二连盆地白音查干凹陷下白垩统都红木组沉积特征及演化

SEDIMENTARY CHARACTERISTICS AND EVOLUTION OF LOWER CRETACEOUS DUHONGMU FORMATION IN BAIYINCHAGAN SAG,ERLIAN BASIN IN INNER MONGOLIA

通过详细的岩芯观察、录测井资料分析,并结合区域地质资料和前人研究成果,对白音查干凹陷下白垩统都红木组的沉积相特征和沉积演化进行了深入研究。结果表明,白音查干凹陷主要发育扇三角洲相、辫状河三角洲相、浊积扇相和湖泊相4种沉积相类型。其中,扇三角洲和浊积扇在陡峭的北坡发育,辫状河三角洲在宽缓的南坡沉积,湖泊相分布在扇三角洲和辫状河三角洲的侧翼及凹陷的中心。都红木组沉积时期白音查干凹陷处于强裂陷向坳陷转化阶段。根据残留地层分布特征,其沉积演化可分为早、中、晚3个时期,从早期至晚期,扇三角洲和辫状河三角洲的面积不断缩小,分别后退了约3km和4-11km,湖泊沉积成为主体。

Sedimentary facies characteristics and evolution of the Duhongmu Formation of Lower Cretaceous in Baiyinchagan Sag were thoroughly studied using core observation data,well logging data,regional geologic data,and previously published data. The study shows that the sedimentary facies are dominated by the fan delta,braided-river delta,turbidite fan and lacustrine facies. Fan delta and turbidite fan were deposited at the steep northern slope,and braided-river delta deposits occur at the southern gentle slope. In addition,at the border of fan delta,braided-river delta as well as the centre of sag developed lacustrine facies mainly occurs in the center of the sag. The Baiyinchagan Sag transformed evolved from a strongly faulted basin to a subsiding depression sunken during the time interval when the deposition of Duhongmu Formation was deposited. Sedimentary evolution of the Duhongmu Formation can be divided into early,middle and late stages. From early to late stage,the area distribution of fan delta facies and braided-river delta facies gradually reduced,and backward about retreating by 3 km and 4-11 km,respectively. At the same time,the distribution of lacustrine facies expanded and became the main sedimentary facies.