塔里木盆地西部巴什布拉克剖面晚始新世—早渐新世介形类化石及其对海退事件的约束

发布时间：2018-03-16 18:07

  本文选题：介形虫　切入点：海退　出处：《中国地质大学(北京)》2017年硕士论文　论文类型：学位论文

【摘要】：新生代全球发生了一系列重大地质事件,其中青藏高原的隆升和特提斯海的消亡备受关注。塔里木盆地是我国最大的中、新生代沉积盆地,其西部发育广泛的海相地层。特提斯海何时从塔里木盆地西部退出,目前仍存在较大争议。巴什布拉克剖面位于海退的主通道,海相沉积良好,具有连续的海、陆相过渡沉积,微体化石含量丰富,可为海退事件的研究提供良好载体。本文对巴什布拉克剖面涉及最后海退的关键层位——巴什布拉克组进行地层描述、微体化石采样和分析。在巴什布拉克组发现含量丰富的介形类、有孔虫(浮游有孔虫)、腹足类、鱼牙等微体化石,对其中的介形虫化石进行了系统鉴定和分析。经鉴定,巴什布拉克组野外样品中发现介形类微体化石12属16种。根据介形类的生物面貌、化石分布组合以及垂向地层变化特征,对巴什布拉克组开展生物地层学研究,建立介形类化石组合序列,并划分出3个组合带:1)Cytherella evexa-Haplocytheridea unispinata-Leguminocythereis vesca组合带;2)Cytheretta circumspect组合带;3)Haplocytheridea schirabadensis-Ruggieria rischtanensis-Haplocythereidea innae组合带。根据介形类生物地层,并结合其他证据,推断巴什布拉克组的时代应为晚始新世,但不排除四、五段进入早渐新世的可能。介形类古生态分析表明其属于典型海相分子,指示滨浅海环境。根据介形类特征,结合沉积学等证据,初步认为最高海相层的层位在巴什布拉克组四段顶部,在此之上尚未见海相化石,表明特提斯海在研究区于巴四段顶部沉积时期开始退出,时代为晚始新世,也可能已进入早渐新世。
[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.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：Q915.2;P534.6
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本文编号：1621062