The ICDP Nam Co Drilling Project (NamCore), Tibet: a 510.2 m sedimentary record from the Third Pole

The Nam Co Drilling Project (NamCore) is a multinational and interdisciplinary research initiative designed to understand long-term climatic variability and associated environmental change on the Tibetan Plateau. The project primarily targets the timing and magnitude of Indian/East Asian monsoon variability and its interplay with the Westerlies. Thereby, the glacial–interglacial history and dynamics at high altitude; the impact of geological and environmental changes on (micro-)biological processes; the evolution and resilience of high-altitude ecosystems, including the deep biosphere; and geomagnetic variations during the Quaternary are of special interest. For in-depth investigations regarding the outlined research purposes, the (mostly) calcareous sediments of Nam Co, one of the largest and deepest lakes on the Tibetan Plateau, were targeted within the framework of the International Continental Scientific Drilling Program (ICDP) and cored in May–July 2024 (ICDP Expedition 5073). Altogether, 1415.45 m was drilled and 1175.99 m cored, with 950.77 m of sediment recovered (core recovery of 80.8 %) from seven holes at one site (5073_1) situated at a water depth of ∼ 93 m, reaching a maximum depth of 510.2 m below the lake floor. Initial results from core descriptions and preliminary core catcher analyses suggest that the sediments of Nam Co reflect the evolution of a dynamic high-altitude lake system over multiple glacial–interglacial cycles. Four major lithologies are observed in the drill cores (calcareous mud, non-calcareous mud, calcareous mud with ferric staining and sand) and grouped into five major lithological units based on their physicochemical characteristics obtained from core catcher material. Micropaleontological results from core catcher material reveal a general absence of diatoms, due to unsuitable growing and/or preservation conditions, while ostracods abundances, preservation, and species composition vary, which might be linked to environmental changes and/or changing preservation conditions. Shifts in n-alkane chain length might be attributable to lake-level variations and/or glacial–interglacial cycles.