T217 From Coastal Lowlands to Shallow Shelf: Environmental Processes of the Coastal Critical Zone through Time and Space

Wednesday, 18 October 2023
8:00 AM - 12:00 PM
303

FILLING THE EARLY OLIGOCENE GAP IN THE RECORD OF CARIBBEAN REEF CORALS

Paper number: T217-10
Program: Technical Sessions
Time: 10:15 AM – 10:30 AM

Authors

Abstract

There is an Early Oligocene gap in the record of reef corals from the Caribbean. Late Eocene corals are recorded from a number of regions in the Caribbean, and these are notably different from the rich fauna of reef-building corals known from the Late Oligocene. A significant faunal turnover event, then, likely occurs sometime during the Late Eocene or Early Oligocene. New data from this important interval has been found in a recent large road cut near Faith’s Pen in central Jamaica that exposes a coral rich succession from the Early Oligocene. A 40+ m section is exposed in this cut with abundant corals and the oldest, distinctly mesophotic coral fauna in the Caribbean. The large benthic foraminiferal fauna represents an outer shelf fauna and indicates that it is Middle Rupelian in age.

At the base of the section is a low carbonate mound with scattered platy and branched corals. Draped over this mound is a 2 m thick, densely packed bed of platy corals. This bed is dominated by Fungophyllia spp. and the plates are all <1 cm thick and each plate is separated by approximately 1 cm of micritic sediment. Platy corals become less common upsection where isolated massive corals (chiefly Antiguastrea cellulosa), in place thickets of phaceloid branching forms (Caulastraea sp.) and thin, ramose branching forms become more dominant.

The fauna recorded from this site is considerably less diverse than that found in shallower water sediments from the Late Oligocene in Jamaica, Puerto Rico and Antigua. While a large part of the fauna is in growth position, the only group of clustered corals that represent a clear coral growth fabric is found in the bed of mesophotic platy corals. This is the earliest demonstrably mesophotic coral fauna in the Caribbean and is dominated by a single species, indicating that diversification in Caribbean deeper water corals occurs later in the Cenozoic. On the whole, the coral species that are most common throughout this section are the same species that dominate reef faunas in the Late Oligocene of the Caribbean. Therefore, the Late Eocene/Oligocene coral turnover appears to have occurred before the formation of this Middle Rupelian mesophotic coral fauna.

Geological Society of America Abstracts with Programs. Vol. 55, No. 6

doi: 10.1130/abs/2023AM-395530

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