藏北羌塘盆地菊花山地区晚三叠世古岩溶不整合面的发现及其意义  

Discovery and Significance of Paleokarst Unconformity between the Xiaochaka Formation and the Nadigangri Formation in Juhuashan Region, Qiangtang Basin, Northern Xizang(Tibet)

作　　者：陈文西[1,2] 王剑[1] 汪正江[1] 付修根[1,2] 

机构地区：[1]中国地质调查局成都地质矿产研究所,成都610082 [2]中国地质科学院

出　　处：《地质论评》2007年第5期699-703,729,共6页Geological Review

基　　金：国家油气专项"青藏高原油气资源战略选区调查与评价(科油[2006]02号)"项目;国家自然科学基金资助项目(批准号40472070)的成果。

摘　　要：菊花山地区出露的肖茶卡组—那底岗日组,其接触关系清楚,是北羌塘盆地代表性的剖面。在对该剖面中两者之间的砾岩进行详细的野外观测和分层取样分析的基础上,确定了肖茶卡组顶部与那底岗日组底部之间的砾岩为上、下两套不同成因、不同性质的砾岩组合。下套角砾岩以钙质、铁泥质胶结为特征,是肖茶卡组沉积期后海平面下降,出现广泛暴露、风化溶蚀形成的岩溶角砾岩;上套砾岩以凝灰质胶结为特征,是岩溶角砾未固结之前,发生构造活动产生的火山碎屑、熔岩流携带、搬运松散岩溶角砾再次沉积形成的那底岗日组底砾岩。从而确定了肖茶卡组与那底岗日组为岩溶不整合接触关系。该岩溶不整合面是羌塘盆地构造演化分析的重要证据,也是油气勘探的重要标志层。In the Juhuashan section, the boundary between the Xiaochaka Formation and the Nadigangri Formation is clear, so this section is a typical section in the northern Qiangtang basin, Northern Xizang（Tibet）. We make certain that the gravelstone between the Xiaochaka Formation and the Nadigangri Formation is composed of two parts of different geneses and properties. The lower part is a karst breccia, formed after deposition of the Xiaochaka Formation, is characterized by kalk and fer-muddy cement. The upper part is a basal conglomerate, produced by coulee carrying and transporting the loosening karst rillenstein redeposit. So that, we make further certain that the relationship between the Xiaochaka Formation and the Nadigangri Formation is paleokarst unconformity. The paleokarst unconformity is an important referring evidence for analyses tectonic history and an important mark for exploration of oil-gas in the Qiangtang basin.

关 键 词：岩溶角砾 岩溶不整合 肖茶卡组 那底岗日组 羌塘盆地 西藏 

分 类 号：P534.51[天文地球—古生物学与地层学]