The evolution of a terrace sequence along the Yellow River (HuangHe) in Hequ, Shanxi, China, as inferred from optical dating

Abstract

Investigations of river terraces are often seriously hindered by difficulties in dating the formation of terraces using conventional and well-established methods such as 14C dating. In this paper, recently developed optical dating techniques were applied to a Yellow River terrace sequence in the Hequ area, Shanxi Province, China. Based on field investigations, four terraces were identified. Systematic sampling for optical dating was carried out on these terrace deposits. The single-aliquot regenerative-dose method was used to determine equivalent dose. By analyzing the degree of bleaching of fluvial samples, maximum and minimum optical ages were obtained for these samples. The minimum optical dates obtained are geomorphologically and stratigraphically consistent with each other, suggesting that the dates are reliable. The formation ages of the four terraces are 3.4 ∼ 10, 20 ∼ 25, ∼ 30 and ∼ 90 ka, respectively. On the basis of these optical dates, the geomorphological evolution of the terrace sequence was established, and the factors affecting the terrace development discussed.