库车坳陷第三纪磁性地层和磁组构的研究

The Tertiary Kuche depression, also known as one of the most economically important oil and gas prospecting regions in the Tarim Basin, is a foreland basin formed by flexural subsidence resulting from the southward thrusting of the southern Tianshan. Detailed geological and geophysical studies on the Tertiary sequence of the Kuche region would provide constraints not only on the Mesozoic and Cenozoic deformation patterns, and its controlling on the formation and distribution of oil and gas of the Kuche depression, but also on the India-Asia postcollisional uplift and continental deformation of the Tianshan regions. In this thesis, the Tertiary sequence of the Kuche depression, which is composed of the upper Kumukeliemu Formation, Suweiyi Formation, Jidike Formation, Kangcun Formation, and Kuche Formation, was selected for magnetostratigraphic and anisotropy of magnetic susceptibility (AMS) study. Among a total of 697 collected sites, 688 sites gave magnetic fabric results and 686 sites yielded reliable paleomagnetic results, building up magenetostratigraphy for the Tertiary sequence of the Kuche depression. By correlating with international geomagnetic polarity timescale, the followings were concluded: 1) the time interval of the sampling sections is some 31-8.1 Ma; 2) the boundaries for Kangcun/Jidike Formations, Jidike/Suweiyi Formations, and Suweiyi/Kumukeliemu Formations are at about 13.5 Ma, 26 Ma and 29 Ma respectively; 3) the Jidike Formation might be formed in an interval between the late Upper Oligocene and middle Miocene, whereas the Suweiyi Formation was formed in the Upper Oligocene, in turn, the Paleogene/Neogene boundary is most likely to be at the bottom of the Jidike Formation in the Kuche depression; 4) the dramatic transition from the marine/lacustrine to fluvial/alluvial facies in the Suweiyi Formation and the lower Jidike Formation of the Kuche depression, which may indicate the initiation of Cenozoic thrusting in the Kuche depression, is probably occurred in the late Oligocene, i.e. at about 28-25 Ma. On the other hand, systematic differences of the AMS parameters, such as the corrected anisotropy of magnetic susceptibility, shape parameter of ellipsoids, q factors, angles between the intermediate and minimum magnetic susceptibility directions and bedding, indicate that a dramatic transition of tectonic strain is most likely to occur at about 16 Ma (middle Miocene) in the Kuche depression. Taking into account the initiation o f C enozoic thrusting in the Kuche d epression i s at about 2 8-25 M a, we argue that the intensive Cenozoic thrusting in the Kuche depression is mainly happened during a period between the late Oligocene to middle Miocene.