Bulk carbonate isotope stratigraphy from CRP-3 core (Victoria Land Basin, Antarctica): evidence for Eocene-Oligocene palaeoclimatic evolution

Bulk carbonate isotope compositions and carbonate petrography from upper Eocene and lower Oligocene siliciclastic sediments of the CRP-3 sediment core (Victoria Land Basin, Antarctica) have been investigated with the aim of contributing to reconstruction of the Antarctic Cenozoic palaeoclimate. Most of the carbonate is calcite cement occurring as patches, nodules and horizons and consisting of equant and/or drusy sparry calcite, pervasive blocky calcite and rare poikilotopic calcite spar. 18O-depleted values (from −17 to −8 δ‰) of the CRP-3 carbonates suggest that the precipitating fluids were a mixing between marine and meteoric waters from melting glaciers. The δ18O record exhibits a number of steps in an upward increasing trend that are thought to reflect the evolution of ice-sheet growth over the late Eocene to early Oligocene in response to a global cooling trend. Low carbonate δ13C values in the CRP-3 drillcore suggest that organic reactions have played a significant role in modifying the pore fluid chemistry. Some anomalously light carbon compositions (down to −25‰) are interpreted to record methane-derived CO2 addition to the system.