Insights into geophysical downhole logging data from the ICDP project ‘The Nam Co Drilling Project, Tibet (NamCore)’

The Tibetan Plateau is part of a region often referred to as the ‘Third Pole’ because its ice fields are the world’s largest outside the polar regions.  Almost one third of the world's population depends on the water supply from the Tibetan Plateau and future climate change will have a large impact on the region, affecting the water cycle, water resources, ecology and the economy. To assess predictive climate model scenarios, it is crucial to improve our understanding of the timing, duration and intensity of past climatic variability and its environmental impact in this sensitive area over long geologic time scales. For this, we use a sequence of lacustrine sediments from the Tibetan Plateau, which was acquired during the drilling campaign for the international ICDP project ‘The Nam Co Drilling Project, Tibet (NamCore)’ that was carried out in June/July 2024. The lake is located 4700 m above sea level, has a maximum depth of approximately 100 m, and covers an area of more than 2000 m². In contrast to much younger and often incomplete climate archives on the Tibetan Plateau, the sedimentary sequence of Nam Co contains continuous information on climate history with age estimations of more than one million years. The investigation of this sequence will cover several cycles of glacial and interglacial stages.

The LIAG Institute for Applied Geophysics completed geophysical downhole measurements at the drill site in the central area of the lake. This involved multi-tool logging of two boreholes down to a depth of 185 m and 360 m below lake floor, respectively. Preliminary analyses reveal several lithological units that can be characterised by their physical properties. In addition, certain sections exhibit cyclic variations in the sedimentary sequence. This is beneficial for cyclostratigraphy and time series analyses, which in turn can lead to the creation of a robust time-depth scale.

Information on depositional age and lithology will be combined to derive statements on the relationship between aridity and precipitation in the past and to interpret these in the context of global climate development.