【摘要】：研究區(qū)古近紀(jì)十分發(fā)育。本文以野外實(shí)測(cè)剖面為基礎(chǔ),運(yùn)用巖石地層、生物地層及年代地層的方法對(duì)該區(qū)古近紀(jì)地層進(jìn)行了地層劃分對(duì)比,并近一步對(duì)其沉積體系及古氣候進(jìn)行分析研究。本文在成都地層小區(qū)共選擇了八條具代表性的實(shí)測(cè)和觀測(cè)剖面進(jìn)行研究。根據(jù)巖石地層劃分的方法和原則,結(jié)合前人對(duì)巖石地層劃分的研究,本文提出了合理的巖石地層劃分方案,即將研究區(qū)古近紀(jì)地層自下而上劃分為大溪礫巖(KEd)、名山組(E1-2m)和蘆山組(E3l),其中大溪礫巖中上段與名山組、蘆山組為同時(shí)異相沉積,并詳細(xì)描述了各巖石地層單位的巖性組合特征、地層厚度、接觸關(guān)系及橫向變化特征。根據(jù)研究區(qū)內(nèi)古近紀(jì)地層古生物化石的分布及組合特征,建立了三個(gè)生物組合帶,即介形蟲(chóng)Limnocythere yaanensis-Cyprinotus subquadratus-Homoeucypris bacerusa組合帶;輪藻Peckichara longa-Stephanochara funingensis-Gyrogona qianjiangic組合帶和孢粉Pentapollenites-Rhoipites-Cedripites組合帶,并根據(jù)各生物組合帶的時(shí)限和層位進(jìn)行區(qū)域?qū)Ρ?認(rèn)為名山組的年代地層應(yīng)為古新統(tǒng)-始新統(tǒng),名山組一段大致與古新統(tǒng)相當(dāng),名山組二段大致與始新統(tǒng)相當(dāng)。而蘆山組主要為漸新統(tǒng),可能包括少量始新統(tǒng)上部地層。通過(guò)ESR法測(cè)年齡認(rèn)為大溪礫巖是上白堊統(tǒng)至古新統(tǒng),其頂界可能到漸新統(tǒng)。根據(jù)研究區(qū)各剖面的巖性組合特征、沉積構(gòu)造及古生物化石等資料的綜合分析,對(duì)各實(shí)測(cè)剖面進(jìn)行沉積體系分析,將研究區(qū)川西雅安地區(qū)古近紀(jì)地層劃分為一個(gè)沉積體系組,即陸相沉積體系組;陸相沉積體系組分為沖積扇相和湖泊相兩種類(lèi)型,沖積扇相分為扇中亞相和扇端亞相;湖泊相分為濱湖亞相和淺湖亞相。在研究區(qū)地層劃分對(duì)比及沉積體系分析的基礎(chǔ)上,總結(jié)得出了川西古近系的沉積相模式圖及古近紀(jì)古新世-漸新世巖相古地理圖。通過(guò)對(duì)地球化學(xué)、沉積學(xué)、古植物學(xué)及古地理學(xué)的綜合研究,進(jìn)行該區(qū)古近系古氣候特征初步研究,表明從古新世-始新世名山期到漸新世蘆山期,總體為干旱的熱帶-亞熱帶氣候,從早到晚其干旱炎熱程度降低。
[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.
【學(xué)位授予單位】：成都理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類(lèi)號(hào)】：P534.6;P532

【參考文獻(xiàn)】

相關(guān)期刊論文 前1條

1 茍宗海;四川天全、蘆山、寶興地區(qū)名山組地層特征[J];四川地質(zhì)學(xué)報(bào);1992年03期

，

本文編號(hào)：2462652