鄂东南地区早三叠世风暴沉积序列及其环境意义

Sedimentary Successions of the Early Triassic Tempestite in Southeastern Hubei Province and Their Environment Significance

鄂东南地区下三叠统以海相碳酸盐岩为主,发育典型的风暴成因的竹叶状砾屑灰岩。风暴沉积构造包括风暴侵蚀构造、风暴撕裂构造、风暴浪构造、风暴涡流构造及风暴期后快速沉积构造和放射状构造等。风暴沉积主要包括7种岩相类型:A为具块状层理的竹叶状砾屑灰岩;B为具递变层理的砾屑灰岩;C为具丘状、洼状交错层理和平行层理的砂屑灰岩;D为具平行层理的砂屑灰岩;E为具波痕交错层理的砂屑灰岩;F为具水平层理的粉屑灰岩;G为具块状或水平层理的泥状灰岩。它们组成4种典型的风暴沉积序列:风暴潮序列(序列1)、潮下带风暴流序列(序列2)、内陆棚风暴流序列(序列3)和外陆棚风暴浊流序列(序列4)。鄂东南地区广泛发育的风暴沉积,说明三叠纪时期该地区处于低纬度带的潮坪—陆棚浅水沉积环境。

The Lower Triassic in the Huangshi area, southeastern Hubei Province, is mainly marked by carbonate rocks. In this set of strata ＂wormkalk＂calclrudite belonging to storm deposit are developed. The storm sedimentary structures include erosional structures, tear-pull structures, storm-wave structures, storm eddy structure and radial fabric, quickly depositional structure after storm. The storm deposits of the Early Triassic can be grouped into 7 types of lithofacies. （A）＂wormkalk＂ calclrudite with massive bedding, （B）＂wormkalk＂ calclrudite with graded bedding, （C）calcarenite with hummocky or swaley cross bedding and parallel bedding, （D）calcarenite with parallel bedding, （E）calcarenite with wavy cross bedding, （F）calcisilite with horizontal bedding and （G）mudstone with homogeneous or horizontal bedding. These lithofacies constitutes 4 types of sedimentary succession ： （1） storm tidal succession, （2） storm current succession in subtidal zone, （3）tempestite succession for the inner shelf and （4）storm turbidite succession for the outer shelf. Wide and abundant storm deposits may indicate that sedimentary environments from tidal flat to shelf of low latitude zone（5-20°）prevailed in southeastern Hubei Province in the Early Triassic.