Middle Miocene paleoenvironmental change and paleoelevation of the Lunpola Basin, Central Tibet

The Tibetan region underwent diachronous differential rises during the Cenozoic era. Its elevation history is critical for understanding the processes of mountain building, and for evaluating its climatic effects on atmo-spheric circulations. However, knowledge of paleoenvironment and paleoelevation in different geological do-mains of the Tibetan Plateau is still limited. Here we provide chronology of lacustrine deposits of the Upper Dingqing Formation in the Lunpola Basin in Central Tibet, which yields a middle Miocene age (15-12 Ma). Both stable isotope and palynological records indicate a climatic transition at similar to 13.8 Ma marked by a change towards a cooler and drier climate after the Middle Miocene Climate Transition driven by global climatic cooling. Pollen and spore assemblages suggest that the vegetation was dominated by mixed coniferous-broadleaved forest with some grasslands. New palynological elevation reconstructions constrained by the co-existence approach yield a maximum paleo-elevation of 3100-3600 m (average 3350 m) of the Lunpola Basin, which was consistent with a maximum elevation of 3400 m based on floating-leaf plants. Our new data do not support previous views that the Lunpola Basin achieved its current elevation as early as the late Eocene or early Oligocene, but instead we suggest there has been a rise of up to 1200 m since 12 million years ago. Our results bring new light on both the paleoenvironmental reconstructions and the paleo-elevation estimates of the Lunpola Basin, Central Tibet.

Automated summary

Through the chronology study of lacustrine deposits of the Upper Dingqing Formation in the Lunpola Basin, Central Tibet, it has been determined that the geological period is middle Miocene (15-12 Ma). Stable isotope and palynological records indicate a climatic transition around 13.8 Ma, characterized by cooler and drier climate. New palynological elevation reconstructions suggest a maximum paleo-elevation of 3100-3600 m (average 3350 m) for the Lunpola Basin, consistent with floating-leaf plants data. This study provides new insights into paleoenvironmental reconstructions and paleo-elevation estimates of the Lunpola Basin, Central Tibet.