J₃-K₁Compound And Conjunction Deformations Between The Dabashan And Xuefengshan Thrust Belts

Zigui complex fold is located in the congruent part of Dabashan arc tectonic belt andXuefengshan thrust belt,which is dome and basin,and is the result of the tectonic compoundingand coonjection. Because Zigui fold belt recorded the important imformation reflecting theinteraction of Dabashan and Xuefengshan tectonic belt, it is the ideal site of studying on thecompounding and combination process.This paper has a field research on Zigui sycline, Badong synclinorium and Xianglongshananticline in Zigui fold belt, whose hinge of fold, fold related fault，joints and stylolites are beenstructural analysis in detail,then we determine the superposition relation among them.Based onthose, we distinguished different deformation through matching by stages, then reconstruct thepaleo-stress-field during deformation stage. Then we vertify the interaction model through thestructure physical model.The result shows that Zigui complex fold experienced three stages of two periods deformationduring J3-K1: D1is that the Zigui sycline and Xianglongshan anticline was nearly EW.Ziguisycline was extensive round with the nearly upright axe and Xianglongshan anticlne was boxwith the upright axe.The related thrust fault was characteristic by thrusting from north tosouth.Those features may be related to Dabashan belt thrusting from NE to SW. D21is that Ziguisycline was superposition with hinge of nearly SN,then the sycline showed like a pan and theWulong anticline developed in the east of Xianglongshan anticline.The fold belt was dome andbasin.The Shuitianba fault related with Zigui sycline thrusted to SEE. The major stress fieldwas parallel bunchiness. And the deformation may be related with the Xuefengshan thrust beltwhcih was barriered by Huangling anticline when thrusting to NW. D22is that the nearly SNhinge of Zigui sycline bent to SW,and Badong synclinorium was arc been convex to NW,andthe western segment of the Xianglongshan anticline was superposition by the structuralfeatures.The major stress field was generally divergent to NW.This deformation may beconnected with that Xuefengshan thrusted to NW.Those sructural analysises show that Dabashan belt thrusting to NW firstly influenced thewestern Hubei,then Xuefenshan belt thrusted and broached to NW extended the region,that wasa compounding relation. The results of two structure physical models both are convergent arcon the surface which is showed by faults and fault-related fold and both are trough like folds onthe section.Especaily some faults is quite similar like the field fault such as Qiyueshan Faults ingeology.Those characteristics show that the compounding mode is right. By analysis of the regional tectonic and stratum trelationship,we could have a conclusion thatthe deformaion D1-D2deformed during J3to K1. As a result, Zigui complex fold which is prductby compounding superposition with the Dabashan thrust belt thrusting to SW and Xuefengshanthrust belt to NW, that shows upper Yangzi region experienced compounding superpositionprocess by stages during J3to K1, that is, upper Yangzi region was sujected to nearly SNtectonic process by Dabashan thrust belt precviously, then suffered from NW-SE structuralcompounding superposition by Xuefengshan thrust NW.