内蒙葫鲁斯太上石炭统太原组辫状河三角洲沉积

Braided-river delta of the Taiyuan Formation of the Upper Carboniferous in the Hulusitai area of Inner Mongolia

内蒙葫鲁斯太地区上石炭统太原组中发现一套由辫状河进积到海盆中而形成的辫状河三角洲。由辫状河三角洲前缘及前三角洲 2个亚相组成 ,辫状河三角洲特征显著 ,明显有别于其它类型的三角洲。辫状河三角洲的主体是由含砾砂岩及中、粗粒砂岩组成的辫状河道沉积及水下分流河道沉积 ,它们由许多下粗上细的砂岩透镜体在垂向上相互叠置而成 ,单一透镜体最大厚度在 0 .5 - 2 .5m不等。三角洲中交错层理丰富 。

Braided river delta that braided river systems prograde into an ocean basin is first found in the Upper Carboniferous in the Hulusitai area of Inner Mongolia. Their characters are distinct and significantly different from the other types of deltas. Two sedimentary subfacies: braided river delta front subfacies and prodelta subfacies are recognised. The deposits of braided river deltas are mainly composed of pebbled sandstone and medium to coarse grained sandstones. The bars of the subaqueous distributary channels are the main bodies of deltas. A single channel bar has a thickness of 0.5m 2.5m. Many, finger upward lenticular channel sand bodies pile vertically up each other. Cross stratifications are abundant in the braided river deltas, but lateral accretion cross beddings resulting from lateral accretion of channel sand bodies are the most principal sedimentary structures and one of the most distinct character of braided river deltas.