Responses of karst on sequence interfaces—a case study of Ordovician in Tarim Basin, NW China

Sequence interfaces of various levels have critical controlling effect on the development and distribution of carbonate karst. Under suitable climate and time conditions, karstification can occur below various-level sequence interfaces in carbonate rock. Late karst in highstand system tract can occur below the sequence interfaces in the 4th–6th levels, karst in lowstand system tract can occur below the sequence interface in the 3rd level, and weathering crust karst can occur below the sequence interfaces in the 1st–2nd levels. Each higher-level karst can also be superimposed with one or more previous lower-level karsts. In Tarim Basin, the biggest interior basin of China, the Ordovician system is one of the important exploration target series in current oil and gas exploration, and the karst reservoir is the major reservoir in the Ordovician system. In this paper, in order to reveal the controlling mechanism of the sequence interfaces on karstification in Ordovician carbonate rock, based on study on tectonic setting, through comprehensive studies on drilling and electrofacies, seismic facies interpretation, core description, thin slice analysis, etc., the sequence stratigraphy framework of the Ordovician in the Tarim Basin has been established, and the karstification between the sequence interfaces in the 1st–4th levels of the Ordovician in the Tarim Basin was identified. © 2021, Saudi Society for Geosciences.