渤海湾盆地南堡凹陷古近系重力流沉积特征及模式

Sedimentary Characteristics and Model of Paleogene Gravity Flow in Nanpu Sag,Bohai Bay Basin

利用岩芯微观描述、宏观观察,三维地震资料解译处理等技术并参考前人研究成果对南堡凹陷古近系重力流沉积特征、模式及影响因素进行了研究。结果表明凹陷主要发育滑塌岩、砂质碎屑流沉积、浊积岩三种重力流沉积物,其中砂质碎屑流沉积发育程度最高,单井钻遇累计厚度达220 m、单层厚可达30 m,粒度概率累积曲线大都呈现两段式,C-M图与QR段平行,显示沉积的非牵引流成因;浊积岩具有多期发育的特征,单层厚多小于1 m,具有正粒序层理,发育不完整鲍马序列Tc段常见Td段少见,常见于砂质碎屑流沉积外围及上部;滑塌岩颗粒粒级较细,揉皱构造和包卷层理极为发育,在4号构造发育程度较高。沙垒田、马头营等凸起,古近系活跃的火山、断层活动及地震,东营组及沙河街组发育期深水环境、坡折带的存在为重力流沉积的形成提供了条件。综合各种因素为研究区建立了扇三角洲—短陡坡型(1号、4号构造)及辫状河三角洲—长缓坡型(2号、3号构造)重力流沉积模式并对其沉积规律进行了分析。

Based on the microscopic description of core,macroscopic observation,3 D seismic data interpretation and previous research results,this paper studied the sedimentary characteristics,patterns and influencing factors of the gravity flow in Paleogene of Nanpu sag. Research results show that： Slump rock,Sandy debris flow,Turbidity flow is the mainly types of gravity flow deposit in Nanpu sag. Among them,the development degree of sandy debris flow is the highest. Cumulative thickness of single well drilling is 220 m,single layer thickness is up to 30 m. Cumulative grainsize distribution curve largely present two stages,C-M diagram is parallel to the QR segment,this Shows the origin of the deposited non-traction flow; Turbidity flow develops positive grading. Single layer thickness is less than 1 m but it has characteristic of multiple stage development. Incomplete Bao Ma sequence can be seen in it and Tc Period is easier to see but Td Period is rare. Turbidity flow is commonly found in the outer and upper parts of sandy debris flow deposit; the size of slump rock particle is smaller,crumpled structure and convolute bedding are extremely developed,the development degree of slump rock is higher in structure 4. Shaleitian,Matouying and other uplifts,active volcano,fault activity and earthquake in Paleogene,deep water environment of Dongying Formation and Shahejie Formation,as well as slope break zone provide the conditions for gravity flow deposition. Finally,considering the various factors we establish gravity flow sedimentation model of fan delta-short steep slope type（structure 1,4） and Braided River Deltalong ramp type（structure 2,3） for Nanpu sag,and then this paper analyzes different deposition rules of them.