川西古近纪地层划分对比、沉积体系及古气候分析
发布时间：2019-04-22 07:55
【摘要】：研究区古近纪十分发育。本文以野外实测剖面为基础,运用岩石地层、生物地层及年代地层的方法对该区古近纪地层进行了地层划分对比,并近一步对其沉积体系及古气候进行分析研究。本文在成都地层小区共选择了八条具代表性的实测和观测剖面进行研究。根据岩石地层划分的方法和原则,结合前人对岩石地层划分的研究,本文提出了合理的岩石地层划分方案,即将研究区古近纪地层自下而上划分为大溪砾岩(KEd)、名山组(E1-2m)和芦山组(E3l),其中大溪砾岩中上段与名山组、芦山组为同时异相沉积,并详细描述了各岩石地层单位的岩性组合特征、地层厚度、接触关系及横向变化特征。根据研究区内古近纪地层古生物化石的分布及组合特征,建立了三个生物组合带,即介形虫Limnocythere yaanensis-Cyprinotus subquadratus-Homoeucypris bacerusa组合带;轮藻Peckichara longa-Stephanochara funingensis-Gyrogona qianjiangic组合带和孢粉Pentapollenites-Rhoipites-Cedripites组合带,并根据各生物组合带的时限和层位进行区域对比,认为名山组的年代地层应为古新统-始新统,名山组一段大致与古新统相当,名山组二段大致与始新统相当。而芦山组主要为渐新统,可能包括少量始新统上部地层。通过ESR法测年龄认为大溪砾岩是上白垩统至古新统,其顶界可能到渐新统。根据研究区各剖面的岩性组合特征、沉积构造及古生物化石等资料的综合分析,对各实测剖面进行沉积体系分析,将研究区川西雅安地区古近纪地层划分为一个沉积体系组,即陆相沉积体系组;陆相沉积体系组分为冲积扇相和湖泊相两种类型,冲积扇相分为扇中亚相和扇端亚相;湖泊相分为滨湖亚相和浅湖亚相。在研究区地层划分对比及沉积体系分析的基础上,总结得出了川西古近系的沉积相模式图及古近纪古新世-渐新世岩相古地理图。通过对地球化学、沉积学、古植物学及古地理学的综合研究,进行该区古近系古气候特征初步研究,表明从古新世-始新世名山期到渐新世芦山期,总体为干旱的热带-亚热带气候,从早到晚其干旱炎热程度降低。
[Abstract]:The study area developed very well in Paleogene. Based on the field measured profiles, this paper uses the methods of lithostratigraphy, biostratigraphy and chronostratigraphy to make stratigraphic division and correlation of the Paleogene strata in this area, and makes an analysis of its sedimentary system and paleoclimate in the next step. In this paper, a total of eight representative observed and observed sections have been selected in Chengdu stratigraphic plot to carry on the research. According to the method and principle of lithostratigraphic division, combined with previous studies on lithostratigraphic division, this paper puts forward a reasonable lithostratigraphic division scheme, that is to say, the Paleogene strata in the study area are divided from the bottom to the top into the Daxi conglomerate (KEd),. Mengshan formation (E1 / 2m) and Lushan formation (E3l), in which the middle-upper member of Daxi conglomerate and Mingshan formation and Lushan formation are depositional at the same time, and the lithologic assemblage characteristics and stratigraphic thickness of each lithostratigraphic unit are described in detail, and the lithologic assemblage characteristics and stratigraphic thickness of each lithostratigraphic unit are described in detail. Contact relationship and lateral variation characteristics. According to the distribution and assemblage characteristics of Paleogene paleontology fossils in the study area, three biological assemblages, namely the Limnocythere yaanensis-Cyprinotus subquadratus-Homoeucypris bacerusa assemblage zone of Ostractylodes, have been established. Peckichara longa-Stephanochara funingensis-Gyrogona qianjiangic assemblage zone and sporopollen Pentapollenites-Rhoipites-Cedripites assemblage zone, and regional correlation according to the time limit and horizon of each biological assemblage zone, it is concluded that the chronostratigraphy of the Mingshan formation should be Paleocene-Eocene. The first member of the Mingshan formation is about the same as the Paleocene, and the second member of the Mingshan formation is about the same as the Eocene. The Lushan formation is mainly Oligocene, which may include a small amount of Eocene upper strata. By means of ESR dating, Daxi conglomerate is considered to be from Upper Cretaceous to Paleocene, and its top boundary may be to Oligocene. Based on the comprehensive analysis of lithologic assemblage characteristics, sedimentary structure and paleontology fossil data of each section of the study area, the sedimentary system of each measured section is analyzed, and the Paleogene strata in Yaan area, western Sichuan Province, are divided into a sedimentary system group. Continental sedimentary system formation; Continental sedimentary system can be divided into alluvial fan facies and lacustrine facies, alluvial fan facies can be divided into middle fan subfacies and fan end subfacies, lacustrine facies can be divided into shore lacustrine subfacies and shallow lacustrine subfacies. On the basis of stratigraphic division, correlation and sedimentary system analysis, the sedimentary facies model map and paleogeographic map of Paleogene-Oligocene lithofacies in western Sichuan are summarized. Based on the comprehensive study of geochemistry, sedimentology, palaeobotany and palaeogeography, the palaeogene paleoclimate characteristics of this area are studied. The results show that the paleogene paleoclimate is from Paleocene-Eocene to Oligocene Lushan period. The whole climate is arid tropical-subtropical climate, and the degree of drought and heat decreases from morning to night.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P534.6;P532
