本文選題：介形蟲　切入點(diǎn)：海退　出處：《中國地質(zhì)大學(xué)(北京)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：新生代全球發(fā)生了一系列重大地質(zhì)事件,其中青藏高原的隆升和特提斯海的消亡備受關(guān)注。塔里木盆地是我國最大的中、新生代沉積盆地,其西部發(fā)育廣泛的海相地層。特提斯海何時(shí)從塔里木盆地西部退出,目前仍存在較大爭議。巴什布拉克剖面位于海退的主通道,海相沉積良好,具有連續(xù)的海、陸相過渡沉積,微體化石含量豐富,可為海退事件的研究提供良好載體。本文對巴什布拉克剖面涉及最后海退的關(guān)鍵層位——巴什布拉克組進(jìn)行地層描述、微體化石采樣和分析。在巴什布拉克組發(fā)現(xiàn)含量豐富的介形類、有孔蟲(浮游有孔蟲)、腹足類、魚牙等微體化石,對其中的介形蟲化石進(jìn)行了系統(tǒng)鑒定和分析。經(jīng)鑒定,巴什布拉克組野外樣品中發(fā)現(xiàn)介形類微體化石12屬16種。根據(jù)介形類的生物面貌、化石分布組合以及垂向地層變化特征,對巴什布拉克組開展生物地層學(xué)研究,建立介形類化石組合序列,并劃分出3個(gè)組合帶:1)Cytherella evexa-Haplocytheridea unispinata-Leguminocythereis vesca組合帶;2)Cytheretta circumspect組合帶;3)Haplocytheridea schirabadensis-Ruggieria rischtanensis-Haplocythereidea innae組合帶。根據(jù)介形類生物地層,并結(jié)合其他證據(jù),推斷巴什布拉克組的時(shí)代應(yīng)為晚始新世,但不排除四、五段進(jìn)入早漸新世的可能。介形類古生態(tài)分析表明其屬于典型海相分子,指示濱淺海環(huán)境。根據(jù)介形類特征,結(jié)合沉積學(xué)等證據(jù),初步認(rèn)為最高海相層的層位在巴什布拉克組四段頂部,在此之上尚未見海相化石,表明特提斯海在研究區(qū)于巴四段頂部沉積時(shí)期開始退出,時(shí)代為晚始新世,也可能已進(jìn)入早漸新世。
[Abstract]:A series of major geological events occurred in the Cenozoic world, in which the uplift of the Qinghai-Tibet Plateau and the extinction of the Tethys Sea have attracted much attention. The Tarim Basin is the largest Mesozoic and Cenozoic sedimentary basin in China. The Tethys Sea withdrew from the western part of the Tarim Basin, which is still controversial. The Bashburak section is located in the main passage of the regressive sea, with good marine deposits and continuous marine and continental transitional deposits. The microfossils are rich in fossils, which can provide a good carrier for the study of regression events. In this paper, the Bashburak formation, the key horizon of the last regression, is described in this paper. Microfossils were sampled and analyzed. The rich ostracods, foraminifera (planktonic foraminifera, gastropods, fish teeth, etc.) were found in the Bashburak formation. The ostracods were systematically identified and analyzed. In the field samples of the Bashburak formation, 16 species of microfossils belonging to 12 genera have been found. According to the biological features, fossil assemblages and vertical stratigraphic changes of the ostracods, biostratigraphic studies have been carried out in the Bashburak formation. The ostracoid fossil assemblage sequence was established, and three assemblages were divided into three assemblages: 1 / 1 Cytherella evexa-Haplocytheridea unispinata-Leguminocythereis vesca assemblage 2 / 2 of the Cytheretta circumspect assemblage of Haplocytheridea schirabadensis-Ruggieria rischtanensis-Haplocythereidea innae. According to the ostracoid biostratigraphy and combined with other evidences, it is inferred that the age of the Bashburak formation should be the late Eocene. But it is not ruled out that the 4th and 5th member entered the early Oligocene epoch. The analysis of ostracoid paleoecology shows that it belongs to the typical marine elements and indicates the coastal shallow sea environment. According to the characteristics of the ostracoda, combined with the evidence of sedimentology and so on, It is preliminarily considered that the strata of the highest marine strata are located at the top of the fourth member of the Bashburak formation, on which no marine fossils have been found, indicating that the Tethys Sea began to withdraw during the sedimentary period from the top of the Ba fourth member in the study area, and the age was the late Eocene. It may also have entered the early Oligocene.
【學(xué)位授予單位】：中國地質(zhì)大學(xué)(北京)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：Q915.2;P534.6
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本文編號：1621062