Abstract:

Hujiagang is located in Yingxian, Shanxi Province. The river terrace in Hujiagang was formed between 66.46 ka and 33.62 ka. The grainsize distribution characteristics were used to interpret the deposit environment of Hujiagang river terrace. The grainsize distribution characteristics show the following four aspects: (1)the grain sizes of strata in Hujiagang river terrace upwardly change from coarse to fine with a positive rhythm sedimentary characteristics，and the strata can be sorted into four sections, ie A, B, C and D;(2)sediments in section A which mainly consist of fine sands have similar grainsize distribution characteristics and were mainly transported in saltation, showing asymmetrical single hump and two parts in probability accumulation curves, and the sorting is good, indicating that the hydrodynamic activity is strong and the deposit environment is stable; (3)sediments in sections B and C which mainly consist of fine sands and silts have different grainsize distribution characteristics and are mainly transported in saltation, showing asymmetrical two humps and two parts in probability accumulation curves, and the sorting is bad, indicating that the hydrodynamic activity is strong and the deposit environment is instable; (4)sediments in section D which mainly consist of silts have similar grainsize distribution characteristics and are mainly transported in suspension, showing asymmetrical single hump and two parts in probability accumulation curves, and the sorting is good, indicating that the hydrodynamic activity is weak and the deposit environment is stable. The strata in Hujiagang river terrace in general are formed in fluvial facies and the top is alluvial plain sediments. The change of these grainsize distribution  characteristics is in accord with the oxygen isotope variation of Guliya ice core, thus the change of grain size and the deposit environment of Hujiagang river terrace are controlled by the climate change.

Key words: river terrace, grain size characteristic, deposit environment；climate change, Hujiagang, Shanxi