Development of the alluvial and lacustrine terraces on the northern margin of the Hetao Basin, Inner Mongolia, China: Implications for the evolution of the Yellow River in the Hetao area since the late Pleistocene

Terrace formation processes can reflect the evolution of large rivers. The Hetao Basin is a floodplain of the Yellow River, and there are two to three terraces that extend E–W on the northern margin. Based on a detailed field geological survey and measurement of the terrace sections, combined with sedimentological and chronological analyses, we reconstructed the developmental processes of the three terraces and inferred that three river terraces were formed by the Yellow River. The OSL dating results show that the time of deposition of terrace 3 was prior to 118kaBP. Subsequently, the terrace began to experience incision and formed the geomorphic surface of terrace T3. Similarly, terrace 2 and terrace 1 were mainly deposited from ~109 and 59ka, respectively; and began to be incised prior to 71 and 46ka, respectively. The three terraces in the northern Hetao Basin are the products of the combined actions of climatic shifts and tectonic uplift. The Yellow River's evolutionary history in the Hetao area since the Late Pleistocene is discussed. Before about 120kaBP, the Yellow River may have flowed through the northern Hetao Basin. Between 110 and 70kaBP, the Yellow River experienced at least two changes between river and lake sedimentation. From 60 to 50ka, a very large river-connected lake of the Yellow River was developed in the Hetao Basin. After 50ka, the Hetao river-connected paleolake of the Yellow River gradually dried.