Deep Sea Drilling Project Leg 72: Southwest Atlantic paleocirculation and Rio Grande rise tectonics

Petrology and Geochemistry of Basaltic Rocks from Rio Grande Rise, South Atlantic: Deep Sea Drilling Project Leg 72, Hole 516F

“…In contrast to the previous studies of rocks from the Rio Grande Rise, preliminary work on the igneous rocks recovered at DSDP Site 516F, Leg 72 (Barker et al, 1981) suggested that these samples had tholeiitic affinities but with higher concentrations of incompatible elements such as Ti, P, Zr, Nb, Y, La, and Ce in comparison to typical mid-ocean ridge basalts (MORB). A Santonian-Campanian age (84.5 Ma) for basement is inferred from the age of overlying sediments and identifi- cation of Magnetic Anomalies 33 and 34 to the east of the site (site chapter, Site 516, this volume).…”

“…These basalts were erupted at approximately the same period. Barker et al (1981) noted that the Hole 516F basalts were enriched in incompatible elements compared to typical MORB (i.e. the normal or N-type of Sun et al, 1979, or Group I of Bryan et al, 1976.…”

Late Miocene to Earliest Pliocene (9.8–4.5 Ma) Paleoceanography of the Subantarctic Southeast Atlantic: Stable Isotopic, Sedimentologic, and Microfossil Evidence

“…Based upon high-resolution carbon isotopic data from DSDP Hole 552A, Keigwin et al (1987) suggested that the general North Atlantic deep circulation was unaffected by the Messinian salinity crisis. Intervals of intense carbonate dissolution or hiatuses in the tropical and subtropical Atlantic (Ryan et al, 1974;Thunell, 1981;Shipboard Scientific Party, 1977;Barker et al, 1981) have been attributed to decreased NADW production leading to an older, CO 2 -enriched bottom water (Johnson, 1982). In Hole 642B in the Norwegian Sea, the late Miocene is marked by periods of carbonate dissolution lasting several hundreds of thousands of years, suggesting intervals of reduced ventilation and diminished production of NADW (Jansen et al, in press).…”

Carbonate Spikes and Displaced Components at Deep Sea Drilling Project Site 515: Pliocene/Pleistocene Depositional Processes in the Southern Brazil Basin

“…In addition, we observed Tertiary discoasters displaced into late Quaternary sediments. Although the "Karbonat Bombe" (Müller and Gastner, 1971) system on board provided only a crude estimate of absolute carbonate (reproducibility of only ±4%; Dunn, 1980), and our sample spacing was too coarse (about 50 cm intervals) to provide sufficient resolution, we speculated that carbonate preservation might be a cyclic response of the deep Brazil Basin to chemical changes in bottom water, in turn resulting from climatically controlled fluctuations in production of deep water around Antarctica (Barker et al, 1981). We were unable to correlate individual carbonate events with climatic cycles directly because of the paucity of fossils in the interbedded hemipelagic muds.…”