兰州大学机构库 >地质科学与矿产资源学院
甘肃永昌山西组植物化石微细构造及孢粉学研究
Alternative TitleFossil Plants with microstructures and Palynology Study from Shanxi Formation in Yongchang, Gansu
王雪莲
Subtype博士
Thesis Advisor孙柏年
2020-07-29
Degree Grantor兰州大学
Place of Conferral兰州
Degree Name理学博士
Degree Discipline古生物学与地层学
Keyword甘肃 早二叠世 植物化石 繁殖器官 角质层 孢粉化石 古地理 古气候
Abstract二叠纪是全球冰室向温室转变的重要时期,陆生植物繁盛,气候分带特征颇为明显,根据环境和植物类群可分为四大植物区系,在此期间古气候和植被面貌都逐渐发生着变化,二叠纪末期的大灭绝事件使得生态环境发生了彻底的改变,因此了解和探讨该时期生物演变和环境特征具有重要的意义。植物大化石是植物演化最直接有效的证据,孢粉是高等陆生植物的繁殖器官,具有数量大易保存的优点,对环境和气候的响应最直接、最敏感,二者是研究地史时期植物群特征以及环境变化的重要依据。甘肃永昌地区发育较好的二叠纪陆相地层,植物化石丰富,通过系统研究永昌山西组中的植物大化石和孢粉组合,为研究中国西北华夏植物群的植物多样性演变和古环境特征提供了充足的证据。 在甘肃永昌山西组中采集了大量植物化石,对保存较好的压型化石进行了宏观学和微细构造的综合分析,类型包括营养叶和繁殖器官,结合角质层分析法、原位孢粉分析法、聚类分析法以及主成分分析法,共鉴定和描述了植物化石22属40种,建立了4个新属8个新种(包括已发表的2个新种)。采用传统的孢粉分析法-盐酸和氢氟酸浸泡的方式对山西组中43件孢粉样进行处理,鉴定并描述了孢粉化石53属78种,根据孢粉丰度的变化建立了3个组合带。结合大量化石记录以及古板块资料对部分属种的起源和古地理分布特征进行了深入探讨,同时结合植物大化石组合特征、角质层分析结果以及孢粉组合特征对植物群性质、地质时代以及古环境进行综合分析。 详细研究了蕨类植物中鳞木科、芦木科、真蕨纲和裸子植物中的种子蕨纲、科达纲以及种子等多种压型化石的形态特征,结合微细构造特征对他们进行了准确的分类鉴定,包括Lepidostrobus、Calamites、Macrostachya、Asterotheca、Pecopteris、Cladophlebis、Sphenopteris、Mariopteris、Taeniopteris、Neuropteris、Neuropteridium、Alethopteris、Cordaianthus、Samaropsis、Acanthocarpus以及Carpolithus。鳞木科的孢子囊穗保存为由大量孢子叶环绕的穗轴横截面,建立了一新种Lepidostrobus yongchangensis sp. nov.,与美国伊利诺斯州晚石炭世地层中发现的鳞孢穗形态相似。 对芦木科的茎髓部位和孢穗进行了详细分析,将孢穗定为Macrostachya sp.,结合芦木类植物大量化石记录,推测该类植物起源于中国晚泥盆世的华南地区,至石炭-二叠纪期间遍布欧美地区乃至中国,并且Calamostachys是其它孢穗类型的祖先类群。根据孢子囊穗形态以及原位孢子特征,建立了瓢叶目一新属种Hexistrobus yongchangensis gen. et sp. nov.,推测该类植物起源于泥盆纪的欧洲,在早二叠世广泛分布于中国的华夏植物群中,并且分布地区与其生态环境特征相符合。 通过对星囊蕨属一新种Asterotheca yongchangensis sp. nov.原位孢子特征的研究,结果表明该属聚合囊由四个孢子囊组成并且其演化过程可分为五个阶段结合Pecopteris与Asterotheca古生代时期的化石记录,推测我国华北地区栉羊齿属的衰退期不晚于中二叠世,并且星囊蕨属的繁盛与栉羊齿属的迁移和分布密切相关。Sphenopteris的古地理分布特征表明该属起源于我国华南晚泥盆世,其古地理分布与古构造特征表现出较强的耦合关系。研究区中发现的3种Taeniopteris的微细构特征表明该属可能是早期苏铁的叶片,并且化石记录显示Taeniopteris在中国二叠纪早期分布于华北地区,晚期广泛出现于华南地区,该属是一种喜湿热的植物。 对植物群中早期松柏类植物的枝叶和繁殖器官进行详细研究,建立了伏脂杉目(Voltziales)3个新属种:Shencladia longshoushanensis gen. et sp. nov.,Hexicladia yongchangensis gen. et sp. nov.和Palaeovoltzia minuta gen. et sp. nov.,并对其系统分类进行了详细的对比讨论同时将碳化较严重的繁殖器官标本划分为3种雄性繁殖器官类型和4个雌性生殖枝类型。雄性繁殖器官和雌性生殖枝的结构表明,早期松柏类植物的胚珠不具短柄,为Schweitzer认为早期松柏纲与科达纲无演化关系的观点提供了新的证据并且根据繁殖器官复合短枝结构的特征,早期松柏类植物雄性繁殖器官和雌性生殖枝在结构上具有等效性,这一认识支持了Hernandez-Castillo和Rothwell的观点。 根据植物大化石以及孢粉组合特征的综合分析,结果显示植物群以真蕨纲和种子蕨纲占绝对优势,松柏纲含量次之。通过与同期植物群的对比以及植物组合中华夏植物群特有分子的存在,证实了该植物群具有中期华夏植物群的面貌,并伴有欧美植物群和安加拉-亚安加拉植物群分子的渗入,推测研究区的地质时代应该属于早二叠世中晚期的亚丁斯克期-空谷期(Artinskian-Kungurian)。 古环境分析表明,大量真蕨纲和种子蕨纲化石角质层特征存在共性,即营养叶均呈全缘,上表皮较下表皮厚且气孔器无明显下陷,指示了该类植物均生长于湿润的气候环境中。Taeniopteris新种以及部分松柏纲植物繁殖器官角质层上着生的毛状体特征表明该时期植物已经具备了防止水分蒸发以及保护繁殖器官的结构功能,并且该结构指示了植物化石属于近原地埋藏。另外,植物群中占绝对优势的真蕨纲和种子蕨纲均生存于热-温带的湿润环境中,石松纲、楔叶纲、瓢叶目等其它组成分子均属于喜湿且分布于水体边缘的植物,仅松柏纲属于耐旱性植物并分布于外缘地带。综合植物群组合特征以及角质层分析结果,推测早二叠世中晚期永昌植物群生存于平原低地沼泽环境中,气候具有温暖潮湿并伴有季节性干旱的特征。
