Abstract:

The first member of the Qingshankou Formation recovered by CCSDSKⅠs borehole (China Cretaceous Continental Scientific DrillingSongkeⅠthe south borehole) is 8141 m long and 100% of cores recovery. The age of the member corresponds approximately to the Turonian. The sequence and process of lithologylithofacies and cyclic stratigraphy were revealed by a detailed core description. Six rock types（mudstone, dolostone, marl, limestone, ostracode limestone and volcanic ash）comprise the sedimentary strata. Deposition occurred in a deep lake, including six sedimentary microfacies: dolostone, marl, limestone, deep lake turbidite,  deep lake mudstone  and volcanic ash microfacies. The first member of the Qingshankou Formation represents eightyone meterscale cycles (sixthorder cycle), twentyfive fifthorder cycles, six fourthorder cycles and two thirdorder cycles. The occurrence and detailed description of mudstone, dolostone and volcanic ash are of significance for the study of anoxic events, source rock development and the potential linkage between lakemarine depositional events.

Key words:

first member of Qingshankou Formation; sedimentary facies; sedimentary sequence; cyclic stratigraphy; CCSDSKⅠs; Cretaceous Turonian; Songliao Basin