Geometry And Mechanism Of Dalianghui Anticline In Micangshan Foreland, Thrust Belt, Northern Sichuan Basin

Micangshan mountain is located in northern Sichuan basin , Micangshan mountain is adjacent to Qinling oroganic belt in the north, and closed to ark-like Dabashan Mountain in the east . There lie Songpan-Ganzhi oroganic belt and Longmen nappe in the west . Micang mountain is influenced by the three structure systems . Considering the unique structure situation and mechanical stratigraphy makes it as a very complicated oroganic belt . The paper is to anlayse the structure geometry and kinematics in Micangshan mountain foreland ,work out the stage and geological age of those structures.This paper mainly reaserchs the formation lithology in front of Micang mountain, classify the detachment in front of Micang mountain, they are : shale of Sinian , clay shale of Cambrian , gypsum of Triassic ; Using amount of cross-section identify the geometric shape of Micang mountain structure , analyse the structural feature of Micang mountain from west to east, and the change of the depth of these detachment, different structural feature is controlled by different detachment with different depth . With structure analysis of seimic profile from Micang mountain , use fault-related folding theory , indentifying the dip-domain , analysing the axial-surface , the geometric shape of the basement thrust system , and the displacement of these thrust.We do some palaeomagnetism research from late Triassic Xujiahe group to early Cretaceous Hanyangpu group , and gain the depositional time of these stratas:Xujiahe group strata'depositional time is from 227.4 Ma to 209.6 Ma;Baitianba group strata'depositional time is from 199.6Ma to 193.8 Ma;Qianfoyan group strata'depositional time is from 193.8Ma to 175.6 Ma;Shaximiao group strata'depositional time is from 175.6 Ma to 163.6 Ma;Suining group strata'depositional time is from 163.6Ma to 161.2Ma;Jianmenguan group strata'depositional time is from 144.9Ma to 140.4Ma;Hanyangpu group strata'depositional time is from 140.4Ma to 132.8Ma.Recognize the uncomformity from late Triassic to early Cretaceous through field work : uncomformity between late Triassic and early Jurassic ; uncomformity between late Jurassic and early Cretaceous , recognize the growth strata and analyse the depositional rate , finally a conclude how many stage Micangshan mountain experience and when Micangshan mountain uplifts.Use crosssection anlysing the fault displacement : fault displacement of line 2004-dlh-001 is larger than 28km, fault displacement of line TNB-04-04-118MIG is 28km, fault displacement of line cross-hb102 is 16.9km .Finally we reach a conclusion that the structure feature from west to east is complicate to simple , the displacement from west to east is large to small, the stress from west to east is intense to weak . And there are two stage in Mesozoic time,they are Indo-Chinease Epoch and Eearly Yansha Epoch.And Dalianghui anticline develops in Indo-Chinease Epoch, Tongnanba anticline in Eearly Yansha Epoch.