Paleotemperature Trends for the Campanian through Paleocene Reconstructed using Molecular Proxies from the Transkei Basin

Abstract

Gradual cooling characterizes the trend in Late Cretaceous climate for southern high latitudes, likely associated with decreasing atmospheric CO2, the progressive breakup of Gondwana and widening of the Southern Ocean basin. Recovery of Campanian through Paleocene organic-rich sediments (∼78 – 60 Ma) from the Transkei Basin (Site U1581), offshore South Africa, during IODP Expedition 392 enabled reconstruction of ocean paleotemperatures recording climatic evolution of the late Cretaceous Southern Ocean. Analysis of GDGTs originating from Nitrososphaerota and alkenones derived from haptophyte algae afforded temporal records for sea surface temperatures (SST) based on TEX86 and UK’40 molecular proxies. UK’40 represents an analog of the UK’37 proxy based on the ratio of C40 rather than C37 alkenones. The coherence between TEX86 and UK’40 supports the efficacy of the latter as a Cretaceous temperature proxy. Evidence for progressive cooling in the TEX86 record is consistent with other temperature reconstructions for the late Cretaceous. In addition, SSTs stratigraphic profiles for the Transkei Basin reveals several discrete cooling steps during the late Campanian and at the Campanian-Maastrichtian boundary not previously observed for this time interval.