Pliocene-Pleistocene distribution of benthic foraminifers from ODP Hole 110-672A (Table 2)

Site 672 is located on the Atlantic abyssal plain to the east of the Lesser Antilles forearc region. It serves as a stratigraphic reference section for sediments entering the Barbados accretionary prism. A relatively complete Pliocene through lower Pleistocene section was recovered from Site 672 that contains a moderately well-preserved population of benthic foraminifers. Q-mode factor analysis of the benthic population data identified three Pliocene-Pleistocene assemblages that inhabited this site. The Factor 1 fauna, characterized by Nuttallides umboniferus, is commonly associated with the presence of Antarctic Bottom Water (AABW). The Factor 2 assemblage is characterized by Globocassidulina subglobosa, Epistominella exigua, and a combined category of unilocular species. The Factor 3 assemblage is characterized by Epistominella exigua, and Planulina wuellerstorfi. The Factor 2 and 3 faunas are associated with bottom water significantly warmer than that preferred by the Factor 1 assemblage. The distribution of these assemblages has been used to distinguish three climatic intervals in the abyssal environment during the Pliocene-Pleistocene. An early Pliocene warm interval occurred from the Ceratolithus rugosus Subzone to the middle of the Discoaster tamalis Subzone. The upper Pliocene is characterized by oscillations between the Factor 1 and Factor 2 assemblages, which suggests climatic deterioration and increased pulses of AABW flow. The persistence of an essentially modern (Factor 1) fauna throughout the early Pleistocene suggests full glacial development at both poles and a substantial volume of AABW production.

(Table S1, S4) Campanian-Maastrichtian benthic foraminifera from ODP Hole 113-690C

During the latest Cretaceous cooling phase, a positive shift in benthic foraminiferal d18O values lasting about 1.5 Myr (71.5-70 Ma) can be observed at a global scale (Campanian-Maastrichtian Boundary Event, CMBE). This d18O excursion is interpreted as being influenced by a change in intermediate- to deep-water circulation or by temporal build-up of Antarctic ice sheets. Here we test whether benthic foraminiferal assemblages from a southern high-latitudinal site near Antarctica (ODP Site 690) are influenced by the CMBE. If the d18O transition reflects a change in intermediate- to deep-water circulation from low-latitude to high-latitude water masses, then this change would result in cooler temperatures, higher oxygen concentration, and possibly lower organic-matter flux at the seafloor, resulting in a major benthic foraminiferal assemblage change. If, however, the d18O transition was mainly triggered by ice formation, no considerable compositional difference in benthic foraminiferal assemblages would be expected. Our data show a separation of the studied succession into two parts with distinctly different benthic foraminiferal assemblages. Species dominating the older part (73.0-70.5 Ma) tolerate less bottom water oxygenation and are typical components of low-latitude assemblages. In contrast, the younger part (70.0-68.0 Ma) is characterized by species that indicate well-oxygenated bottom waters and species common in high-latitude assemblages. We interpret the observed change in benthic foraminiferal assemblages toward a well-oxygenated environment to reflect the onset of a shift from low-latitude toward high-latitude dominated intermediate- to deep-water sources. This implies that a change in oceanic circulation was at least a major component of the CMBE.

Late Oligocene to Recent benthic foraminifers from the northeastern North Atlantic

Deep-sea benthic foraminiferal faunas were studied from Sites 608 (depth 3534 m, 42°50'N, 23°05'W) and 610 (depth 2427 m, 53°13'N, 18°53'W). The sampling interval corresponded to 0.1 to 0.5 m.y. at Site 608 and in the sections of Site 610 from which core recovery was continuous. First and last appearances of benthic foraminiferal taxa are generally not coeval at the two sites, although the faunal patterns are similar and many species occur at both sites. Major periods of changes in the benthic faunas, as indicated by the numbers of first and last appearances and changes in relative abundances, occurred in the early Miocene (19.2-17 Ma), the middle Miocene (15.5-13.5 Ma), the late Miocene (7-5.5 Ma), and the Pliocene-Pleistocene (3.5-0.7 Ma). A period of minor changes in the middle to late Miocene (10-9 Ma) was recognized at Site 608 only. These periods of faunal changes can be correlated with periods of paleoceanographic changes: there was a period of sluggish circulation in the northeastern North Atlantic from 19.2 to 17 Ma, and the deep waters of the oceans probably cooled between 15.5 and 13.5 Ma, as indicated by an increase in delta18O values in benthic foraminiferal tests. The period between 10 and 9 Ma was probably characterized by relatively vigorous bottom-water circulation in the northeastern Atlantic, as indicated by the presence of a widespread reflector. The faunal change at 7 to 5.5 Ma corresponds in time with a worldwide change in delta13C values, and with the Messinian closing of the Mediterranean. The last and largest faunal changes correspond in time with the onset and intensification of Northern Hemisphere glaciation.

