An over 500,000 years lacustrine core in the high-altitude lake Nam Co of the Tibet Plateau

Located in the heart of the Tibetan Plateau, Nam Co is a closed lake spanning over 2,000 square kilometers and situated at an elevation exceeding 4,700 meters. The sediment thickness within the lake exceeds 700 meters, providing comprehensive insights into the climate and environmental conditions covering several glacial and interglacial cycles. With the support of the International Continental Scientific Drilling Program (ICDP) and China's Second Tibet Integrated Expedition Project (STEP), the Namcore drilling project aims to achieve: (1) Reconstructing the long-term climate change history across multiple glacial-interglacial stages and elucidating its relationship with global atmospheric circulation patterns; (2) Investigating the evolution and resilience of high-altitude terrestrial and lacustrine ecosystems under glacial and interglacial climate conditions; (3) Understanding the metabolic factors influencing lake sediment microbial communities in various glacial-interglacial environments; (4) Providing fundamental observation data on paleomagnetic changes to simulate the paleomagnetic field prior to the Holocene epoch. Depending on a stable and wind-resistant drilling barge manufactured in China, and a skilled drilling team as well as the long-term used drilling equipment provided by ICDP, the field campaign was successfully conducted from June 6 to July 17 of 2024, resulting in the retrieval of a total length of 950 meters of lake core. The deepest depth reached by the drill exceeded 510 meters. Based on seismic survey data, it is anticipated that the age of the lake core surpasses MIS 13 stage (approximately 550,000 yrs BP). Furthermore, the average resolution achieved is as high as 10 yrs cm^-1. A combination of multiple dating methods will be employed in order to establish a robust deposition time series. ¹⁴C will be utilized for sediments less than 50,000 yrs BP while OSL and post-IR IRSL method will be employed to date back approximately 200,000 yrs BP. For more older deposits, amino acid racemization (AAR), uranium/thorium ratio (U/Th), cosmic ray Beryllium isotope (¹⁰Be/⁹Be), as well as geomagnetic polarity analysis, thermochronology assessment and cyclic stratigraphy will be integrated to obtain reliable chronological sequences of cores. Proxies will be utilized to indicate climate and environmental changes, such as geochemical indicators, pollen, biomarkers, sedaDNA, environmental magnetic indicators, etc. for reconstructing paleo-temperature, precipitation, water level, vegetation, aquatic biodiversity and other changes in the lake basin. The relationship between these changes and atmospheric circulation changes and glacial activities in the lake basins will be also discussed.