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通过对汉江上游湖北郧县-郧西段河谷的野外考察,选择前坊村汉江第一级阶地典型的黄土覆盖层剖面进行了深入研究。我们系统进行采样,分选出40～63μm石英颗粒,利用单片再生剂量法(SAR)技术,测得这些样品的光释光(OSL)年龄在2.90±0.15～16.76±0.60ka之间。OSL年龄值与地层深度表现出良好的对应关系。其中,利用释光信号组分拟合得到3种指数组分,发现快速组分达80%以上,且不同积分区间获得的D_e值处于一个坪区,各测片D_e值呈正态分布,说明这些风成沉积物晒退比较彻底。结合粒度参数Y值分析,确定这些沉积物属于风成堆积物。利用样品OSL年龄与气候替代指标,结合与秦岭北侧黄土剖面的对比,表明汉江上游河谷第一级阶地的风成堆积物从18.0ka开始堆积形成。自全新世以来受到不同程度的成壤改造作用,形成了与渭河谷地相似的L_1-L_t-S_0-L_1-MS土壤地层序列。同时发现在1.8ka(200A.D.)前后,汉江上游发生了一期特大古洪水事件。这些研究成果对于深入了解汉江上游水文气候变化具有重要意义。
Through the field investigation of the Yunxian-Yunxi section of the upper reaches of the Hanjiang River, the typical loess cover section of the first terrace of the Hanjiang River in Qianfang Village was selected for further study. We systematically sampled and sorted out 40 ~ 63μm quartz particles. The OSL values of these samples were measured between 2.90 ± 0.15 ~ 16.76 ± 0.60ka using single-cell regeneration dose method (SAR). OSL age value and the depth of strata showed a good correspondence. Among them, three exponential components were obtained by fitting the luminescence signal components, and the fast component was found to be more than 80%. The D_e values obtained in different integration intervals were in a plateau area and the D_e values were normal distribution These winds and sediments sun drying more thoroughly. Combined with the grain size parameter Y value analysis, it is confirmed that these sediments belong to the wind accumulation. Using the OSL age and climate substitution indices of the samples and the comparison with the loess profiles on the northern side of the Qinling Mountains, it shows that the aeolian deposits of the first terrace in the upper reaches of the Hanjiang River started to accumulate from 18.0 ka. Since the Holocene, it has been affected by the process of pedogenesis and reformation, forming a series of L_1-L_t-S_0-L_1-MS soil strata similar to the Weihe valley. Also found in the 1.8ka (200A.D.) Before and after the occurrence of a major flood in the upper reaches of the Han River. These findings are of great significance for understanding the hydrological and climate changes in the upper reaches of the Hanjiang River.