摘要:
日喀则群砂泥质复理石的浊积层序非常发育,包括富泥的粘性高密度浊流、砂质高密度浊流、低密度浊流和Pickering及Hiscott (1986)的限制性泥质高密度浊流的沉积层序。其中,低密度浊流沉积层序的组合与鲍马(Bouma)层序很相似,两者的区别在于沉积的粒度、粒级分布范围、层序厚度和相组合等特征的不同。沉积相序、古流向和物源分析表明,日喀则群复理石盆地的南侧主要发育单向物源的海底扇体系,而盆地北侧以发育双向物源和多种沉积流体的复合沉积为特征。值得指出的是,特殊的浊积类型——限制性泥质高密度浊流沉积的发现为论证日喀则群复理石盆地属残留盆地又提供了一条有力的依据。
Abstract:
The turbidite sequences are recognized in the sandy and muddy flysch of the Xigaze Group in Xizang, including the sedimentary sequences resulted from the mud-rich cohesive high-density turbidity current, sandy high-density turbidity current, low-density turbidity current and "contained" muddy high-density turbidity current proposed by Pickering and Hiseott (1986), of which the sedimentary sequences resulted from the low-density turbidity current are closely similar to the Bouma sequences. But there are significant differences between them in grain size, grain-size distribution, sequence thickness and facies associations.
The analysis of sedimentary facies sequences, palaeocurrent direction and provenance indicates that the submarine fan systems of monodireetional source are well developed on the southern flank of the Xigaze flyseh basin, while the composite deposits derived from bidirectional sources and resuited frommultiple flows are recognized on the northern flank of the flysch basin. Furthermore, the discovery of a special turbidite type-the "contained" muddy high-density turbidity current deposits attests to the conclusion that the sedimentary basin of the Xigaze flysch is a residual one.
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