湖北省栖霞组沉积环境、沉积旋回及层序地层划分

Depositional Environments, Cycles and Sequences of Chihsia Formation in Hubei Province

根据岩石结构、构造及生物碎屑含量等特征,将本区栖霞组分为3类微相:A.生物碎屑灰岩;B.灰泥岩;C.具水平层纹的含炭质泥质细生物屑灰岩(泥灰岩).在剖面上,这3类微相组合成CA、CB或以C微相为主的韵律.不同韵律纵向上有规律的叠置常构成厚约10余米的沉积旋回.根据沉积旋回在垂向上的更替,在本区栖霞组内可识别出4次较大的海平面变化,周期约3My.通过与同期泛大陆北方各大陆上所发育的旋回层的对比,作者认为本区栖霞组内的4次海平面变化属三级海平面变化,对应4个三级层序,为全球冰川性海平面变化的结果,可与同期北美大陆上海平面变化曲线对比.

Based on the texture, structure and content of organic grains in the Chihsia Formation of Hubei Province, microfacies in the formation can be grouped into 3: A. bioclastic limestone (wackestone and packstone); B. mudstone; C. bioclastic limestone or marl with laminae. Vertical alternation of the microfacies comprises rhythms as CA or CB, which in turn constitutes the depositional cycle from CB to C to CB with chert nodules capped by CA. The variation of the depositional cycle vertically enables them to be grouped into 4 major cycles with duration about 3 My. Like mesotherms developed in the Northern Hemispher, 4 major cycles are thought to be resulted from glacio-eustatic sea-level changes in the scale of Vail's third order sea-level change, and represent 4 depositional sequences.