黔东镇远地区早寒武世清虚洞组潮坪风暴沉积特征及古地理意义  

Sedimentary Characteristics of Tidal Storm Deposit of Early Cambrian Qingxudong Formation in the Zhenyuan Area,Eastern Guizhou and Its Palaeogeographical Implications

作　　者：马志鑫[1] 张万平[1] 刘伟[1] 李波[2] 

机构地区：[1]成都地质矿产研究所,成都610081 [2]中国地质大学(武汉)生物地质与环境地质国家重点实验室,武汉430074

出　　处：《沉积学报》2012年第5期787-794,共8页Acta Sedimentologica Sinica

基　　金：中国地质调查局地质调查工作项目<扬子陆块周缘铅锌矿成矿带基础地质综合研究>(编号:1212011085168)资助

摘　　要：黔东镇远地区早寒武世(相当于2008国际地层年表中的寒武纪第二世)清虚洞组发现类型丰富、特征典型的风暴沉积标志。侵蚀底面、粗粒滞留沉积、粒序层、波状层理、韵律层理等沉积组构明显,而丘状层理不发育。通过对金盆剖面和溜沙关剖面详细的野外观察及室内分析,识别出三种类型的风暴沉积序列。研究区风暴沉积的背景沉积为灰色纹层状灰岩,见波状层理、鸟眼构造等,指示潮坪环境。综合分析得出,镇远地区的风暴沉积属于潮坪风暴沉积。这丰富了湘西黔东地区早寒武世清虚洞组风暴沉积的类型。风暴沉积的发现也为研究区早寒武世位于赤道附近的低纬度区域提供了间接的证据。Storm deposits with typical features of were found in the Qingxudong Formation, Lower Cambrian （corre- sponding to Series 2 of Cambrian） in Zhenyuan area, eastern Guizhou Province. Based on field observation on the Jin- pen Section and Liushaguan Section and laboratory analysis, sedimentary structures of storm deposit, such as erosion surface, coarse lag deposits, graded bedding, ripple beddings and rhythmic lamination, are present in the succession, excluding hummocky cross-stratification. Particularly, the lag-suspension deposit couple is evident, winnowed coarse lag deposits occur in the below with an overlying fine laminated bed. Three types of storm deposit sequences with dif- ferent vertical stacking patterns were identified. Sequence I consists of the coarse lag deposits, ripple beddings and rhythmic lamination upwards. The coarse lag deposits which are composed of gravels, intraelasts and ooids are the predominant parts. Sequence 11 consists of the graded bedding and ripple beddings, and including wavy erosion sur- face in the bottom. Sequence 131 is responsible for multi-stage small scale storm, including lag deposits and ripple beddings. The background deposit is gray laminated limestone, with ripple bedding, bird~ eye structure, indicating tidal flat environment. In summary, the storm deposits in Zhenyuan is attributed to tidal flat storm deposit, that enrich the style of storm deposits of Qingxudong Formation, early Cambrian, in eastern Guizhou and western Hunan. The distribution pattern of storm deposit of Qingxudong Formation, in eastern Guizhou and western Hunan was preliminari- ly summarized based on the previous work and this study. The discovery of storm deposits reflects indirectly the study area should be located in the low latitudes near the equator during the Early Cambrian.

关 键 词：风暴沉积 潮坪 寒武纪 清虚洞组 黔东 

分 类 号：P512.2[天文地球—地质学] P534.41