Study Of Sequence Stratigraphy And Sedimentary Facies Of The Ordovician In Yubei Area

Based on rock and biostratigraphy,Jade North Tarim Basin Ordovician sequence stratigraphy three isochronous grid planes has been established though the Ordovician sequence analysis,sequence boundary recognition and well-seismic calibration rock formations.The sequence consists of two second-order and six third-order sequences.Sedimentary sequence in the region shows the pattern like the East is thick and the west is thin.SQ2 and SQ3 develop completely only in the eastern area of the depression,while erose and lost in western plateau region;SQ4 and SQ5 only been found in the eastern area of the depression,and in the central and western plateau region are missing erosion and deposition missing;SQ6 is confined to the central and western plateau region,which bottom has lost.North Ordovician strata can be classified into six faces and eleven subfacies like tidal flat,restricted platform,open platform,platform margin slope and shelf.Ordovician sedimentary evolution of the North can be divided into two stages.In the Late Cambrian-Middle Ordovician,with the rising of sea level,the sedimentary faces change from the platform tidal flat ? restricted platform facies? open platform.In Late middle Ordovician stage,Jade North affect by,on the east by the Caledonian?curtain movement.The east evolvevt to the continental shelf platform and the Midwest suffer erosion while uplifting.Mid-late stage in Late Ordovician,sedimentary facies change from the open platform ?slope facies ?continental shelf;In Late Ordovician,the mid-east,in the movement of Caledonian?curtain,the emergence of large scale of Jade North uplift and become denuded zone with the regression.