华北地区三叠纪盆地格局及演化分析

三叠纪是华北地区构造格局的重要转型期,该时期发生的印支运动影响着华北地区盆地的发育演化.早—中三叠世,华北板块内部基本继承了晚海西期以来的构造格局和沉积特点,地势北西高、东南低,为一南陡北缓、呈NWW向展布的大型内陆沉积盆地,恢复的地层原始沉积厚度在1 500～2 000 m之间.晚三叠世扬子板块与华北板块之间发生自东向西的剪刀式碰撞拼接,华北地区发生全面抬升,且东部抬升早、抬升幅度大,西部抬升晚、抬升幅度小,沉积盆地的范围向西发生退缩.华北地区西南部仍为统一的大型沉积盆地,发育温暖潮湿气候下的河流、湖泊、沼泽相沉积;华北东部大部分地区处于隆升剥蚀状态,使得先期沉积的早—中三叠世地层发生剥蚀,一些地区剥蚀作用深至古生界,仅局部地区发育小型山间盆地沉积.

Basin pattern and evolution of Triassic in North China

Triassic is an important transition period in the structural evolution of North China.The basin pattern and evolution of Triassic in North China is discussed based on the study of the development characteristics of the residual strata of the Triassic.It is held that the Indosinian movement happening during Triassic is the dominant factor of the basin evolution in North China.From the Early Triassic to the Middle Triassic,there possibly exists a large-scale NWW-trending sedimentary basin in the North China Plate,which presents steeper in the south and gentler in the north,and higher in the northwest and lower in the southeast.The evolution of the basin inherits the structural and sedimentary pattern in late Hercynian.The original thickness of Lower and Middle Triassic is 1 500~2 000 m.During late Triassic,the scissors-type collision splicing occurs between the Yangtze Plate and the North China Plate,which leads to the uplifting of the North China Plate.The uplifting is heterogeneous:the uplifting in the east is earlier and higher than that in the west.And the basin retracts to the west:there is still a basin in the west of North China,there developed the sediments of fluvial-lacustrine facies under the warm and humid climate,but its scale become smaller compared with the basin in Early--Middle Triassic;in the eastern most areas of North China,the strata of the Lower and Middle Triassic are denuded,and even some strata of the Paleozoic are also denuded.There developed small-scale intermountain basin sediments only in the eastern local areas of North China.