Palaeowind reconstruction from Lower Cretaceous wave-dominated depositional records of the Tanan Depression, Northeast Asia

Palaeowind regime is an important component for reconstructing palaeoclimate and understanding ancient global circulation. We applied the beach-ridge thickness technique (BTT) and the longshore-bar thickness technique (LTT) to reconstruct the Early Cretaceous palaeowind velocities based on depositional records of Tanan Depression in Northeast Asia. The thickness of beach ridges and nearshore bars is the most important parameter for applying the BTT and the LTT methods. We identified 22 beach ridges and 23 nearshore bars based on drilling cores and wireline-log data in the Tanan Depression. Palaeowind velocities calculated by using the LTT method ranged from 10.84 to 13.66 m/s, showing a narrower range than those calculated by using the BTT method (7.58–15.93 m/s). We further analyzed the underlying factors causing the difference between the results derived from these two methods based on the sedimentary process of the beach ridge and the nearshore bar. The reconstructed wind regime was assumed to be the summer monsoon originating from the Mongol-Okhotsk Ocean before it had been completely enclosed, which provides valuable insight into the understanding of the atmospheric circulation in Northeast Asia during the Early Cretaceous.