摘要:
沉积中心呈左行斜列,等厚线呈卵形封闭,三组走滑断裂系统影响和控制沉积及火山岩盆地的发育和分布,盆地呈菱形并以拉分性质为主,盆地中的地层层序显示内新外老的环形扩张结构,以及岩浆活动强烈等特征表明:下扬子区侏罗纪-早白垩世为一走滑引张盆地.进一步的研究将其分为两个演化阶段:碎屑沉积为主的早期阶段(J1+2)和岩浆活动为特征的晚期阶段(J3~K1).
Abstract:
The left-oblique depocenter,the oval enclosed isopsach,sedimentary and v olcanic basins controlled and influenced by three sets of strike-slip faults,th e rhombus basins where the circular extentional structure with respect to the st rata young inside and old outside,all of them prove that from the Jurassic Perio d to the Early Creatceous Epoch the transextensional basin was formed in the Lo wer Yangtse Region.Further research showed that its evolution can be divided int o 2 stages,i.e.,early stage(J1+2) featured by clastic sedimentation and t he later stage (J3-K1) in the property of intensely magmatic activity. In the extensional background of Mesozoic in Eastern China,three sets of strike -slip faults were developed.They are:1)Yangtse Fault,also as zigzag fault,2)bra nch faults obliquely jointed with Tanlu Fault,which cut the main part of the Low er Yangtse Region into wedge-shaped blocks;3)the horse tail-shaped faults taki ng the Qingyang-Guangde Fault as its main component,the later also as the south ern limit of the Lower Yangtse Region.The faults controlled the formation and ev olution of basins. In the Lower Yangtse Region,the basins were classified into 3 types.They involve :1)sedimentary basin, e.g. Susong Basin, Caohan Basin, 2)sedimentary-volcanic basin, e.g.Ningwu Basin,Luzong Basin,3)volcanic basin formed laterly,e.g.Lishu i Basin,Liyang Basin and Fanchang Basin.Among them,Luzong Basin and Ningwu Basin were proved to be typical pull-apart basins,where the strata were arranged seq uentially,i.e.from center to margin,they become older.The basin is of circular e xtensional structure in plane.The laterly formed volcanic basins as rhombus are strike-slip basins. The sedimentary center of J1+2 were left-obliquely arranged in equal spa cing intervals.The main sedimentary centers were just above the NNE parts of Yan gtse Fault.The concordance of sedimentation with structure revealed that the fau lt controlling the distribution of sub-lift and sub-settlement in basins.