Liaoning Southwest Jurassic Inverse Red Nappe Tectonic Deformation Process

Syntectonic sedimentation analysis is a new approach, which has been developed and implemented for more than 30 years, for studying regional tectonic deformation. Thrusting and related folding will result in the uplift of the hanging wall of a thrust fault. Detritus shed from uplifted area tend to be transported and deposited into the foreland basin or foredeeps in front of the thrust belt. Any variations in the rate of the thrusting could be recorded in this syntectonic/synkinematic sedimentations. All of mentioned above consists a theoretic foundation for the syntectonic sedimentation analysis. By analysing the sedimentary sequence, we can learn how the thrust faulting and related deformation might have happened during geologic history. By using syntectonic sedimentation analysis method, on the base of a lot of field survey and indoor analysis on sand-size sedimentary rocks we carried out a lot research on Jurassic syntectonic sedimentation, and its relation to the structural deformation in southwest Liaoning province. Several pieces of new achievement and fresh understandings have been arrived as fellows: 1.It has been found that there are two series of syntectonic sedimentation in the research area. They are Early Jurassic Dengzhangzi Formation in Niuyingzi-Guojiadian Basin and Early Cretaceous Jingangshan Formation in Jianchang Basin respectively. They are characterized by huge-layered conglomerates and breccias, which mainly consisted of limestone and dolomite gravels. 2.Gravels existed in Dengzhangzi Fm emerged from lower to upper with the order of andesites, quartzites, limestones, dolomites and diabase. The source strata of them are Shuiquangou Fm, Triassic-Carboniferous, Cambrian-Ordovician, Jixian System and diabase sill in Xiamaling Fm respectively. An unroofing process of a normal sequence of source strata has been revealed. Provenance analysis show gravels come from west of the basin. The structural characters of the western area of the basin indicate that Huangjindaishan-Dameiling Thrust Fault was supposed to be the control fault of syntectonic sedimentation and Houzhangzi-Dameiling Anticline was caused by the thrust fault. This anticline consists of the source area for the Dengzhangzi Fm syntectonic sedimentation. The Dengzhangzi Fm. is not a foredeep sedimentation in front of a large-scale top-to-the-west thrust fault as proposed previously by other geologists. 3. It is proposed that the Hekanzi-Nangongyingzi Thrust Faulting be responsible for the formation of the syntectonic sedimentation of Jingangshan Fm in Jianchang Basin. Distribution of the conglomerates and the variations in size of the detritus in Jingangshan Fm illustrate that when the northeast segment of the thrust fault was keeping moving the southwest segment remains stable. It is possibly that several minor thrust faults developed in front of main fault controlled the syntectonic sedimentation. Provenance of syntectonic sedimentation was eroded away after the thrusting deformation otherwise the thrust fault would have reached the location where now syntectonic sedimentation is located. 4.By combining the results of previous investigations on the thrust faults and the syntectonic sedimentation data acquired in this research, a three-generation thrusting sequence during Jurassic period has been established. The first occurred after Early Jurassic Guojiadian Fm, represented by Great Wall System thrusting upon the volcanic rocks; the second occurred after Early Jurassic Shuiquangou volcanic eruption events, represented by syntectonic sedimentation overlied; the third occurred after Middle Jurassic Tiaojishan volcanic eruption events, represented by Wumishan Fm thrusting upon the volcanic rocks.