New discovery of Late Silurian-Carboniferous extensional structure in Tarim Basin and its geological significance
Li Yuejun1, Sun Longde2, Yang Haijun3, Zhang Guangya4, Zeng Changmin3, Feng Xiaojun3, Wen Lei1, Zhang Qiang1, Jia Tiegan1
1. Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029;
2. PetroChina Company Limited, Beijing 100007;
3. Tarim Oil-field Company, PetroChina, Korla, Xinjiang 841000;
4. Research Institute of Petroleum Exploration & Development, PetroChina, Beijing 100083
After careful seismic interpretation,Late Silurian-Carboniferous extensional structures were revealed in western Manjiaer Sag,central Tarim Basin. These extensional structures comprise many small normal faults which usually group sinistral en echelon and form 2 tenso-shear normal fault zones. Combinations of the normal faults in profile become negative flower structures and small horst-graben structures. On the basis of growth index calculation,the normal fault formed in Late Silurian,continue active in Devonian and Carboniferous,ceased at the end of Carboniferous. The peak-stage of normal fault activity is Late Silurian. Late Silurian-Carboniferous normal fault also developed in Tazhong and Tabei areas,implying that Tarim Basin was under regional extensional tectonic setting in Late Silurian-Carboniferous. The extensional structure is the result of post-orogeny stress relaxation of Kunlun Caledonian orogenic belt.