西秦岭文县地区关家沟组海底扇沉积体系  

SUBMARINE FAN DEPOSITIONAL SYSTEMS OF THE GUANJIAGOU FORMATION IN WENXIAN, WEST QINLING

作　　者：苏春乾[1] 刘继庆[1] 王瑶培[1] 

机构地区：[1]长安大学地球科学与国土资源学院,陕西西安710054

出　　处：《长安大学学报（地球科学版）》2003年第4期21-26,31,共7页

基　　金：国土资源部区域地质调查项目(190910200105);国土资源部成矿作用及其动力学开放研究实验室资助项目

摘　　要：　对西秦岭南部文县地区关家沟组的成因,学者之间的认识存在较大分歧,长期以来被看作是可与南沱组对比的冰碛层。关家沟组形成于新元古代末期(晚震旦世),沿扬子板块西北边缘分布。根据地层剖面和扇地质体的平面填图研究表明,关家沟组存在两种沉积体系———海底扇沉积体系和盆地沉积体系;海底扇沉积体系中发育大量的各种类型的粒序层理及鲍玛层序;扇体的剖面结构相似于Walk er(1979)提出的海底扇反旋回沉积序列,层理类型与Winn和Dott(1979)提出的海底扇的层理类型类似;扇体的平面结构(填图追索圈定)清楚地显示了海底扇砂砾岩与盆地相页岩、硅质岩之间的穿插相变关系。其剖面结构可划分出4个级别的不对称它旋回性韵律,显示出扇体向盆地推进和相对海平面的降低。研究表明关家沟组砂砾岩为海底扇沉积体系,而非冰碛层。Origin type of the Guanjiagou formation in Wenxian, the West Qinling is still major divergence of views between scholars. For a long-term past, it is treated as moraine facies(comparison with Nantuo formations). The Guanjiagou formation　had been formed during Neo-Proterozoic Era(Z2), and is distributed along the northwest side of the Yangzi plate. On the based of research of stratigraphic section and surface survey of fan body, there are two types of the depositional systems (the deep-water submarine fan and basin facie depositional systems) in the Guanjiagou formation; A large number of the multi-typical graded beddings and Bouma sequence are developed in the deep-water submarine fan depositional system; The section organization of fan body is similar to the reverse cycle depositional order of Walker's (1979) submarine fan, bedding types are analogous to Winn and Dott's (1979) types of submarine fan. The plane organization of fan body clearly displays the inserting facies change relations between submarine fan sand-conglomerate and shale, silicolites of basin-facies. The section organization of the Guanjiagou formation may be divided into four grades asymmetric allo-cyclical rhythm. It displays that the fan body moved toward basin and the relative sea level decreased. It demonstrates that the Guanjiagou formation is the deep-water submarine fan depositional systems, but not moraine facies.

关 键 词：海底扇沉积体系 基本层序 扇地质体 地层剖面 西秦岭 

分 类 号：P512.2[天文地球—地质学]