The Kalkkop Impact Crater, South Africa, an environmental archive for MIS 7 and beyond

The Kalkkop meteorite impact crater, situated within the semi-arid Nama-Karroo biome, has long been the subject of investigation. Palaeolake deposits were confirmed after three cores were drilled in the 1990s describing the fine-grained, laminated limestone stratigraphy interspersed with an abundance of fossil material. Investigations based on these cores, suggested that during the period of deposition the region experienced alternating wetter and drier climates. However, the environmental reconstruction was based on a limited number of samples over the length of the core (~90 m) and very sparse chronology. Additionally, the core was severely disintegrated due to poor handling and storage post-retrieval. New cores were drilled at Kalkkop crater in early 2019 and are curated in a custom-built cold storage facility at the University of Cape Town. Here we present data from the longer of the two cores, an 89 m long core from the centre of the crater with close to 80% core recovery. Surface palaeolake samples have been dated to the beginning of MIS 7 (~250 ka) using U–Th series, suggesting the lake deposits may cover, at least in part, the glacial termination III, a period rarely documented for southern Africa. Here, we provide preliminary results from the top 20 m based on sediment colour characteristics, XRF, ICP, biogenic silica and CNS analyses. Future research will focus on a more detailed U-Th chronology, annual layer counting and the generation of a detailed age model. The implications of this new palaeoclimate archive presented here, plus its future age model, are significant given the sites close proximity to the rich archaeological record of early modern human behaviour on the adjacent southern Cape coast.