牛庄洼陷王58地区沙四段上亚段纯上3砂组浊积岩沉积特征及形成机制

Sedimentary characteristics and formation mechanism of turbidite,the upper ShaⅣmember,Wang58 rgion of Niuzhuang sag

以断陷湖盆层序地层划分为基础,采用岩心观察、沉积体系分析等方法,重点研究了牛庄洼陷王58地区沙四段上亚段纯上3砂组浊积岩的沉积特征和展布形态,并应用湖平面变化结合构造演化分析了浊积扇的发育特点和成因机制。研究结果表明,牛庄洼陷王58地区沙四段上亚段纯上3砂组发育单一坡折远岸浊积扇,沉积特征表明主要发育辫状水道以及水道间微相;同时运用具有相指示作用的特殊标志物确定了自洼陷东南部的物源在近源处沉积扇三角洲相,在洼陷区沉积浊积扇相;通过对沙四段上亚段纯上4个砂组砂体发育的对比,提出湖平面变化结合构造形态以及物源共同控制了浊积扇的发育和展布特征的观点。物源充分,坡度较大,洼陷较局限是浊积扇发育的有利条件。

Based on the division of sequence stratigraphy in rift-subsidence basin,as well as the core observation and analysis of the sedimentary system,we focus on the sedimentary characteristics and distribution patterns of turbidite in the upper ShaⅣmember of Wang58 region in Niuzhuang sag,and analyze the development and formation mechanism of the turbidite fan by means of lake level change and tectonic evolution.It is concluded that the far-shore turbidite fan is developed on the individual slopebreak of the third member upper ShaⅣmember Wang58 region in Niuzhuang sag,and it is developed between the braided channel and channel facies;At the same time,the special facies indicator indicates that the source is from the southeast,and adjacently deposited as the fan delta,and turbidite fan in the sag center.Moreover,based on the stratigraphic correlation on the four sand groups in the study area,it is concluded that the original source system is the fan delta in southeastern of Niuzhuang sag,and it is controlled both by the lake level change and the tectonic evolution and the original source system,therefore,the slope and the limited sag center are the favorable conditions for the development of turbidite fan.