地质学报2018，Vol.92Issue(3)：466-481,16.
合肥盆地安参1井前侏罗纪基底地层的孢粉组合特征与时代归属
Characteristics and Age Assignment of the Sporo-Pollen Assemblages of Pre-Jurassic Basement Strata in Well Ancan-1, Hefei Basin
摘要
Abstract
Well Ancan-1 is the deepest parameter well in the Hefei basin,northern margin of the Dabie orogenic belt.The primary lithology of the drilled Pre-Jurassic basement strata,with a thickness of more than 1000 m,consists predominantly of dark mudstone,without coal streak,coal seam or limestone,which makes it difficult to compare with the strata of North China craton and the Dabie orogen belt.For lack of megafossils record and definite dating data,the age assignment of basin basement has been in dispute,which restricts deep understanding of the geological information related to this particular formation.In order to further clarify the depositional age of the peculiar strata,a large number of cores and debris samples in well An'can-1 (4160～5152m) were studied,and 23 genera,51 species and 647 sporo-pollen fossils have been identified.According to the analysis of genera,content change and vertical variation of sporo-pollen fossils,this study classified the sporo-pollen into two assemblages as follows (in a descending order):assemblage Ⅰ,Densosporites reynoldburgensis-Laevigatosporites perminutus,and assemblage Ⅱ,Triquitrites-Macrotorispora media.In sporo-pollen assemblage Ⅰ,fern spores are predominant,accounting for 87.67％ on average,including Laevigatosporites perminutus,Lycospora rotunda,Patellisporites meishanesis and others.Gymnospermous pollen grains are completely Florinites.In assemblage Ⅱ,the average content of fern spores decreased to 53.7％.Among them,the contents of some spores (such as Leiotriletes adnatus,Triquitrites and Crassipora) decline,with the Lycospora rotunda even disappeared.In addition,there existed Macrotorispora as typical element.The content and richness of gymnospermous pollen,esepically Cordaitina,increased significantly.Comparison analysis of these assemblages with those in other areas in North China shows that the two sporo-pollen assemblages mentioned above are similar to the sporo-pollen in the Taiyuan and the Upper Shihezi formations of late Paleozoic in the north of China,respectively,and are consistent with Early Cathaysia flora and Middle-Late Cathaysia Flora respectively.These features reflect a process of prosperity and enrichment of gymnospermae.The geological time of the two sporo-pollen assemblages should be the late Late Carboniferous to early Early Permian and the Late Permian,respectively.This study provides not only direct evidence for the existence of the Carboniferous-Permian in Pre-Jurassic basement strata in Well Ancan 1,but also new materials for sedimentary environment and paleoclimate analysis of the Hefei Basin.关键词
合肥盆地基底/孢粉组合/地层划分/二叠系/安参1井Key words
The basement of Hefei basin/Sporo-pollen assemblages/stratigraphic division/Permian/Well Ancan-1引用本文复制引用
苗慧心,孙福利,张交东,周新桂,刘德良,李振生,宋立才,曾秋楠,刘旭锋,毕彩芹..合肥盆地安参1井前侏罗纪基底地层的孢粉组合特征与时代归属[J].地质学报,2018,92(3):466-481,16.基金项目
本文为国家自然科学基金面上项目D0206-41372123、41372194、41072080和国家重大科技专项“大型油气田和煤层气开发”任务联合资助的成果. （）
