滇西哀牢山-点苍山形成的构造和地貌过程*

青藏高原东南边缘规模最大的一条新生代走滑剪切带沿云南滇西的哀牢山-点苍山山脉分布。构造和地貌证据表明,该山脉的形成可能经历了4个阶段:第1阶段发生在中新世早中期(22~17百万年),以差异性大规模的隆升为特征,同时伴随着剥蚀,成因是剪切带的左行走滑运动;第2 阶段发生在20~10百万年,以区域性侵蚀为特征,山体的大部分与周边地体同时被夷平;第3阶段发生在中新世中晚期(13~9百万年),以区域性隆升和河流快速下切为特征,差异性的侵蚀导致山体雏形的形成;第4阶段始于晚新生代(5百万年),以差异性隆升为特征,其中, 点苍山的隆升是构造成因, 而哀牢山山体的形成可能与红河的下切相辅相成,有限的隆升是地壳发生均衡反弹造成的。

DEFORMATIONAL AND GEOMORPHIC PROCESSES IN THE FORMATION OF THE AILAO SHAN-DIANCANG RANGE,WEST YUNNAN

Much of Cenozoic intracontinental deformation of the southeastern part of the Tibetan Plateau was accom￣modated by strike-slip fault systems, the largest being the Red River-Ailao Shan shear zone, marked by the Ailao Shan-Diancang Shan Range in central Yunnan, China. The structural and geomorphic evidence demonstrate that the evolution of this mountain range can be divided into 4 stages. The first stage occurred in Oligocene-Miocene time (22~17Ma), dominated by large-scale differential uplift coeval with erosion, caused by left-lateral strike slip movement. The second stage took place during 20~10Ma, in which the mountain range and the adjacent area were eroded into a landform with low relief. The third stage occurred in Mid-Late Miocene time (13~9Ma), featured by regional uplift coeval with incision of the river systems, by which the embryonic form of the mountain range emerged. The last stage occurred in Late Cenozoic time (ca.5Ma), dominated by differential uplift, caused by extension and isostasy due to change in climate.