Paleomagnetic and Fission-Track Dating of a Late Cenozoic Red Earth Section in the Liupan Shan and Associated Tectonic Implications  

作　　者：李云 宋友桂 千琳勃 李小明 强小科 安芷生 

机构地区：[1]State Key Laboratory of Loess and Quaternary Geology, Institute of Earth and Environment, Chinese Academy ofSciences [2]University of Chinese Academy of Sciences [3]School of Geography, South China Normal University [4]Key Laboratory of Marginal Sea Geology, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences

出　　处：《Journal of Earth Science》2013年第4期506-518,共13页地球科学学刊（英文版）

基　　金：supported by the National Natural Science Foundation of China (Nos. 41290253, 40772116);the National Basic Research Program of China (973 Projects) (Nos.2010CB83340, 2013CB955904)

摘　　要：The north-trending Liupan Shan （六盘山） is an important tectonic boundary between the Tibetan Plateau and the Ordos platform. The Late Cenozoic red earth deposits of the Liupan Shan record its tectonic history and environmental effects. In this article we report a new Late Cenozoic red earth section from an intermontane basin in the southern part of the Liupan Shan. Lithofacies analysis, paleomagnetic and fission-track chronologies, and paleocurrent analysis have been employed to identi- fy the tectonic uplift events of the Liupan Shan. Based on the age constraints of mammal fossils, the pa- leomagnetic polarity zones of the Huating （华亭） Section can be approximately correlated with the standard polarity zones that lie between C3An.2n and C5n.ln of the Geomagnetic Polar- ity Timescale; the bottom age of this section is approximately 10 Ma. Based on this and the previous studies, we infer that a tectonic event commenced in the southern Liupan Shan in this interval between 8.3 and 8.7 Ma, accompanied by a remarkable increase in sediment accumulation rate. Field observations, fission-track dating, determinations of grain-size frequency distribu- tions and the vertebrate fossils found there suggest that the red earth deposits were reworked by water and mainly transported by fluvial-alluvial processes from the adjacent area.The north-trending Liupan Shan （六盘山） is an important tectonic boundary between the Tibetan Plateau and the Ordos platform. The Late Cenozoic red earth deposits of the Liupan Shan record its tectonic history and environmental effects. In this article we report a new Late Cenozoic red earth section from an intermontane basin in the southern part of the Liupan Shan. Lithofacies analysis, paleomagnetic and fission-track chronologies, and paleocurrent analysis have been employed to identi- fy the tectonic uplift events of the Liupan Shan. Based on the age constraints of mammal fossils, the pa- leomagnetic polarity zones of the Huating （华亭） Section can be approximately correlated with the standard polarity zones that lie between C3An.2n and C5n.ln of the Geomagnetic Polar- ity Timescale; the bottom age of this section is approximately 10 Ma. Based on this and the previous studies, we infer that a tectonic event commenced in the southern Liupan Shan in this interval between 8.3 and 8.7 Ma, accompanied by a remarkable increase in sediment accumulation rate. Field observations, fission-track dating, determinations of grain-size frequency distribu- tions and the vertebrate fossils found there suggest that the red earth deposits were reworked by water and mainly transported by fluvial-alluvial processes from the adjacent area.

关 键 词：red earth MAGNETOSTRATIGRAPHY PALEOCURRENT fission-track dating Liupan Shan. 

分 类 号：P542[天文地球—构造地质学] P534.63[天文地球—地质学]