Distribution of Foraminiferal Tests in Sediments of Serranilla Bank, Nicaraguan Rise, Southwestern Caribbean

Serranilla Bank (16°N 80°W) is one of several small, carbonate platforms located on the Nicaraguan Rise, a tectonically derived structural feature in the southwest Caribbean. These platforms are dominated by chloralgal and molluscan sediments despite their tropical setting and isolation from terrigenous sedimentation. Banks of the central and western Nicaraguan Rise have relatively deep banktops (10-40m) and appear to be failing to keep up with Holocene sea-level rise. Thus, they may be useful analogues for the study of drowned platforms in the geologic record. Foraminifera from Serranilla Bank were examined in 31 sediment samples. Analysis revealed Discorbis rosea-dominated foraminiferal assemblages, which are normally associated with platform-margin environments in other areas of the Caribbean, occurring on the banktop. The preponderance of this robust species is probably the result of the relatively deep banktop depths and dynamic hydrographic conditions found on this platform