青海省宗马海湖地区始新—中新统干柴沟组沉积相探析

Preliminary study on Sedimentary Facies of Eocene-Miocene Ganchaigou Formation in Zongmahaihu of Qaidam Basin in Qinghai Province

宗马海湖地区位于柴达木盆地的北缘,有着良好的油气、钾盐勘探前景。该文在分析柴达木盆地北缘宗马海湖地区区域地质背景的基础上,对始新-中新统干柴沟组的岩石学特征、地层特征、沉积构造特征及沉积相等进行了较为深入的研究。干柴沟组沉积相以滨湖亚相、浅湖亚相及扇三角洲相为主,滨-浅亚湖沉积发育最为广泛。扇三角洲相具牵引流、重力流沉积特征,中、粗粒碎屑岩为主;滨湖亚相具较高流态的水动力条件,以砂和粉砂为主,砂泥间互层频繁;浅湖亚相以泥质沉积为主,显示低能的浅水静态沉积作用。文中总结了研究区干柴沟组沉积期沉积相演化特征,建立了干柴沟沉积相平面展布图;干柴沟组沉积相的形成与季节性变化息息相关,湖水上涨、后退导致北部山区扇三角洲较发育,而南部区域始终位于滨、浅湖环境中。

Zongmahaihu area is located in the northwest margin ol Qaidam basin. It is an important part ol the Qaid-am Basin in Qinghai Province and has a good exploration potential ol oil gas and potassium. On the basis ol analy-zing regional geological background in Zongmahaihu area,through study on petrologic, stratigraphic, sedimentary and sedimentary structural leatures,Eocene Miocene Ganchaigou Formation is studied in depth. In the study area,Eocene Miocene Ganchaigou Formation has been divided into three important types ol sedimentary lacies, inclu-ding shore lake lacies,shallow shore lake,lan delta lacies. Among them,the lakeshore lacies,shallow lake subla-cies area is the most widely,Fan delta development in local area. Fan delta lacies have two kinds ol characteristics at the same time,traction current and gravity llow deposits. In the composition ol the rocks,the content ol conglom-eratic sandstone and coarse sandstone is most,then with a thin layer ol line sandstone, mudstone. The hydrodynam-ic conditions ol Shore lake lacies are characterized by high fluidity,the energy ol water medium is higher under the ellect ol lake wave. Sediments are dominated by sand and silt. The characteristics ol mudstone and sandstone inter-bed are obvious,and the thickness ol single sand layer is more stable. Shore lake lacies are mainly composed olshallow water sediments with small energy and stable sediments,sediments are mainly mudstone. During the deposi-tion period ol Ganchaigou Formation,Regional climate or seasonal changes lead to lake water up or back,but themagnitude is limited. The northern mountain,lan delta lacies is relatively developed,While the southern region olstudy area is always located in the lakeside and shallow lake environment.