Abstract:

China Cretaceous Continental Scientific Drilling (CCSD) in the Songliao Basin, called SK1 project, collected 55894 m of Mingshui Formation which corresponded to the late Campanian to Danian. The borehole got a highly continuous core section with recovery of 93.69%，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 in centimeterscale the sedimentary sequence, lithology, lithofacies and cyclic stratigraphy at the drilling spot. Fifteen lithotypes were recognized in the section. Sedimentary facies are predominantly river and lacustrine that can be subdivided into fifteen microfacies including point bar, natural levee, crevasse splay, crevasse channel, flood plain, flood lake, mudstone of still water, nearshore bar，tempestite，sandy beach，mudy beach，turbidite and gravity flow channel microfacies. The whole sequence is composed of 361 meterscale cycles (sixthorder cycle), 109 fifthorder cycles, 29 fourthorder cycles and 3 thirdorder cycles. Centimeter scale depiction of the section revealed some previously unknown horizons, which is  very important for us to interpret basin evolution features such as lake oxic events, K/Pg boundary，tectonism in late sag basin stage and the sourcereservoircap rock assemblages in shallow stratigraphy. 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 in the paper.

Key words: Songliao Basin, SK1, Mingshui Formation, sedimentary facies, sedimentary sequence, cyclostratigraphy