Abstract
Recent work has demonstrated the use of Sr/Ca and Mg/Ca ratios in the calcite of ostracod shells for reconstructing the palaeosalinity and palaeotemperature of lakes. In this study, the technique was applied to a lacustrine sequence of late Quaternary age (the upper Karewa Formation) in Kashmir, northwest Himalaya. Ostracods are the only fossils found in abundance in the upper Karewa sediments and are thus important for the reconstruction of upper Karewa palaeoenvironments. Trace-element analyses of multiple-shell samples of the ostracod Ilyocypris bradyi Sars 1890 were performed using inductively coupled plasma-atomic emission spectrometry. The results show that the palaeo-lake was even more dilute than the modern residual lakes in Kashmir. Reconstructed molar Sr/Ca ratios for the palaeo-lake waters vary between 30·10 −4 and 42·10 −4 compared with observed values of (46–110)·10 −4 for the modern residual lakes. Changes in the molar Mg/Ca ratios with unchanging Sr/Ca are attributed to variations in water temperature. The palaeo-lake probably receded from the study site at between 116 and 80 ka and lacustrine sedimentation gave way to subaerial loess deposition. The lack of any increasing trend in the reconstructed Sr/Ca values, together with structural and sedimentological evidence, suggests that the lake was drained by tectonic tilting or warping of the basin floor rather than by climatically-induced desiccation.
Published Version
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