(Appendix B) Benthic foraminifera in Indian Ocean surface sediments

Multivariate analysis was performed on percentages of 46 species of unstained deep-sea benthic foraminifera from 131 core-top to near-core-top samples (322-5013 m) from across the Indian Ocean. Faunal data are combined with GEOSECS geochemical data to investigate any relationship between benthic foraminifera (assemblages and species) and deep-sea properties. In general, benthic foraminifera show a good correlation to surface productivity, organic carbon flux to the sea floor, deep-sea oxygenation and, to a lesser extent, to bottom temperature, without correlation with the water depths. The foraminiferal census data combined with geochemical data has enabled the division of the Indian Ocean into two faunal provinces. Province A occupies the northwestern Indian Ocean (Arabian Sea region) where surface primary production has a major maximum during the summer monsoon season and a secondary maximum during winter monsoon season that leads to high organic flux to the seafloor, making the deep-sea one of the most oxygen-deficient regions in the world ocean, with a pronounced oxygen minimum zone (OMZ). This province is dominated by benthic foraminifera characteristic of low oxygen and high organic food flux including Uvigerina peregrina, Robulus nicobarensis, Bolivinita pseudopunctata, Bolivinita sp., Bulimina aculeata, Bulimina alazanensis, Ehrenbergina carinata and Cassidulina carinata. Province B covers southern, southeastern and eastern parts of the Indian Ocean and is dominated by Nuttallides umbonifera, Epistominella exigua, Globocassidulina subglobosa, Uvigerina proboscidea, Cibicides wuellerstorfi, Cassidulina laevigata, Pullenia bulloides, Pullenia osloensis, Pyrgo murrhina, Oridorsalis umbonatus, Gyroidinoides (= Gyroidina) soldanii and Gyroidinoides cf. gemma suggesting well-oxygenated, cold deep water with low (oligotrophic) and pulsed food supply.

Benthic foraminifera in eastern equatorial Indian Ocean surface sediments

Study of Recent abyssal benthic foraminifera from core-top samples in the eastern equatorial Indian Ocean has identified distinctive faunas whose distribution patterns reflect the major hydrographic features of the region. Above 3800 m, Indian Deep Water (IDW) is characterized by a diverse and evenly-distributed biofacies to which Globocassidulina subglobosa, Pyrgo spp., Uvigerina peregrina, and Eggerella bradyi are the major contributors. Nuttalides umbonifera and Epistominella exigua are associated with Indian Bottom Water (IBW) below 3800 m. Within the IBW fauna, N. umbonifera and E. exigua are characteristic of two biofacies with independent distribution patterns. Nuttalides umbonifera systematically increases in abundance with increasing water depth. The E. exigua biofacies reaches its greatest abundance in sediments on the eastern flank of the Ninetyeast Ridge and in the Wharton-Cocos Basin. The hydrographic transition between IDW and IBW coincides with the level of transition from waters supersaturated to waters undersaturated with respect to calcite and with the depth of the lysocline. Carbonate saturation levels, possibly combined with the effects of selective dissolution on the benthic foraminiferal populations, best explain the change in faunas across the IDW/IBW boundary and the bathymetric distribution pattern of N. umbonifera. The distribution of the E. exigua fauna cannot be explained with this model. Epistominella exigua is associated with the colder, more oxygenated IBW of the Wharton-Cocos Basin. The distribution of this biofacies on the eastern flank of the Ninetyeast Ridge agrees well with the calculated bathymetric position of the northward flowing deep boundary current which aerates the eastern basins of the Indian Ocean.