青藏高原中部温泉盆地西侧晚第四纪正断层作用的地貌标志及断裂活动速率  

Geomorphologic indicators and rates of late Quaternary normal faulting at the west side of the Wenquan graben, central Qinghai-Tibet Plateau,

作　　者：吴中海[1] 吴珍汉[1] 胡道功[1] 马志邦[2] 叶培盛[1] 刘琦胜[1] 尹功明[3] 

机构地区：[1]中国地质科学院地质力学研究所,北京100081 [2]中国科学院地质与地球物理研究所,北京100029 [3]中国地震局地质研究所,北京100029

出　　处：《地质通报》2005年第1期48-57,共10页Geological Bulletin of China

基　　金：中国地质调查局项目<青藏铁路沿线活动断层调查与地应力测量>(批准号1212010340302);<西藏1:25万当雄幅区域地质调查>(批准号DKD9901001)成果。

摘　　要：温泉盆地西缘断裂在晚第四纪期间经历了多期活动。沿断层至少可以识别出高度分别为0.33～0.62m、4.3～5.2m、6.8～8.3m、10～11.8m、约16m、20～28m、45～50m和65～80m的8套断层崖或断层陡坎,以及与各级断层崖大致对应的河流阶地、洪积扇和泉华台地。地质地貌体的相对时代分析和泉华、河流沉积物中的砾石钙膜、钙质胶结物的U系、ESR测年结果表明,高45～50m、20～28m、约16m、10～11.8m、6.8～8.3m和4.3～5.2m的断层崖可能分别形成于约127kaBP、54kaBP、25kaBP、18kaBP、11kaBP和4kaBP以来或更早。综合分析断裂不同地点的断层崖的高度和时代发现,不同时期的断裂活动强度可能是不同的。其中在约127～25kaBP、25～4kaBP期间,断裂平均的垂直活动速率分别为0.3～0.23mm/a、0.8～0.36mm/a,而约4～1.1kaBP期间的断层最大垂直活动速率可能达1.65mm/a。Surface observations along the nearly N-S-trending Western Wenquan basin marginal fault in the interior of the Tanggula Mountains show that this fault underwent multi-stage activities during the late Quaternary. Along the fault we may recognize at least eight fault scarps or steep fault slopes whose heights are 0.33-0.62 m, 4.3-5.2 m, 6.8-8.3 m, 10-11.8 m, ～16 m, 20-28 m, 45-50 m and 65-80 m respectively, as well as river terraces, diluvial fans and spring sinter platforms that may largely correspond with these fault scarps. Analysis of the relative ages of geologic-geomorphologic bodies and U-series and ESR dating of calcareous coatings of pebbles and calcareous cements in spring sinters and stream sediments indicate that the fault scarps with heights of 45-50 m, 20-28 m, ～16 m, 10-11.8 m, 6.8-8.3 m and 4.3-5.2 m formed at ～127 ka BP, 54 ka BP, 25 ka BP, 18 ka BP, 11 ka BP and since 4 ka BP. The intensities of faulting were different in different periods. The average rates of vertical movements of the fault during ～127-25 ka BP, 25-4 ka BP and 4-1.1 ka BP were 0.3-0.23 mm/a, 0.8-0.36 mm/a and 1.65 mm/a respectively.

关 键 词：青藏高原 温泉地堑 晚第四纪 正断层作用 东西向伸展变形 

分 类 号：P546[天文地球—构造地质学]