松潘地区白龙江隆起泥盆纪至三叠纪碳酸盐碎屑流沉积及其古地理意义

Carbonate debris flow deposition from Devonian to Triassic in Bailongjiang uplift,Songpan area and its palaeogeographical implications

白龙江隆起地区可见泥盆纪至中三叠世的碳酸盐碎屑流,其中泥盆纪至早三叠世的碳酸盐碎屑流沉积主要见于白龙江隆起北翼,中三叠世的碳酸盐碎屑流则见于白龙江隆起南北两翼和西缘。这些碳酸盐碎屑流沉积有两种类型:一种为仅含深水砾屑的碎屑流沉积,另一种为深水和浅水砾屑兼有的碎屑流沉积。通过对这些碎屑流沉积进行详细的野外和室内研究,分析其沉积特征,认为这些碳酸盐碎屑流形成于碳酸盐台地斜坡环境。结合前人的研究成果分析认为,白龙江地区北侧自泥盆纪开始,存在一个大致东西走向,向北倾斜的碳酸盐斜坡,斜坡向南则为松潘-甘孜地块的主体部分,从侧面佐证了松潘-甘孜地块的存在。至三叠纪安尼晚期,由于松潘地块主体部分沉陷,形成自东向西延伸的白龙江半岛,中三叠世白龙江隆起周缘碳酸盐碎屑流沉积的环状分布则指示出白龙江半岛的空间展布特征。

There are a lot of carbonate debris flows in Bailongjiang uplift from Devonian to Middle Triassic.The carbonate debris flow deposition from Devonian to Early Triassic are mainly found in the north wing of Bailongjiang uplift,and carbonate debris flow deposition in Middle Triassic are mainly located in the both wings and the western edge of this area.The carbonate deris flow depositions can be divided into two types,including the deposition containing only deep water gravels and the deposition containing both shallow and deep water gravels.Through detailed investigation in field and laboratory of these carbonate debris flow depositions,the authors analyse their sedimentary characteristics and consider that these carbonate flows formed in carbonate slope environment.Combining with the previous research,the authors draw a conclusion that there was a carbonate slope with east-west striking and north trending in the north edge of Bailongjiang uplift from Devonian,and the main part of Songpan—Ganzi block southward from Bailongjiang uplift,which evidenced the existence of Songpan—Ganzi block.Due to the subsidence of the main part of Songpan block,Bailongjiang peninsula formed with east-west striking in late Anisian of Triassic.The ring distribution of the carbonate debris flow depostion enclosing Bailongjiang uplift in Middle Triassic showed the spatial distribution characteristics of Bailongjiang peninsula.