Late Quaternary changes in moisture availability and weathering intensity on the central Tibetan Plateau indicated by chemical signatures of ostracod shells

High-resolution multi-proxy records from two lakes on the southern Tibetan Plateau, Nam Co and Tangra Yumco, are used to infer long-term variations in the Asian monsoon system with a novel set of ostracod shell chemistry proxies. We track the moisture evolution since the Last Glacial Maximum using the trace element, rare earth element (REE) and stable isotope composition of ostracod shells. The sediment records covering the past 18.8 cal. ka BP and 17.4 cal. ka BP, respectively, demonstrate the suitability of REEs as indicators of weathering intensity and thus hydrological changes and moisture sources in the catchment. In Nam Co, high concentrations of light REEs between 14 and 13 cal. ka BP suggest an increased drainage from the glaciated Nyainqêngtanglha Mountains in the south, pointing to meltwater input. REEs in ostracod shells therefore provide additional information on water sources critical for the interpretation of stable isotope records. Mg/Ca, Sr/Ca, and Ba/Ca ratios reflect salinity and thus changes in effective moisture. Asynchronous behavior of Mg/Ca, Sr/Ca, and Ba/Ca ratios are controlled by changes in dominance of precipitating carbonate minerals in the lake. Synchronous behavior reflects calcite precipitation, indicating low-Mg/Ca warm-wet conditions. Constantly low Sr/Ca ratios reflect aragonite precipitation, indicating high-Mg dry conditions. Increased Sr/Ca and Ba/Ca relative to Mg/Ca ratios show monohydrocalcite precipitation, indicating high-Mg/Ca cold-dry conditions. Furthermore, Fe/Ca, Mn/Ca and U/Ca ratios in ostracods reflect changes in oxygen saturation in lake bottom waters controlled by lake level and microbial activity. The paleoclimate histories reconstructed from Nam Co and Tangra Yumco show high similarity throughout the late Quaternary. We identified two major dry periods, corresponding to Heinrich 1 and the Younger Dryas, followed by strengthening in Indian summer monsoon precipitation. The early Holocene is characterized by a moisture maximum, reflecting abundant water supply by a strong ISM. A time-delayed shift to dry conditions occurred at 2.6 cal. ka BP at Tangra Yumco, and at 2 cal. ka BP at Nam Co, resulting in decreasing lake levels, caused by weakened monsoon intensity due to a southeastward migration of the ISM-Westerly boundary with an estimated velocity of approximately 600 m per year

Trace elements, stable isotopes and rare earth elements in ostracod valves from sediment cores from Lake Nam Co and Tangra Yumco, Tibetan Plateau

High-resolution multi-proxy records from two lakes on the southern Tibetan Plateau, Nam Co and Tangra Yumco, are used to infer long-term variations in the Asian monsoon system. We examine the moisture evolution during the Late Glacial Maximum and Holocene using the trace element and stable isotope composition of ostracod shells. The sediment records covering the past 24 cal. ka BP and 18 cal. ka BP, respectively, demonstrate the suitability of ostracod shell chemistry as paleoenvironmental proxy. We analysed (i) Mg/Ca, Ba/Ca and Sr/Ca ratios as salinity proxies, (ii) Fe/Ca, Mn/Ca and U/Ca ratios representing redox conditions and microbial activity, and (iii) rare earth elements (REEs) reflecting weathering and changes in provenance

Millennial hydrological variability in the continental northern Neotropics during Marine Isotope Stages (MISs) 3-2 (59-15 cal ka BP) inferred from sediments of Lake Peten Itza, Guatemala

Peer reviewe

Geochemical and mineralogical record of MIS3-2 from Lake Petén Itzá (PI-02 Site) Guatemala

Inorganic geochemistry data (Ti, Al, Ca, Fe, and Mn) and mineralogy of sediments from Lake Petén Itzá are presented. Lake Petén Itzá was drilled in 2006 by the International Continental Discovery Program, obtaining seven lacustrine sedimentary records: PI-01, PI-02, PI-03, PI-04, PI-06, PI-7, and PI-9. Here, we present data from site PI-02 located north of the lake (16°59'58.04''N; 89°44'41.51''W) and measured between 67 and 19 m depth. Inorganic geochemistry data were obtained by X-ray fluorescence (XRF) using a Cox Analytical Itrax Core Scanner (Cr tube, 30 kV, 55 mA, 15 s exposure) with a resolution of 1 cm. XRF data is displayed in counts per second (cps). Subsequently, a transformation to centered log-ratio (CLR) was performed. The CLR data were obtained by dividing each value by the geometric mean of the elements measured at said depth, then the natural logarithm of said quotient was obtained. CLR results have no units. The mineralogy data were obtained every 1 m by ray diffraction (XRD) using a Rigaku MiniFlex 600 equipment (15 mA/40kV) in a rotation axis between 3 and 80°. The XRD values are in relative percentages obtained using the X-Pert High Score software (version 1.0b) and the diffraction potential files of the International Center for Diffraction Data, USA. Depth data corresponds with the master composite sequence presented by Mueller et al. (2010), while age data belongs to the age-depth model presented by Martínez-Abarca et al. 2023