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云南曲靖地区是我国非海相下泥盆统的标准剖面所在地。本次工作逐层实测了徐家冲组剖面,从剖面的沉积旋回入手,研究分析了沉积旋回的特征、岩石组合特征,根据植物化石和动物化石讨论了该剖面徐家冲组的沉积环境和地质年代。徐家冲组厚841.84 m,分为93个沉积旋回。其沉积模式是由砂岩、粉砂岩、泥岩和粉砂岩构成四元结构的沉积旋回,每个旋回都是从砂岩开始,以粉砂岩或泥岩结束。徐家冲组的沉积模式与典型辫状河、曲流河及三角洲沉积体系都有明显的区别。沉积环境应该是三角洲平原靠陆部分的河流环境。亚环境有河床、漫滩、天然堤、泛滥平原、废弃河道及岸后湖泊。根据植物化石及双壳类、鱼类化石,徐家冲组中下部地质时代为(晚)布拉格期,上部为早埃姆斯期。同时讨论建立了徐家冲植物群及组合带。
The Qujing area in Yunnan Province is the location of the standard profile of the non-marine Lower Devonian in China. This work measured the profile of Xujiachu Formation layer by layer. Starting from the sedimentary cycle of the section, the characteristics of sedimentary cycles and the characteristics of rock assemblages were studied. The sedimentary environment and geochronology of Xujiachuang Formation were discussed based on plant fossils and animal fossils. The Xujiachu Formation is 841.84 m thick, divided into 93 sedimentary cycles. The sedimentary model is a quaternary sedimentary cycle formed by sandstone, siltstone, mudstone and siltstone. Each cycle begins with sandstone and ends with siltstone or mudstone. Sedimentary model of Xujiachu Formation is obviously different from that of typical braided river, meandering river and delta sedimentary system. The sedimentary environment should be the river environment where the Delta plain lands. Sub-environment riverbed, floodplain, natural dykes, flood plains, abandoned river courses and shore lakes. According to plant fossils and bivalves, fish fossils, the Xujiachu Formation in the middle and lower geological period (late) Prague period, the upper part of the early Ames period. Meanwhile, Xujiachong flora and its combination belt were discussed.