ABSTRACT

Relative and absolute abundance variations of planktonic foraminifera from eight piston cores provide the framework for examining the latest Pleistocene meltwater influx into the north-central Gulf of Mexico, the associated sedimentation patterns, and the effects of these sedimentation patterns on the stratigraphic expression of the faunal signal. Sediment accumulation rates throughout the lower bathyal and abyssal regions of the northwestern Gulf are noticeably variable indicating that sedimentary processes in this region are complex and may involve several different sediment sources and/or transport mechanisms.

Two salinity-sensitive species, Globigernoides ruber, a commonly used faunal indicator of the meltwater spike, and Neogloboquadrina dutertrei exhibit relative frequency increases in the Y1 subzone. The relative frequency increases of G. ruber and N. dutertrei are consistent throughout the north-central Gulf, showing no clear trend of increasing or decreasing basinward as has been previously suggested. The consistent occurrence in all the cores of a G. ruber absolute frequency peak in the early Holocene, which trails the relative frequency peak in Y1, reflects the G. ruber population increase resulting from the decline in other planktonic species during the Y1 meltwater event. In contrast, both the absolute and relative frequency peaks of N. dutertrei occur in the early Holocene rather than in the meltwater interval (Y1). With the onset of more equitable conditions and the population increase in other species, G. ruber populations declined. These trends support the idea that G. ruber dominated by default during the Y1 meltwater event because other species were unable to proliferate under the harsh meltwater temperature and salinity conditions.