【作者】 胡春生；

【导师】 潘保田；

【作者基本信息】 兰州大学 ， 自然地理学， 2006， 硕士

【摘要】 0.8Ma B.P.前后发生的中更新世革命是一次影响深远的环境变化事件,在气候变化、构造运动等方面都存在显著的反映。青藏高原在此时期也发生了关键性的抬升,使高原进入了冰冻圈。兰州盆地西邻青藏高原东北缘,同时也位于中国季风三角的枢纽地带,因此对环境变化事件的响应更为敏感。 在兰州盆地,本研究选定了两个黄河第四级阶地作为研究剖面,即五一山阶地和枣树沟第四级阶地。根据古地磁、光释光测年以及黄土古土壤系列对比,其结果显示这两个阶地形成于同一时代,其年代为0.865Ma B.P.。因此本文提出兰州盆地存在0.8Ma B.P.黄河阶地,该级阶地可能是兰州黄河对0.8Ma B.P.环境变化事件的地貌响应。同时根据五一山阶地的测定年代,本文认为兰州盆地可能并不存在0.6Ma B.P.黄河阶地,因此建议将昆仑-黄河运动的下限厘定为0.8MaB.P.。 河流阶地是研究地面抬升的最直接的地貌证据之一。根据黄土高原地区黄河阶地的形态特征和成因分析,本文认为其形成主要是地面抬升所致并且在黄河达到均衡状态下形成的,因此可以用阶地的形成来推断黄土高原的地面抬升量。根据对黄土高原地区黄河干支流0.8Ma B.P.阶地的研究,本文证实了黄土高原在0.8Ma B.P.前后发生过一次大范围的地面抬升,并由此导致黄河干支流发生普遍下切而形成阶地。同时根据黄土高原地区四个地点黄河阶地发育特征的分析,本文推算出黄土高原0.8Ma B.P.以来的地面抬升存在明显的时空特征,空间特征表现为地面抬升幅度有西大、东小的规律,而时间特征表现为地面抬升速率有后期加速的趋势,特别是晚更新世以来。更多还原

【Abstract】 MPR(Mid-Pleistocene Revolution) that occurred at about 0.8Ma B.P. is a significant event of environment change, which is obviously responded by climate change, tectonic movement, etc.. A decisive uplift occurred on the Qinghai-Tibetan Plateau in this period, which made the Qinghai-Tibetan Plateau enter cryosphere. Since the Lanzhou Basin adjoins the Northeastern margin of the Qinghai-Tibetan Plateau, and also lies at the key location of China’s Monsoonal Triangle, it is more sensitive in responding to the events of environment change.In the Lanzhou Basin, two fourth terraces of the Yellow River are selected as the study sections, namely the Wuyishan terrace and the fourth terrace of the Zaoshugou. Based on paleomagnetic dating, optically stimulated luminescence dating and loess-paleosol sequence matching, the result indicates that the two terraces have the same age, and both were formed at about 0.865Ma B.P.. Thus, this paper advances there is the terrace of the Yellow River at 0.8Ma B.P. in the Lanzhou Basin, and the fourth terrace of the Yellow River may be a geomorphic response to the event of environment change at 0.8Ma B.P.. Meanwhile, in view of the determined age of the Wuyishan terrace, it is improbable that there is the terrace of the Yellow River formed at 0.6Ma B.P. in the Lanzhou Basin. Therefore it is proposed that the Kunlun-Huanghe Movement might terminate at 0.8Ma B.P..River terrace is one of the direct geomorphic evidences of surface uplift. By analyzing the characteristics of terraces of the Yellow River in the Loess Plateau, it is concluded that the terraces are mainly tectonic genesis, and developing after the Yellow River reached a quasi-equilibrium state. So, it is reasonable to use terraces of the Yellow River for representing the surface uplift of the Loess Plateau. According to terraces of the Yellow River and its tributaries at 0.8Ma B.P. in the Loess Plateau, thispaper verifies that there was a large-scale surface uplift at about 0.8Ma B.P. on the Loess Plateau, and the surface uplift resulted in river incision and terrace formation. At the same time, based on the characteristic analysis of the terraces at the four sites on the Loess Plateau, it is suggested that the surface uplift of the Loess Plateau since 0.8Ma B.P. has obvious spatial and temporal features. The spatial feature is that the surface uplift of the Western Loess Plateau is more intense than that of the Eastern Loess Plateau, and the temporal feature is that the uplift gradually speeded up, especially since the late Pleistocene.更多还原