Paleocene to Middle Eocene calcareous nannofossils of ODP Sites 689 and 690, Maud Rise, Weddell Sea

Abstract

Cores from Sites 689 and 690 of Ocean Drilling Program Leg 113 provide the most continuous Paleocene and Eocene sequence yet recovered by deep sea drilling in the high latitudes of the Southern Ocean. The presence of warm water index fossils such as the discoasters and species of the Tribrachiatus plexus facilitate the application of commonly used low latitude calcareous nannofossil biostratigraphic zonation schemes for the upper Paleocene and lower Eocene intervals. In the more complete section at Site 690, Okada and Bukry Zones CP1 through CP10 can be identified for the most part with the possible exception of Zone CP3. Several hiatuses are present in the sequence at Site 689 with the most notable being at the Cretaceous/Tertiary and Paleocene/Eocene boundaries. Though not extremely diverse, the assemblage of discoasters in the upper Paleocene and lower Eocene calcareous oozes is indicative of warm, relatively equable climates during that interval. Climatic cooling is indicated for middle Eocene sediments by assemblages that contain very abundant Reticulofenestra, lack common discoasters and sphenoliths and are much less diverse overall. -from Authors