Sedimentary microtopography in sequence stratigraphic framework of Upper Ordovician and its control over penecontemporaneous karstification, No. I slope break, Tazhong, Tarim block

In order to reveal the relationship between the penecontemporaneous karstification and sedimentary microtopography in sequence stratigraphy, the sequence stratigraphic framework of Lianglitage formation in Upper Ordovician is studied according to the well drilling, logging, geophysical data, detailed observations of core and the paleontology. The Lianglitage formation belongs to the sequence IV of Ordovician. The second member of Lianglitage formation is prograde sedimentation in highstand systems tract, and is favorable for developing reef flat. The development scale and thickness of reef flat are controlled by the variation of secondary sea level. The types and characteristics of karst in the highstand systems tract show that the late highstand systems tract is dissolved and cemented by the meteoric fresh water and mixed water. Penecontemporaneous karstification is developed at the top of parasequence and high place of geomorphology. Atmospheric diagenetic lens is formed. The developing regulations and controlling factors of penecontemporaneous karstification can provide new clues to the prediction and exploration of favorable reservoir in this area.