Geographical Research, Volume. 39, Issue 6, 1242(2020)
Studying river terrace is an important way to explore regional evolution of hydrology, paleoclimate and geomorphology. There is few reports about terraces of Guizhou because intense weathering results in poor profile preservation in this area. In Wudang Basin, a typical intermountain basin located in central Guizhou, Neotectonic movement resulted in a well-preserved sequence of four terraces, which indicates the regional crustal uplift and basin evolution clearly. In this article, measurements on gravel fabric and grain size of sediments are used to analyze the sedimentary environment of terraces. And then, combined with optical luminescence (OSL) dating, the discussion is focused on evolution age and process of Wudang Basin. The results show that in the study area, the gravels are poorly sorted and varying roundness but well orientated with river flows. The fact that lithology of gravels possess distinct inheritance indicates that they come from the surrounding stratum. Based on the gravel fabric analysis, it is concluded that the basin experienced an intense erosion during tectonic uplift. Grain size measurements on floodplain sediments present that dynamics of the rivers have an increasing tendency, which indicates regional climatic changes during a relatively tectonic stable stage. In stages of T4 and T3, there was erosion and denudation in Wudang Basin, which formed the embryo of the modern geomorphology. OSL dating shows that the age of T2 terrace is from 177.4 ka to 87.6 ka, which is consistent with the last interglacial in the sequence of Chinese glaciations and MIS5 (125 to 75 ka). So it is held that in stage of T2, warm and humid climate was important for terrace deposit up to a 10-m thickness. Based on sediment characteristics and time series, it is believed that at the late stage of Middle Pleistocene, there was a sedimentary leveling lasting for tens of thousands of years before Wudang Basin basically formed. The age of T1 terrace is about 25 ka, indicating the last tectonic uplift of Guizhou and the final shaping of Wudang Basin.
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Xi JIANG, Wenqi CHEN, Fan NING, Jun ZHENG, Weijun LOU, Yong ZHOU.
Received: Jun. 24, 2019
Accepted: --
Published Online: Oct. 9, 2020
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