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    青藏高原东北缘岷县—武都地区构造地貌演化与高原隆升

    Tectono-morphological evolution of the Minxin-Wudu area on the northeastern margin of the Qinghai-Tibet Plateau and plateau uplift

    • 摘要: 提要:西秦岭武都—岷县地区位于青藏高原东北缘,是中国两大构造地貌单元的转换过渡带。构造地貌研究表明,该地区发育四级夷平面,分别是Ⅰ级夷平面(山顶面)、Ⅱ级夷平面(主夷平面)和Ⅲ、Ⅳ级夷平面(剥蚀面),分别形成于K2—E3之前、3.6 Ma、2.5 Ma、1.8 Ma。主要河流发育4~7级基座阶地,并且四级及其以下低级阶地的特征具有相似性。夷平面和阶地的高程变化,指示了该地区地壳的隆升具有多阶段性和不均匀性,3.6 Ma以来平均隆升速率在0.42~0.57 mm/a,3.6~1.8 Ma是地壳快速隆升期,1.8 Ma以来隆升速度减缓,但晚更新世(0.15 Ma)以来,隆升明显加速,显示出青藏高原目前正处于新的加速隆升期。

       

      Abstract: Abstract:Located on the northeastern margin of the Qinghai-Tibet Plateau, the Minxian-Wudu area in the West Qinling is tectonically a transition zone between two major tectono-morphological units in China. Tectono-morphological study shows that four planation surfaces are developed in this area; they are planation surfaces I (mountain top surface), II (main planation surface) and III and IV (erosional surface), which formed before the Middle Cretaceous-late Paleocene and at 3.6, 2.5 and 1.8 Ma respectively. Four to seven terraces are developed for main rivers in this area, and terrace IV and those of still smaller orders in these rivers have similar characteristics. The variations in attitude of these planation surfaces and terraces indicate that the crustal uplift in the area occurred in several stages and heterogeneously:the average uplift rate has been 0.42–0.57 mm/a and the 3.6–1.8 Ma period was a stage of rapid crustal uplift; the uplift rate became low at 1.8 Ma but the uplift accelerated markedly since the late Pleistocene (0.15 Ma), suggesting that the plateau is now in a new stage of uplift acceleration.

       

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