【作者】 刘勇；

【导师】 李吉均； 赵志军；

【作者基本信息】 南京师范大学 ， 第四纪地质学， 2006， 硕士

【摘要】 野外地质地貌调查和对川西高原DEM的分析结果表明，川西高原存在两级夷平面和一级剥蚀面。较高的一级海拔5100m左右，分布在山脉的顶部，称山顶面；较低的一级海拔4500-4300m左右，分布广泛，成都盆地西缘大邑砾岩、炉霍盆地砾岩和松潘盆地文家祠组砾岩反映此夷平面的解体，时代约在3.6Ma前后。剥蚀面作为宽谷分布在现代水系谷地外围，成为谷肩，在宽谷面以下发育深切峡谷。这些峡谷中发育有一系列的河流阶地。经过野外调查，我们查明了川西高原主要河流(岷江、大渡河、青衣江、鲜水河等)在特定河段的阶地序列，并主要应用ESR(电子自旋共振)法测定了河流阶地的形成年代。结果表明，杂谷脑河理县段共发育八级阶地，各级阶地拔河高度分别为7、17、37、60、102、210、262和312m，T2、T3、T4、T5和T6阶地的形成年代分别为54、125、248、313和481ka；大渡河泸定段共发育七级阶地，各级阶地拔河高度分别为10、50、100、770、820、880和950m，T1-T7阶地的形成年代分别为9.34、32.18、104.05、680、756、842和1130ka；鲜水河炉霍段共发育十二级阶地，各级阶地拔河高度分别为5、15、45、125、165、175、230、255、265、295、335和365m，T5、T9、T10、T11和T12阶地的形成年代分别为93.5、261、384、462和598ka。测年结果表明，川西高原主要河流阶地均形成于更新世以来。这些阶地在形成时代上具有较好的一致性。阶地成因分析表明这些主要河流阶地序列主要是区域构造隆升的结果，气候变化(冰期—间冰期旋回)起辅助作用。因此，各河流主要阶地分别代表了区域性的构造隆升事件，反映了川西高原第四纪隆升的整体性。由阶地高程和阶地形成年代计算得出的杂谷脑河、大渡河、鲜水河更新世以来的下切速率分别为0.37m／ka、0.38m／ka和0.39m／ka。自高原边缘的杂谷脑河到高原内部的鲜水河，平均下蚀速率呈现出微小的增加趋势，这在一定程度上也指示了高原边缘向高原内部构造抬升强度呈现微弱的增强趋势。更多还原

【Abstract】 Field observation and analysis of the DEM of Western Sichuan Plateau indicate that, there are two planation surfaces and one erosion surface in Western Sichuan Plateau. The higher planation surface about 5100m in height is only preserved on the crest of the mountains, so called the summit surface; the lower one about 4500-4300m in altitude is well preserved over the plateau, so called the main planation surface. This widely distributed surface was dissected by an intensive tectonic activity around 3.6 Ma, as indicated by the deposition of Dayi conglomerate in Western rim in Chengdu Basin, Luhuo conglomerate in Luhuo Basin, and Wenjiaci conglomerate in Songpan Basin. An erosion surface (pediment) gently tilted towards the modern drainage system, is identified below the main planation surface. This pediment is deeply incised to form V-shaped valley. Several fluvial terrace sequences within the V-shaped valley at upper reach of Minjiang, the Zagunao River at Lixian, the Xianshui River at Luhuo, and the Dadu River at Luding, were identified and dated applying ESR method. The result shows that all the terraces were developed during the Middle Pleistocene, and some of them, synchronously. The development of these terraces on Western Sichuan Plateau is prominently under the control of tectonic uplift, and climate change , such as glacial and interglacial circle , plays a assitant role in the forming of the river terraces , so the river terraces have recorded the coherently phased rise of the plateau during Quaternary. The incision rates of Zagunao River、 Dadu River and Xianshui River were 0.37m/ka, 0.38m/ka and 0.39m/ka respectively, from the plateau margin to the interior, the incision rate has a slight increasing trend , to some extent, we can say that, from the margin to the interior , the uplift intensionof the plateau has a slight increasing trend.更多还原