Other AbstractThe important period for the global icehouseto greenhousetransformation is the Permian period, during which terrestrial plants flourished and the climate zonation characteristics are quite obvious. According to the characteristics of the environment and plant groups, it can be divided into four major floras. During this period, the paleoclimate and vegetation changed gradually. The extinction event at the end of the Permian changed the ecological environment completely. Therefore, it is of great significance to understand and discuss the biological evolution and environmental characteristics of this period. Plant fossils are the most direct and effective evidence of plant evolution. Sporopollen is the reproductive organ of higher terrestrial plants, which has the advantages of large quantity and easy preservation. It is the most direct and sensitive response to the environment and climate. These two are the important basis for studying the characteristics of flora and environmental changes in geohistory. There are abundant plant fossils in the Permian continental strata in Yongchang of Gansu Province. The systematic study of the plant fossils and sporopollen assemblages in the Shanxi Formation of Yongchang provides sufficient evidence for the study of plant diversity evolution and paleoenvironmental characteristics of Cathaysia flora in Northwest China. A large number of plant fossils were collected from the Shanxi Formation of Yongchang, Gansu Province. The macro- and microstructures analysis of the well preserved compression fossils were carried out, including vegetative leaves and reproductive organs. 22 genera and 40 species of plant fossils were identified and described by cuticle analysis, in situ pollen analysis, cluster analysis and principal component analysis, and 4 new genera and 8 new species (including 2 new species published online). 43 sporopollen samples from Shanxi Formation were treated by traditional sporopollen analysis method of hydrochloric acid and hydrofluoric acid soaking. 78 species of 53 genera of sporopollen fossils were identified and described. Three assemblages were established according to the change of sporopollen abundance. Based on a large number of fossil records and ancient block data, the origin and paleogeographic distribution characteristics of some genera and species are discussed in depth. Meanwhile, the nature, geological age and paleoenvironment of flora are comprehensively analyzed in combination with the characteristics of large fossil assemblage, cuticle analysis results and sporopollen assemblage. The morphological characteristics of many compression fossils, such as Lepidodendraceae, Calamitaceae, Filices, Pteridospermopsida, Cordaitopsida and seeds, were studied. According to the characteristics of microstructure, the accurate classification and identification are carried out, including Lepidostrobus, Calamites, Macrostachya, Asterotheca, Pecopteris, Cladophlebis, Sphenopteris, Mariopteris, Taeniopteris, Neuropteris, Neuropteridium, Alethopteris, Cordaianthus, Samaropsis, Acanthocarpus and Carpoliths. A new species Lepidostrobus yongchangensis sp. nov. has been established, which is similar to the species of Lepidostrobus found in the Pennsylvanian strata of Illinois, USA. The stem and strobilus of Calamitaceae were analyzed in detail. The strobilus was identified as