(Table 1) Oxygen and carbon isotopic values of benthic foraminifera from the Upper Maastrichtian interval of various DSDP and ODP sites

Stable isotopic data from benthic foraminifera indicate the occurrence of at least three deepwater masses in the late Maastrichtian ocean. Given mean oceanic d18Ow of -1.0 per mil, the temperature of the coolest intermediate-depth waters was 5°-7°C, that of the deepest waters was 10°C, and that of the warmest intermediate waters was 13°-15°C. The cool intermediate-depth water mass probably originated in the high-latitude Southern Ocean. The deepest waters originated at least partly in the northern Atlantic. The source region for the warmest intermediate-depth water mass is unknown. Although much of the late Maastrichtian deep water was probably preconditioned for winter sinking by low- or middle-latitude evaporation, no more than ~11% of late Maastrichtian deep water could have been directly actuated by low-latitude sea surface evaporation. At least in the southern Atlantic and Indian Oceans, heat transport by upwelling of deep water was not the primary cause of mild sea surface and coastal temperatures.

Organic matter and trace element concentrations in sapropels from ODP Leg 160 sites

A distinct Pliocene eastern Mediterranean sapropel (i-282), recovered from three Ocean Drilling Program (ODP) Leg 160 Sites, has been investigated for its organic and inorganic composition. This sapropel is characterized by high organic carbon (Corg) and trace element contents, and the presence of isorenieratene derivatives. The latter suggests that the base of the photic zone was sulphidic during formation of the sapropel. Combined with evidence of bottom water anoxia (preservation of laminae, high redox-sensitive trace element contents, and the abundance and isotopic composition of pyrite) this leads to the tentative conclusion that almost the entire water column may have been anoxic. This anoxia resulted from high productivity and not from stagnation, because an approximation of the trace element budget during sapropel formation shows that water exchange with the western Mediterranean is needed. Entire water column anoxia has been suggested earlier for several black shales. With regard to the depositional environment and the Corg content, however, only the Cenomanian=Turonian Boundary Event (CTBE) black shales appear to be comparable to this sapropel. The proposed trace element removal mechanism of scavenging and (co-)precipitation in an anoxic water column, is thought to be similar for both types of deposits. The ultimate trace element source for the sapropel, however, is seawater, whereas it is hydrothermal and fluvial input for CTBE black shales (because they have a larger temporal and spatial distribution). Nonetheless, the Corg-rich eastern Mediterranean Pliocene sapropel discussed here may be considered to be a younger analogue of CTBE black shales.