摘要
豫西渑池地区寒武系第三统馒头组二段主要由紫红色、褐黄色页岩夹叠层石灰岩、核形石灰岩和鲕粒灰岩组成,其下部灰岩中富含核形石,形态和纹层结构多不规则,可见弯曲、不分枝的葛万菌(Girvanella)管状体呈密集而不规则的网状缠绕于核心和暗色纹层中,在亮纹层中则少些。含核形石地层呈薄层或透镜状夹于鲕粒灰岩之间或被潮上带泥岩覆盖,形成于低能的滨岸鲕粒滩滩间或滩后洼地。从核形石的特征可以看出,后生动物的匮乏或衰退是渑池地区馒头组二段核形石产生的决定性因素,不同的水动力条件造就了核形石形态类型的多样化,持续动荡的高能条件和大量泥质(陆源物质)供应直接导致了核形石消亡。
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.
出处
《高校地质学报》
CAS
CSCD
北大核心
2013年第4期634-641,共8页
Geological Journal of China Universities
基金
国家自然科学基金项目(41072003)
河南省基础与前沿项目(112300413213)
高校博士点基金博导类联合课题(20114116110001)联合资助
关键词
渑池
核形石
控制因素
馒头组二段
寒武系第三统
Mianchi
oncoids
controlling factors
the Second Member of Mantou Formation
the Third Series of Cambrian
