Shipboard studies suggest Pliocene sedimentation in the Cape Basin is approximately continuous at Site 1085 (Wefer, Berger, Richter, et al., 1998), so an orbitally tuned age model was developed to constrain the timing of the geochemical and lithologic changes in the Cape Basin using core and well log data. Geochemical and lithologic variations (Ellershaw et al., in press, this volume; Christensen et al., 1999; Kalbas et al., 1999; Wefer, Berger, and Richter, et al., 1998) suggest that the onset of Northern Hemisphere glaciation had a significant impact on the oceanography of the Cape Basin (Fig. F1). A high-resolution age model is necessary to identify the response of the Cape Basin to Northern Hemisphere glaciation and to compare the record of onset in both hemispheres.

This paper outlines the creation of an age model sufficient for high-resolution climate change studies on core material. It was generated by orbitally tuning the composite section and tested using standard techniques of spectral analysis. The spectral and cross-spectral analyses suggest a systemic relationship between deposition in the Cape Basin and orbital forcing; however, proxies are necessary to determine whether the relationship is coincident or causative. Thus, the final stage of the project, a comparison of the Cape Basin records with other records of climate change, particularly those in the Northern Hemisphere, will be the subject of a future paper.