Ordovician contourites in northern Helan aulacogen,northern China

The approach to the Ordovician contourites is based on the field outcrops and laboratory analysis for the Zhuozishan section in northern Helan aulacogen,northern China,with emphasis upon the vertical changes and lateral migration of sedimentary facies and environments of the Ordovician strata in the Zhuozishan section.The curves for accommodation spaces are constructed in the light of Fischer plots.The recognition of representative carbonate contourites and presentation of the Ordovician sequence stratagraphic model have provided one useful approach to interpreting the existence of the Helan aulacogen.The transgressive systems tracts in individual sequences should be delineated as important targets for the hydrocarbon exploration in the study area.