银额盆地侏罗纪孢粉植物群的发现及其地层时代意义——以蒙额地1井为例  

Palynoflora from the Jurassic of Yingen-Ejin basin, NW China and its implications for the stratigraphy and geochronology——a case study on MED-1 drill core

作　　者：李素萍[1,2] 柳永清 旷红伟[1] 彭楠[1,2] 贾建亮[1] 王涛 LI Suping;LIU Yongqing;KUANG Hongwei;PENG Nan;JIA Jianliang;WANG Tao(Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China;Key Laboratory of Stratigraphy and Paleontology,Ministry of Natural Resources,Beijing 100037,China)

机构地区：[1]中国地质科学院地质研究所,北京100037 [2]自然资源部地层与古生物重点实验室,北京100037

出　　处：《地质学报》2021年第5期1382-1399,共18页Acta Geologica Sinica

基　　金：中国地质调查局项目(编号DD20190005,DD20190397);国家自然科学基金项目(编号41688103,41672111);国家重点研发计划(编号2018YFC0604201)联合资助的成果。

摘　　要：由于露头资料缺乏,银额盆地生物地层研究一直较为薄弱,钻井的地层时代划分及主要油气产层时代归属存在较大争议。为了厘清银额盆地钻井所揭示的油气产层的地层时代,本研究对位于盆地西部乌珠尔坳陷的蒙额地1井下部岩芯样品开展了孢粉学研究工作。根据孢粉类群及其含量的变化,划分了2个孢粉组合:Osmundacidites-Deltoidospora-nonstriate bisaccate组合和Classopollis-Cyathidites-Quadraeculina组合。第一组合中裸子植物花粉和蕨类植物孢子含量相当,裸子植物花粉中无肋纹的双气囊花粉出现最为频繁,且多样性较高,并零星出现有具肋纹双气囊花粉,蕨类植物孢子以Osmundacidites为主,其他常见类群包括Lycopodiumsporites、Deltoidospora、Neoraistrickia等,均为我国侏罗纪常见属种,孢粉组合指示的地层时代为早侏罗世晚期,也可能下延至早侏罗世中期,气候温暖湿润;第二组合以Classopollis的高含量为特征,Quadraeculina和Cyathidites较第一组合含量增加,且未出现任何白垩纪的特征分子,反映了中侏罗世晚期的孢粉组合特征,气候由上述的温暖湿润转变为炎热干旱。根据本文的孢粉组合特征,原依据叶肢介化石定为上二叠统的地层宜重新厘定为中下侏罗统。同时,厘定的侏罗系在整个中国北方具有良好的可对比性,共同显示由早中侏罗世温暖潮湿的气候环境与含煤岩系向晚侏罗世酷热干旱环境与戈壁沙漠沉积体系的演化规律。The lack of outcrops has limited biostratigraphic studies in the Yingen-Ejin basin. Also controversial is the stratigraphic division of drill cores and the corresponding age of oil and gas reservoir, if they belong to Mesozoic or Late Paleozoic. Pollen analysis was carried out to the bottom part of MED-1 core samples from Wuzhuer depression, western Yingen-Ejin Basin to provide palynological evidence for their stratigraphic correlation. According to the variations of the sporopollen taxa and their percentages, two palynological assemblages were recognized, the Osmundacidites-Deltoidospora-nonstriate bisaccate assemblage and the Classopollis-Cyathidites-Quadraeculina assemblage. In the first assemblage, the proportions of gymnosperms and ferns are close to equal. The nonstriated bisaccate taxa are diverse and abundant, while the striate bisaccate pollen grains only appear sporadically. Fern spores are dominated by Osumundacidites, with the frequent appearances of Lycopodiumsporites, Deltoidospora, Neoraistrickia etc. Most of these taxa are common in Jurassic. The geological age revealed by the first palynological assemblage should be middle to late Early Jurassic, and the palynomorphs indicate a warm and humid climate at that time. Among the second assemblage, Classopollis becomes predominant, and both Quadraeculina and Cyathidites show an increase compared to the last assemblage. No typical taxa of Cretaceous appear in this assemblage. The geological age should be assigned to late Middle Jurassic, and the climate turned hot and dry during this period. According to the characteristics of the sporopollen assemblages, the strata previously designated as Upper Permian on the basis of Estherians fossils was redefined to be the Middle-Lower Jurassic, thus providing new paleontological evidences for the stratigraphic correlation in Yingen-Ejin basin. The revised geochronology and stratigraphy of Jurassic are well correlated in North China, and consistent with the evolution from coal rocks in humid and warm settings to e

关 键 词：侏罗纪 孢粉植物群 地层时代 古气候 银额盆地 

分 类 号：P618.13[天文地球—矿床学]