Geology and sediment accumulation rates at Carrie Bow Cay, Belize

Abstract

A 24 km long transect of cores consisting of four rotary drill cores and seven vibrocores was drilled in a line extending from the seaward side of the reef crest at Carrie Bow Cay to the mainland at a point between Sittee Point and the town of Stann Creek. Two of the four rotary cores were drilled seaward of the reef crest, one through a spur to a depth of 7.6 m and the other into the adjacent groove to a depth of 18.3 m. The two cores show no evidence that the spur and groove system was erosional in origin; rather they demonstrate that it was constructional. Submarine cementation, chiefly in the form of fine-grained high-magnesium calcite, was found mainly in cemented internal sediment in both cores drilled seaward of the reef crest. Two other rotary cores were drilled landward of the reef crest. One was drilled on the reef flat to a depth of 8.8 m, and the other was drilled on the southwest tip of Carrie Bow Cay to a depth of 17.7 m. Both cores encountered essentially uncemented carbonate reef sands with some coral rubble. Of the four rotary cores, only the Carrie Bow Cay core encountered Pleistocene bedrock. Radiocarbon dating of a large head of Siderastrea siderea , growing on bedrock from the Carrie Bow Cay core at a depth of 15.04 m below sea level, gave an age of 6960±110 years. The leached calcitic coralline bedrock, at a depth of 15.7 m below sea level in the Carrie Bow Cay core, contained root marks, and iron staining indicative of subaerial exposure.