• 责任者：Qi Yong’an (Key Laboratory of Biogenic Traces and Sedimentary Minerals of Henan Province ; School of Resources and Environment ; Henan Polytechnic University ; Jiaozuo 454000 ; China) ; Dai Mingyue
• 刊名：Geological Journal of China Universities
• 出版年：2013
• 卷期：19(4)
• 关键词：核形石 ; oncolites ; 河南 ; Henan Province
• 页码：p.634-641
• 图表：4 illus., 21 refs.
• 分类号：0803
• issnNo：ISSN1006-7493
• isbnNo：CN32-1440/P

     The Second Member of Mantou Formation （the Third Series, Cambrian） crops out in Mianchi Area of western Henan and is characterized by purple and isabelline mudstones interbedded with stromatolite, oncoidal and oolitic limestones. Abundant oncoids occur in the lower part of the Member. They exhibit variations of shapes, irregular cortex structures and clearly winding Girvanella filamentous structures. These filaments are mainly found in the core and dark-colored laminae, and are less found in light-colored laminae. They display as flexuous, unsegmented and unbranched tubular objects and constitute a dense and dark network. The settings containing oncoids occur as thin-bedded or lenses between oolitic limestones or are underlain by upper supratidal mudstones. They are preserved in low-energy coastal oolitic inter-shoal or back-shoal facies. The genetic analysis on oncoids shows that： barren of metazoan plays a determining role for the occurence of oncoids in the Second Member of Mantou Formation, Mianchi area; the diversified shapes of oncoids are associated to different water energy; the high-energy condition of sustained agitation and influx of terrigenous clays are the direct controlling factors for the ultimate demise of oncoids.