摘要 在野外调查的基础上,分析汉江郧阳段河流阶地的发育特征。结合地质、地貌及第四纪测年学资料,推断汉江T1~T5阶地形成的时代分别为全新世-晚更新世末期(约25 ka BP)、晚更新世(约67 ka BP)、晚更新世早期-中更新世末期(约128 ka BP)、中更新世早期-早更新世晚期(约1 344 ka BP)、不晚于早更新世。阶地的横向对比显示,两陨断裂的活动导致汉江五峰段、青曲段、郧阳盆地段T3、T2阶地在垂向上构造隆升的差异性,结合T3、T2阶地的形成时代,推测断裂活动的时代为中更新世末期-晚更新世早期。近似地推算汉江郧阳段更新世早期以来的平均隆升速率约为0.052 mm/a,显示抬升速率及幅度较秦岭弱,可能由于汉江郧阳段处于秦岭东南缘余脉,并非秦岭隆升的中心地域。
Abstract:The characteristics of the Hanjiang river terraces in Yunyang part are investigated in the field work. With geological, geomorphological and Quaternary chronological data, we infer that T1-T5 terraces were respectively formed in Holocene-late Pleistocene (about 25 ka B P), the late Pleistocene (about 67 ka B P), the early late Pleistocene-the end of middle Pleistocene (about 128 ka B P), the early middle Pleistocene-the late early Pleistocene (about 1 344 ka B P), no later than early Pleistocene. Horizontal contrast of terraces show activities of Liangyun fault make the vertical differences, indicating uplift between the T3 and T2 terraces from Wufeng, Qingqu and Yunyang basin. We suggest the age of faulting is the end of middle Pleistocene-the early late Pleistocene according to the forming age of the T3 and T2 terraces. The average uplifting rate of Hanjiang terrace in Yunyang part since the early Pleistocene is about 0.052 mm/a, which shows that the uplifting rate and magnitude is weaker than that in Qingling mountain. The main reason may be that Yunyang is located in the southern margin of Qinling mountain but not the center raising area.