Temporal and Spatial Distribution of the Late Devonian (Famennian) Strata in the Northwestern Border of the Junggar Basin,Xinjiang,Northwestern China

The base of the Saerba Member(Mbr) of the Hongguleleng Formation(Fm.) probably lies in the Famennian Palmatolepis crepida Zone;the Longkou Mbr is probably a sedimentary wedge that thins out northwards;the Duguer Mbr has an approximate age from the upper part of the Pa.marginifera Zone or the Lower Pa.rugosa trachytera Zone through the top of the Pa.perlobata postera Zone;the Wulan Mbr has an age approximately corresponding to the whole Pa.gracilis expansa Zone.In the Bulongguoer section,the Lower Mbr of the Hongguleleng Fm.corresponds to Famennian Pa.crepida Zone through Pa.marginifera Zone;the Middle Mbr probably ranges from the Pa.r.trachytera Zone through the Pa.g.expansa Zone.The basal Namu Mbr of the Heishantou Fm.is probably the product during and after the Hangenberg Event in the upper part of the Siphonodella praesulcata Zone,which is still within the Devonian.In this context,the underlying Chasi Mbr may approximately correspond to the lower part of the S.praesulcata Zone(before the Hangenberg Event).Lateral distribution of strata indicates that the Upper Devonian in the Gennaren and Saerba areas each constitutes a structure of syncline,which differs from the previous recognition of a monocline structure.