摘要
中国白垩纪大陆科学钻探松科1井北孔连续取四方台组岩心心长209.02m,岩心收获率为97.5%,是迄今获取的最连续完整的沉积记录。文章对此进行了厘米级(分层厚度2~5cm)沉积地质描述。四方台组沉积时期对应中—晚坎潘期。通过对松科1井四方台组岩心的精细描述,揭示其岩性-岩相-旋回的沉积序列及其过程。四方台组共识别出8种岩石类型,为曲流河、浅湖亚相的河床滞留、点砂坝、天然堤、决口扇、决口水道、河漫滩、河漫湖、临滨砂坝、静水泥质沉积和浊流沉积等10种沉积微相。在岩相序列上识别出15种共174个米级旋回(六级旋回)、43个五级旋回、13个四级旋回和2个三级旋回。完整组段厘米级刻画为高精度沉积过程研究提供了可能,四方台组全井段取心对松辽盆地富氧事件、潜在浅层油气储、盖组合等研究具有重要意义。该文的精细描述资料为今后相关的深入研究提供了迄今最精准的基本地质素材。
China Cretaceous Continental Scientific Drilling(CCSD) in the Songliao Basin,called SK1 project,collected 209.02 m of Sifangtai Formation which correspond to middle to late Campanian.The borehole got a highly continuous core section with recovery of 97.5%,that is the most complete and precise sedimentary records up to now in the basin.Thicknesses of the description can be as thin as 2-5 cm for the interbedding sequences.We described in cm-scale the sedimentary sequence,lithology,lithofacies and cyclic stratigraphy at the drilling spot.Eleven litho-types were recognized in the section.Sedimentary facies are predominantly meandering river and lacustrine that can be subdivided into ten microfacies including point bar,natural levee,crevasse splay,crevasse channel,floodplain,flood lake,nearshore bar,mudstone of still water,and turbidite.The whole sequence is composed of 174 meter-scale cycles(sixth-order cycle),43 fifth-order cycles,13 fourth-order cycles and 2 third-order cycles.Centimeter scale description of the section revealed some previously unknown horizons such as special kind of mudstone,favorable sand reservoir of the formation.The new found evidences are very important for us to interprete basin evolution features such as lake oxic and the reservoir-cap rock assemblages in shallow stratigraphy.That is to say,the scientific drilling provides us with powerful insight in to the basin.Researchers who are interested in the basin can do their reasonable analysis about the basin based on the precise original materials of the paper.