鄂东黄石地区下三叠统大冶组风暴沉积

鄂东黄石地区下三叠统大冶组灰岩中发育了典型的风暴沉积，风暴岩由砾屑灰岩、颗粒灰岩和泥灰岩组成，其中风暴沉积构造包括丘状交错层理、递变层理、砾屑的撕裂构造及水平层理等，不同层位具有不同的风暴沉积构造类型和组合特征。根据风暴沉积的岩石特征、构造类型、规模、组合特点，并结合沉积背景分析，风暴沉积序列可进一步分为深水远源型、过渡型和浅水近源型。大冶组一段风暴沉积具有深水远源特点，沉积环境为水体较深的外陆棚； 大冶组二段风暴沉积具有过渡型特点，沉积环境为向上变浅的内陆棚； 大冶组三、四段风暴沉积具有浅水近源特点，沉积环境为浅水陆棚至滨岸。大冶组沉积序列具有向上变浅的特点，沉积环境由深水陆棚逐渐向滨岸转变。风暴沉积的识别对重建鄂东黄石地区早三叠世古地理具有重要意义。

Storm deposits of the Daye Formation of Lower Triassic in Huangshi area of eastern Hubei Province

Typical storm deposits are developed in the limestones of the Daye Formation of Lower Tri- assic in Huangshi area,eastern Hubei Province. The tempestites include gravel-sized intraclastic lime- stone,grain limestone and marl. The sedimentary structures of storm deposits include hummocky cross- bedding,graded bedding,tearing structures and horizontal bedding.Besides,the types and assemblage features of storm deposit sedimentary structures are different at different stratigraphic intervals. Based on the lithologic characteristics,types of sedimentary structures,sizes and assemblage features of storm depos- its,combined with analysis of sedimentary background,the sedimentary succession of the Daye Formation storm deposits can be subdivided into 3 types:deep-water distal sequence,transitional sequence,and shallow-water proximal sequence.The Member 1 of Daye Formation is characterized by a deep-water distal sequence,which was mainly deposited in the deep water outer shelf.The Member 2 is dominated by a transitional sequence,which was deposited in the inner shelf.The Members 3 and 4 are characterized by a shallow-water proximal sequence,which was mainly deposited in the shallow water shelf to littoral environ- ment.The Daye Formation comprises an upward shoaling succession,and its sedimentary environment changes from the outer shelf to the littoral facies.The recognition of the storm deposits in Daye Formation is important for reconstructing the Early Triassic palaeogeography in Huangshi area of eastern Hubei Prov- ince.