海拉尔盆地呼和湖凹陷白垩系层序地层特征及沉积体系分布

CRETACEOUS SEQUENCE STRATIGRAPHY AND SEDIMENTARY SYSTEM IN HUHEHU DEPRESSION,HAILAER BASIN

以层序地层学理论为指导,通过对全凹陷范围内的地震、钻井、测井、岩芯以及古生物等资料的综合研究,建立了呼和湖凹陷白垩系层序地层格架。呼和湖凹陷白垩系划分为3个一级层序(TSq1—TSq3)、5个二级层序(Ⅰ—Ⅴ)、8个三级层序(Sq1—Sq8),并在层序格架内进行沉积相划分和沉积体系研究,确定该区主要发育冲积扇、扇三角洲、辫状河三角洲、湖底扇和湖泊沉积等沉积体系。冲积扇沉积体系主要分布在早期Sq1层序中;扇三角洲沉积体系主要分布在各层序的陡坡带,且在Sq2层序中尤为发育;辫状河三角洲沉积体系主要分布在Sq3、Sq4、Sq5层序的缓坡带;湖底扇沉积体系主要发育在Sq2和Sq4层序的洼陷带;沉积体系在平面与纵向上的演化受古构造与古地貌的控制,呼和湖凹陷南部沉积砂体为较有利的勘探区域。

A sequence stratigraphic framework of the Cretaceous System in the Huhehu Depression is established in this paper on the basis of comprehensive integration of seismic data,drill cores and well log data.The Cretaceous System in the Huhehu Depression is divided in to three first-order sequences（TSq1-TSq3）,five second-order sequences（Ⅰ-Ⅴ）,and eight third-order sequences（Sq1-Sq8）.Sedimentary facies such as alluvial fan,fan delta,braided river delta,sublacustrine fan,and lake deposition are recognized.Alluvial fan sedimentary system mainly occurs in Sq1 sequence.Fan delta sedimentary system mainly occurs in the steep slope zone of each sequence,and especially in Sq2 sequence.Braided river delta sedimentary system is found in the gentle slope belt of Sq3,Sq4,and Sq5 sequences.Sublacustrine fan sedimentary system occurs in the depression belt of Sq2 and Sq4 sequences.Sedimentary system evolution was controlled by paleostructures and palaeogeomorphology.Cretaceous sand bodies in the southern Huhehu Depression are important in the exploration of this area.