Upper Cretaceous Nannofossils from Leg 120, Kerguelen Plateau, Southern Ocean

Drilling on the Kerguelen Plateau during Leg 120 cored the most complete, best preserved record of the Late Cretaceous of the Southern Ocean to date. Two calcareous pelagic sedimentary sections (Sites 747 and 750) provide a record from the upper Turonian(?)-lower Coniacian through the Maestrichtian. Two major disconformities interrupt the record: upper Coniacian-lower Santonian and mid-Campanian. Site 748 contains a CampanianMaestrichtian record of neritic sedimentation dominated by nannofossil-bearing, intermittently silicified, glauconitic bioclastic grainstones to wackestones. Parts of the upper Maestrichtian and the mid-Campanian are absent at this site. A set of 21 biostratigraphic events were used to correlate these sections. This combination of cosmopolitan and austral events allowed local, regional, and global correlation. Correlation of this scheme from the pelagic sites to the neritic site indicates the applicability of this system to the sparse, restricted assemblages of the upper Campanian and lower Maestrichtian. Comparison of the Kerguelen assemblages with previous records indicates weak provincialism and little endemism in the Coniacian through early Campanian Southern Ocean. Strong provincial distinction with high endemism is typical of the late Campanian through Maestrichtian. The change from weak to strong provincialism coincides with the mid-Campanian disconformity. The event marked or masked by this disconformity must have involved ecological decoupling of the Southern Ocean from more temperate surface-water masses. A new species, Zeugrhabdotus kerguelenensis, is named.