本文编号：2462652
[Abstract]:The study area developed very well in Paleogene. Based on the field measured profiles, this paper uses the methods of lithostratigraphy, biostratigraphy and chronostratigraphy to make stratigraphic division and correlation of the Paleogene strata in this area, and makes an analysis of its sedimentary system and paleoclimate in the next step. In this paper, a total of eight representative observed and observed sections have been selected in Chengdu stratigraphic plot to carry on the research. According to the method and principle of lithostratigraphic division, combined with previous studies on lithostratigraphic division, this paper puts forward a reasonable lithostratigraphic division scheme, that is to say, the Paleogene strata in the study area are divided from the bottom to the top into the Daxi conglomerate (KEd),. Mengshan formation (E1 / 2m) and Lushan formation (E3l), in which the middle-upper member of Daxi conglomerate and Mingshan formation and Lushan formation are depositional at the same time, and the lithologic assemblage characteristics and stratigraphic thickness of each lithostratigraphic unit are described in detail, and the lithologic assemblage characteristics and stratigraphic thickness of each lithostratigraphic unit are described in detail. Contact relationship and lateral variation characteristics. According to the distribution and assemblage characteristics of Paleogene paleontology fossils in the study area, three biological assemblages, namely the Limnocythere yaanensis-Cyprinotus subquadratus-Homoeucypris bacerusa assemblage zone of Ostractylodes, have been established. Peckichara longa-Stephanochara funingensis-Gyrogona qianjiangic assemblage zone and sporopollen Pentapollenites-Rhoipites-Cedripites assemblage zone, and regional correlation according to the time limit and horizon of each biological assemblage zone, it is concluded that the chronostratigraphy of the Mingshan formation should be Paleocene-Eocene. The first member of the Mingshan formation is about the same as the Paleocene, and the second member of the Mingshan formation is about the same as the Eocene. The Lushan formation is mainly Oligocene, which may include a small amount of Eocene upper strata. By means of ESR dating, Daxi conglomerate is considered to be from Upper Cretaceous to Paleocene, and its top boundary may be to Oligocene. Based on the comprehensive analysis of lithologic assemblage characteristics, sedimentary structure and paleontology fossil data of each section of the study area, the sedimentary system of each measured section is analyzed, and the Paleogene strata in Yaan area, western Sichuan Province, are divided into a sedimentary system group. Continental sedimentary system formation; Continental sedimentary system can be divided into alluvial fan facies and lacustrine facies, alluvial fan facies can be divided into middle fan subfacies and fan end subfacies, lacustrine facies can be divided into shore lacustrine subfacies and shallow lacustrine subfacies. On the basis of stratigraphic division, correlation and sedimentary system analysis, the sedimentary facies model map and paleogeographic map of Paleogene-Oligocene lithofacies in western Sichuan are summarized. Based on the comprehensive study of geochemistry, sedimentology, palaeobotany and palaeogeography, the palaeogene paleoclimate characteristics of this area are studied. The results show that the paleogene paleoclimate is from Paleocene-Eocene to Oligocene Lushan period. The whole climate is arid tropical-subtropical climate, and the degree of drought and heat decreases from morning to night.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P534.6;P532
【参考文献】
相关期刊论文 前1条
1 苟宗海;四川天全、芦山、宝兴地区名山组地层特征[J];四川地质学报;1992年03期
，本文编号：2462652
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