal record of benthic biota. The potential skeletal record of standing-crop biomass is poorest for benthic plants (producers) in all reef habitats. The proportionate paucity of identifiable skeletal material from the producers is therefore multiplied many times in the resultant accretionary skeletal record because their productivity rates are so much higher than consumers on the reefs.

Major conclusions on the ecology of middle Eocene through Pleistocene fossil reefs are: (1) the capacity of Paleogene framework biota to construct and maintain reef structures reached a peak during the Oligocene; (2) reef-framework biota experienced a profound reduction in diversity in the earliest Miocene, with resulting change in the types and abundance of reef structures formed; and (3) the vigor and luxuriance of framework biota appear to have increased throughout the late Miocene and Pliocene.

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