藏北安多—巴青地区侏罗纪含礁层系岩相及沉积环境

FACIES AND ENVIRONMENTS OF JURASSIC REEF-BEARING STRATA IN ANDUO—BAQING AREA, NORTHERN XIZANG(TIBET)

根据岩性及其组合特征,本文将西藏北部安多—巴青地区侏罗纪含礁地层划分为流水成因的颗粒岩岩相、流水成因的碎屑岩岩相、复成因的泥晶—泥质灰岩岩相、生物及生物化学成因的障积岩岩相、生物及生物化学成因的粘结—障积岩岩相和生物及生物化学成因的骨架岩岩相等6大类型,计16种岩相。它们构成了潮坪相组合、台地浅滩相组合、开阔台地相组合和台地生物礁相组合共4种岩相组合,并由下而上有规律地形成2种岩相序列,即陆源碎屑与碳酸盐混合台地相序列和碳酸盐台地相序列。

Based on the characteristics of lithologies and rock associations, the Jurassic reef-bearing strata in Anduo-Baqing area, northern Xizang （Tibet）, could be classified into 6 groups of lithofacies： water current genetic grainstone, water current genetic clastic rock, polygenetic micritic limestone and marl, biogenetic and biochemical genetic baffling rock, biogenetic and biochemical genetic cemented-baffling rock, as well as biogenetic and biochemical genetic framestone. These lithofacies made up four kinds of lithofacies associations： tide plat, open platform, platform shoal and platform reef ones. The four lithofacies associations constituted two depositionary successions in ascending order, namely, the succession of mixed carbonateterrigenous platform lithofacies and succession of carbonate rock platform lithofacies. Both of them indicated a relatively stable tectonic setting of shallow marine platform, different from the lithofacies associations and sedimentation of back-arc basin in Early Cretaceous.