河北省怀来县晚三叠世冲积扇及其构造环境

河北省怀来地区发育一套由角砾岩组成的类磨拉石建造。角砾岩的角砾成分可分为三层，它们分别来自于新元古代长龙山组，古生代馒头组与张夏组，它们的堆积顺序与本区地层顺序完全一致，这种与“重矿物反剖面”原理相违背的地层序列反映了它形成于特殊的构造背景，根据岩层上下的接触关系，植物饱粉及上覆地层的同位素年龄等特征，可确定为晚三叠世杏石口组，研究表明，这套沉积是在印支运动背景下，受北东上黄旗－乌龙沟深大断裂控制

The Late Triassic Alluvial Fan of Huailai County,Hebei and its Structural Environment

The quasi molasse suite found in the Huailai area of Hebei is compossed of breccia It may be divided into three beds according to the components breccia They came respectively from the Changlongshan formation of Neo Proterozoic Era,and Mantou formation and Zhangxia formation of Palaeozoic Era The accumulational order of the components are concordant with the stritigraphic successions in the area This kind of phenomenon that shows quite the contrary with the principle of inverse section of heavy mineral reflects the special structure background of its formation According to the contact relationship of rock bedding,the sporepollen and the isotopic age of overlying strata and so on,we affirm that is the Xingshikou formation of late Triassic Epoch Study shows that the deposits as a quasi molasse suite were formed by the geological process of retrogressive erosion and controlled by the Shanghuangqi Wulinggou deep faults basin under the backgrornd of Indo Sinian movement The quasi molasse suite may be divided into two sedimentary sequences of alluvial fan They respectively consist of debris flow facies,sieve deposit facies,sheet flood facies,stream channel facies,limnetic facies and so on The evolution of sedimentary basin underwent three stages,i e folding stage,basin formed stage and deposit stage This evolution modle will have important guiding sense to the study of Triassic system in Yanshan area