Ostracods from sediment cores of the ICDP NamCore drilling project provide insights into long-term lacustrine evolution on the Tibetan Plateau

Ostracods from sediment cores of the ICDP NamCore drilling project were analysed to document their distribution, abundance, and preservation, and to explore their potential for reconstructing past lacustrine conditions on the central Tibetan Plateau. Selected core catcher samples covering sediment depths from ~8 to 470 m were investigated for their microfossil content. Sediment samples (10–15 g each) were wet-sieved at 63 µm and 200 µm, and the >200 µm fraction was examined under a stereomicroscope. Ostracods were assessed semi-quantitatively and assigned to five abundance categories (absent, 1-10, >10, >100, >1000 valves per sample). Preservation states were evaluated qualitatively, and taxonomic identifications were based on established regional faunal keys.

Ostracods represent the only fossils observed in the sand-sized fraction of the analysed samples. Their abundance varies strongly, ranging from complete absence to more than 1000 valves per sample, with approximately half of the samples containing more than 100 valves. Preservation is generally good, although weakly etched, fragmented, compacted, or deformed valves occur, particularly below ~180 m core depth. Assemblages are of low diversity, with a maximum of five species per sample. At least six ostracod taxa were identified, including Leucocytherella sinensis, ?Leucocythere dorsotuberosa, ?Leucocythere postilirata, Ilyocypris ?bradyi, a smooth Ilyocypris species of uncertain taxonomic status, and juvenile Candona spp. The taxonomic assignment of ?Leucocythere dorsotuberosa and the smooth Ilyocypris species is the subject of ongoing investigations.

Variations in ostracod abundance, species level assemblage composition, and variable preservation suggest changes in depositional and post-depositional conditions through the core. While the presence of ostracods throughout most sections is consistent with predominantly lacustrine settings, intervals with low abundances or poor preservation may reflect a range of factors, including lake-level changes, sedimentation dynamics, or taphonomic overprinting. Further quantitative analyses, improved taxonomic resolution, and integration with independent proxies are required to refine palaeoenvironmental interpretations.