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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
投稿时间:2020-07-03  修订日期:2020-07-30  点此下载全文
引用本文:
DOI:10.19762/j.cnki.dizhixuebao.2020288
摘要点击次数: 115
全文下载次数: 153
作者单位地址
李素萍 中国地质科学院地质研究所 北京市西城区百万庄大街26号
柳永清 中国地质科学院地质研究所 北京市西城区百万庄大街26号
旷红伟 中国地质科学院地质研究所 
彭楠 中国地质科学院地质研究所 
贾建亮 中国地质科学院地质研究所 
王涛 中国地质科学院地质研究所 
中文摘要: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井下部岩心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,共同显示着下中侏罗统温暖潮湿的气候环境与含煤岩系至上侏罗统酷热干旱环境与戈壁沙漠沉积体系的演化规律。
中文关键词:银额盆地  侏罗纪  孢粉植物群  地层时代  古气候
 
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
Author NameAffiliationAddress
Li Suping Institute of Geology, Chinese Academy of Geological Sciences 北京市西城区百万庄大街26号
Liu Yongqing Institute of Geology, Chinese Academy of Geological Sciences 北京市西城区百万庄大街26号
Kuang Hongwei Institute of Geology, Chinese Academy of Geological Sciences 
Peng Nan Institute of Geology, Chinese Academy of Geological Sciences 
Jia Jianliang Institute of Geology, Chinese Academy of Geological Sciences 
Wang Tao Institute of Geology, Chinese Academy of Geological Sciences 
Abstract:Due to the lack of outcrop data in the Yingen-Ejin Basin, the biostratigraphy was poorly studied. In addition, the stratigraphic division of drill cores and the corresponding age of oil and gas reservoir are still under controversial, either as Mesozoic or Late Paleozoic. In purpose of providing palynological evidences for the stratigraphic correlation of Yingen-Ejin Basin, pollen analysis was carried out to the bottom part of MED-1 core samples from Wuzhuer depression, western Yingen-Ejin Basin. 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 nonstriate bisaccate taxa are diverse and abundant, while the striate bisaccate pollen only appears sporadically. Fern spores are dominated by Osumundacidite, and with the frequently 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 Quadraeculina and Cyathidites show an increase than 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 turns to 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, which providing new paleontological evidences for the stratigraphic correlation in Yingen-Ejin Basin. Yet, 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 eolian deposits of extremely hot environments.
keywords:Yingen-Ejin Basin  Jurassic  palynoflora  stratigraphy and geochronology  paleoclimate
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