ABSTRACT

The Gyre Basin, situated 250km. off the Texas coast, is the site of a preliminary study of living benthic foraminiferal assemblages from oxic (oxygenated) intraslope basin environments. The Gyre Basin was formed by the blockage of a submarine canyon by rising salt diapirs and is similar to other intraslope basins in the northern Gulf of Mexico. The environmental conditions are markedly different at the Basin rim and Basin floor, and this is reflected in the composition of the modern foraminiferal assemblages. Rim sediments are composed primarily of pelagic tests and detrital clay particles which have accumulated at a slow and steady rate, whereas the deeper sediments are derived chiefly from the slumping of Basin walls, the result of diapiric uplift. Sediment accumulation is considerably faster on the bottom than on the rim of the Basin, and occurs intermittently. Thirty-seven species of living benthic foraminifera, including Ammobaculites gyrensis n.sp., and 82 non-living species are found in rim sediments, but samples from the deepest region of the Basin contain only one living specimen within the 26 species collected there. A total of 38 living and 85 dead species was identified. Sediment accumulation rate and mode appear to determine assemblage composition.