Benthic foraminifera in Southwest Indian Ocean surface sediments

• Main Author: Corliss, Bruce H
• Format: Other/Unknown Material
• Language: English
• Published: PANGAEA 1983
• Subjects: AII15-765; AII15-766; AR4-55; Argo; DODO; DODO-131; DODO-148; DODO-149; DODO-151G; GC; Gravity corer; Horizon; Indian Ocean; LSDA; LSDA-122G; LSDA-123G; LSDH; LSDH-025G; LUSIAD-A; LUSIAD-H; MONS01AR-MONS08AR; MONSOON; MSN-55G; MSN-56P; MSN-61G; MSN-62G; PC; Piston corer; RC11; RC11-101; RC11-103; RC1112; RC14; RC14-12A; RC17; RC17-63; RC17-80; RC17-81; RC17-82; RC17-83; RC17-84; RC17-85; RC17-88TW; RC17-90; RC17-92; RC17-93; RC17-94; RC17-95; RC17-97; Robert Conrad; Antarc*; Antarctic; North Atlantic Deep Water; North Atlantic
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.777974; https://doi.org/10.1594/PANGAEA.777974

The distribution of deep-sea benthonic foraminifera in core top samples from the southwest Indian Ocean is examined. Principal component analysis reveals two major assemblages. One assemblages between 3600 and 4800-m water depth is dominated by Episominella umbonifera and is associated with cold (Theta = -0.3 to 0.8°C), low salinity (34.66 to 34.72 * 10**-3) Antarctic Bottom Water in the Crozet Basin, in fracture zones, and on the flanks of the Southwest Indian Ridge. A second assemblage, dominated by Planulina wuellerstorfi, Globocassidulina subglobasa, Astrononion echolsi and Pullenia bulloides, is between 1600 and 3800 m on the Crozet Plateau, Madagascar Ridge, Central Indian Ridge, and Southwest Indian Ridge and is associated with relatively warm (Theta = 0.8 to 2.6°C), high salinity (34.72 to 34.76 * 10**-3) North Atlantic Deep Water. The third principal component divides the P. wuellerstorfi assemblage into two subgroups. One is dominated by Epistominella exigua, P. bulloides, P. wuellerstorfi, and A. echolsi and a second is dominated by G. subglobosa. The distribution of the E. umbonifera assemblage and previous hydrographic studies suggest that AABW flows as a western boundary contour current in the Crozet Basin and penetrates fracture zones in the Southwest Indian Ridge between 55 and 57°E and near 66°E as it travels northward into the Madagascar and Mascarene basins. The faunal-water mass associations from the southeast Indian Ocean are compared; the most notable faunal difference is the absence of Uvigerina as a dominant taxon in the southwest Indian Ocean. A comparison of dissolved oxygen and Uvigerina data shows that oxygen is not a major influence upon the distribution of Uvigerina. A correlation analysis of the faunal data and water depth, potential temperature, in situ temperature, salinity, dissolved oxygen, and 1 - Omega, an index of calcium carbonate undersaturation, was carried out to determine the relationships between fauna and hydrography. The second principal component has a significant ...