Abstract:

 China Cretaceous Continental Scientific Drilling (CCSD) in the Songliao Basin, called SK1 project, collected 29553 m of the lower members 1&2 of Nenjiang Formation which correspond to the late Santonian to early Campanian. The borehole got a highly continuous core section with recovery of 9745%，that is the most complete and precise sedimentary records up to now in the basin. Thicknesses of the description can be as thin as 25 cm for the interbedding sequences. We described  the sedimentary sequence, lithology, lithofacies and cyclic stratigraphy at the drilling spot in cmscale. Twelve lithotypes were recognized in the section. Sedimentary facies are predominantly lacustrine that can be subdivided into seven microfacies including dolomite, marl, argillaceous limestone, oil shale, turbidite, deep lake mudstone and volcanic ash microfacies. The whole sequence is composed of 213 meterscale cycles (sixthorder cycle), 54 fifthorder cycles, 12 fourthorder cycles and 2 thirdorder cycles. Centimeterscale depiction of the section revealed some previously unknown horizons such as special kind of mudstone, dolomite and volcanic ash of the formation. The new found evidences are very important for us to interpret basin evolution features such as lake anoxic, source rock development and the potential linkage between lake and adjacent sea. That is to say, the scientific drilling provides us with powerful insight into the basin. Researchers who are interested in the basin can do their reasonable analysis of the basin  on the basis of the precise original materials of the paper.

Key words: Songliao Basin, SK1, the first and second members of Nenjiang Formation, sedimentary facies, sedimentary sequence, cyclostratigraphy