Paleo-lake evolution influenced by tectonic processes and climate changes in the Hetao Basin during the late Quaternary

Abstract

Exploration of paleo-lake evolution is crucial for the understanding of climatic and tectonic roles in earth surface. Previous studies mainly focused on the climatic effect on river-lake transitions and lake evolutions through lacustrine deposits, but with limited consideration of tectonic drivers, especially for the tectonic rift lakes in the Hetao area.Based on the analyses of lacustrine and fluvial piedmont terraces and a 400-m core from the northern Hetao Basin, along with the optically stimulated luminescence and detrital zircon U-Pb dating, we adopted an integrated “tectonics-climate-surface processes” approach to explore the climatic and tectonic effects on the lake evolution of the Hetao rift basin. Results show that lacustrine deposition on the piedmont terrace T1 (60–47 ka), underlying the T3 fluvial (80–60 ka), has an erosion contact with pluvial deposits at 55 ka, implying the paleo-lake formation at ∼ 80–60 ka and shrinkage at ∼ 55–47 ka. Lake formation was forced by basin depression under the tensile stress of tectonic movement, and was recharged by the Yellow River due to obstruction of the outlet at Tuoketuo caused by uplift.Lake shrinkage was due to the combined effect of basin lifting and warm-wet climate conditions that promoted outflow. A substantial decrease in the erosion base level and rapid water drainage induced by river cutting caused erosion of lacustrine deposits in the basin. The limited sedimentary space of the lake basin in early MIS 2 should be considered a factor in lake disappearance in addition to the dry climate. This study highlights that tectonic effects may be more important than climatic effects in the evolution of rift lakes near the young fold mountain belts.