Abstract:

The Late Precambriam tidal deposits are well developed and widely distributed in North China Platform.The major evidence of tidal sedimentation in these sediments includes herringbone cross bedding,lenticular beding,wavy bedding,flaser bedding,tidal channel-fill cross bedding,reactivation surfaces,various types of ripple marks and interference ripple marks,truncated ripple marks,washout structures,rill marks,mud cracks,and penecontemporaneous deformation structures.In addition,oolites,algae and stromatolites are very significant.The depositional sequences and models of clastic tidal flat,tidal-dominated delta,ferric algal flat and oolitic bank,and carbonate tidal flat(or platform)are discussed here.Four sketch map about these tidal deposits during the early and late Changchen(the Great Wall),the Jixian,and the Qingbaikou are also given.Finally,it is supposed that these tidal deposits were mainly formed in the epeiric seas on the platform margin.