东海盆地西湖凹陷天台区始新世平湖组风暴岩的发现及其地质意义  

Discovery and Geological Significance of Eocene Pinghu Formation Tempestites in Tiantai Area,Xihu Sag,East China Sea Basin

作　　者：何玉平 He Yuping(Research Instituteof CNOOC Ltd.,Beijing 100028,China)

机构地区：[1]中海油研究总院有限责任公司,北京100028

出　　处：《吉林大学学报（地球科学版）》2020年第2期500-508,共9页Journal of Jilin University：Earth Science Edition

基　　金：国家科技重大专项(2016ZX04024-002)。

摘　　要：风暴岩对于古地理和古环境具有良好的指相意义。东海盆地西湖凹陷天台区始新世平湖组发育典型的风暴岩。通过详细的岩心观察,发育的风暴沉积标志主要有冲刷-充填构造、风暴撕扯构造和丘状-洼状交错层理构造等。根据风暴岩垂向上的组合特征及沉积构造差异,识别出了近源和远源两种风暴沉积类型,分别指示了不同的沉积背景:近源风暴岩表现为不完整的风暴岩垂向沉积序列,呈风暴砾屑层段(A)+泥岩段(E)叠加,为潮坪潮下带沉积;远源风暴岩具完整和不完整的风暴岩垂向沉积序列,以粒序段(B)+平行层理段(C)+丘状(洼状)层理段(D)叠加为特征,属浅海陆棚沉积。风暴层序自下而上沉积环境为浅海陆棚→潮坪,风暴岩的分布差异表明形成环境向上变浅的沉积特征。该发现为本区古环境的演变提供了重要依据。The tempestites are developed in Eocene Pinghu Formation in Tiantai area in Xihu sag,and the discovery of tempestites has great paleo-graphical and paleo-environmental significances. According to core observation, the storm-generated sedimentary structures are identified, including scouring-filling structure, storm tearing structure, and hummocky cross-stratifications, etc. Through analyzing the lithofacies and sedimentary structures, two types of tempestites, near source and far source, are distinguished. The near source tempestites show incomplete storm sedimentary sequence units, and are dominated by storm-generated grave layers(A)+mud beds(E), indicating sedimentary environment of subtidal zone of tidal flat;while the far source tempestites show incomplete or complete storm sedimentary sequence units, and are dominated by graded members(B)+parallel laminations(C)+hummocky cross-stratifications(D), indicating shallow near storm wave base environment. The sequential depositional evolution of tempestites is from shallow sea shelf to tidal flat upwardly. The discovery of tempesites in the study area provides an important basis for the research of the evolution of paleo-environment.

关 键 词：风暴岩 沉积序列 古环境 平湖组 西湖凹陷 

分 类 号：P534.53[天文地球—古生物学与地层学]