南天山野云沟石炭系海底扇沉积新发现

DISCOVERY OF SUBMARINE FAN IN THE CARBONIFEROUS IN THE YEYUNGOU AREA OF SOUTH TIANSHAN

南天山野云沟石炭系上部碎屑岩中存在典型的鲍玛序列浊积构造以及滑塌构造、包卷层理等重力流沉积构造。由地层剖面分析和岩相特征及粒度统计分析的C-M图解可知,南天山野云沟石炭系上部的碎屑岩形成于海底扇环境,可划分出杂乱砾岩相(A_1)、无碟状构造块状砂岩相(B_2)、近基浊积岩相(C)、远基浊积岩相(D)、滑塌角砾岩相(F)、页岩夹硅质岩相(G)等岩相类型,它们组合构成了Walker海底扇模式中的扇根、扇中、扇端。因而,首次证实南天山野云沟石炭系中存在深水海底扇沉积。古流向资料计算结果表明,其物源来自南侧的古塔里木陆块,古坡向倾向北。碎屑物常量化学成分投点表明,其形成时构造背景属被动大陆边缘。

Bouma sequences and other sedimentary structures formed by sedimentary gravity flow, such as slump-folded layers and flute casts, are really well developed in upper parts of the Carboniferous in the Yeyungou area of South Tianshan in China. Based on analyses of sections and lithofacies of the upper parts of Carboniferous, accompanied by C - M diagram from the statistics of sand grains in the turbidites, the authors point out that the upper parts of the Carboniferous in the Yeyungou area of South Tianshan in China were formed in submarine fan. Lithofacies such as disorganized gravels ( A_1 ), massive sandstones without dish structures (B_2 ), proximal turbidites (C), distal turbidites (D), slump-folded layers (F), and shales interval siliceous rocks (G) have been recognized in the strata, which are associated with construction of inner fan, mid fan and outer fan according to Walker models of submarine fan. It is verified that there is a sedimentary environment for deep marine fan in the Carboniferous in the Yeyungou area of South Tianshan in China. Paleo-current orientation shows that the sediments came from the south side, paleo-conti-nent of Tarim. The data of chemical composition of sediments indicate that the tectonic background of the turbidites is passive continental margin environment.