COMPARATIVE TAPHONOMY OF LATE PLEISTOCENE CORALS IN NORTH-CENTRAL AND SOUTH-EASTERN JAMAICA

Late Pleistocene coral reefs across Jamaica grew in a range of environmental conditions and stressors. This can be observed by comparing the corals in the pure carbonate Falmouth Formation in north-central Jamaica (a fringing reef along a rocky limestone coast) with the siliciclastic-carbonate Port Morant Formation in the southeast of the island (a reef seaward of a prograding delta front).

Following an assessment of paleo-reef zonation at both localities, quantitative analysis was undertaken on a total of 58 coral samples from the crest and backreef zones. Using ImageJ software, the taphonomy of the coral samples (201 slabs) was quantified based on the percentage of sediment occlusion, encrustation, and macroboring. Macroborers and encrusters were also identified by their genus.

Backreef deposits in the Port Morant Fm. are characterized by extensive sediment occlusion, infilling of primary cavities of branching corals by microbialite crust, and thin (≈1mm), patchy calcareous algal encrustation whereas bioerosion by Entobia isp. characterizes the equivalent facies in the Falmouth Fm. Crest facies in both localities show encrustation by secondary frame-builders as the dominant taphonomic process. The encrusting community of the Falmouth Fm. is dominated by calcareous algae such as Neogoniolithon sp. and Porolithon sp. The Port Morant Fm. encrusting community, however, is dominated by bryozoans, foraminifera, infilled serpulid worm tubes, and discontinuous Mesophyllum sp.

The difference in taphonomy of the back reef facies is likely a function of terrigenous input and relative time in the taphonomically active zone. The dissolution and microbialite development within the primary growth fabric of the Port Morant is evidence of increased freshwater and nutrient output during the Late Pleistocene in southeastern Jamaica. The encruster sequence in distal crest facies of the Port Morant Fm. also shows a similar signal of relatively high nutrient output compared to the Falmouth Fm. in north-central Jamaica.