山西六棱山北麓晚第四纪不规则断裂作用的地貌学研究

GEOMORPHIC STUDY ON LATE QUATERNARY IRREGULAR FAULTING ALONG THE NORTHERN PIEDMONT OF LIULENGSHAN RANGE, SHANXI PROVINCE, CHINA

利用航片判读和野外核查相结合的途径确定了六棱山北麓晚第四纪时期的基本地貌单元及其形成时代，研究了六棱山北麓断裂的地貌学和构造学分段性特征，通过对断错地貌面的地形剖面的高精度实测，获得了表征六棱山北麓断裂作用时空不规则性的定量资料──晚第四纪断层滑动速率随时间的涨落特性，指出距今１．５６～０．７６万ａ时段是六棱山北麓断裂作用的强烈活跃期。

Three basic geomorphic units, which were developed in response to the climate changes during the last glaciation, are recongnized along the northern piedmont of the ENE-trending Liulengshan range from airphoto interpretations and field observations. These three units are the inter-stadial fluvial fan (S3) about 23～53 ka old, the maximum-glacial fluvial fan(S2) about 10～23 ka old and the post-glacial fluvial fan(S1) about 1～10 ka old, respectively. Five fluvial terraces(T0～T4) were also developed owing to the climatic temperature fluctuations on thousandyear scale. These geomorphic units(S1～S3) and fluvial terraces(T0～T4) are chronometrically dated by thermoluminescence.Stripped geomorphic mapping shows a natural segmentation in offset-geomorphology along the norhern piedmont fault of Liulengshan range. Six segments can be divided in the mapping areas and they are the Xifutou, Donghouzikou-Dawangcun, Xitunpu-Qiulin, Huoshilin-Qiuchangcheng, Huajialing-Xiejiayao and Longmazhuang-Xinpu segments from the west to the east, respectively. A set of quantitative data (faulting ages, vertical displacements and slip rates) are obtained from long-distance topographic profiles across the offset geomorphic units or fuvial terraces. The average Holocene vertical slip rates are 0. 43～0. 48mm/a for the Donghouzikou-Dawangcun segment, a bout 0. 45 mm /a for t he Xitunpn-Qiulin segment, and 0. 53～0. 55mm/a for the Longmazhuang-Xinpu segment. The faulting irregularity is demonstrated by temproal and spatial flucturation in vertical slip rates during the Late Quaternary. The period of 15. 6～7. 6ha B P is the main phase of intensely verical faulting along the northern piedmont of Liulengshan range.