Macrostachya sp., and combined with a large number of fossil records of Calamitaceae, it is inferred that this kind of plants originated in South China of Late Devonian, and spread throughout Europe, America and even China during the Carboniferous-Permian period, and Calamostachys is the ancestor group of other strobili types. A new genus Hexistrobus yongchangensis gen. et sp. nov. was established based on the morphology of strobili and in situ spore characteristics. It is speculated that this kind of Noeggerathiales originated from the Devonian in Europe and widely distributed in Cathaysia flora during the Cisuralian of China, and its distribution area is consistent with its ecological environment characteristics. The characteristics of in situ spores of Asterotheca yongchangensis sp. nov. were studied. The results show that the synangium of Asterotheca is composed of four sporangia and its evolution can be divided into five stages. According to the Paleozoic fossil records of Pecopteris and Asterotheca, it is inferred that the decline period of Pecopteris in North China was no later than the Guadalupian, and the prosperity of Asterotheca was closely related to the migration and distribution of Pecopteris. The paleogeographic distribution of Sphenopteris shows that the genus originated from the Late Devonian in South China, and its paleogeographic distribution and paleostructural characteristics show a strong coupling relationship. The microstructure characteristics of three species of Taenopteris found in the study area indicate that the genus may be the leaves of early cycad, and the fossil records show that Taenopteris distributed in North China in the Cisuralian, and widely appeared in South China in the Lopingian. The Taenopteris is a hydrothermal plant. The branches and reproductive organs of early conifers in Yongchang flora were studied in detail. Three new genera of Shencladia longshoushanensis gen. et sp. nov., Hexicladia yongchangensis gen. et sp. nov. and Palaeovoltzia minuta gen. et sp. nov. have been established. At the same time, the reproductive organs with severe carbonization were divided into three types of pollen cones and four types of ovulate cones. The structure of pollen cones and ovulate cones showed that the ovules of early conifers did not have short stalks, which provided a new evidence for Schweitzer&rsquos view that there was no evolutionary relationship between early conifers and Cordaitopsida. According to the characteristics of dwarf-shoots of reproductive organs, the pollen cones and ovulate cones of early conifers are structurally equivalent, which is consistent with the viewpoints of Hernandez-Castillo and Rothwell. According to the comprehensive analysis of plant fossils and sporopollen assemblages, the results show that Filices and Pteridospermopsida are dominant in flora, followed by conifers. Based on the comparison with the flora of the same period and the existence of the unique elements of the Cathaysia flora in the plant assemblage, it is confirmed that the flora has the features of middle-term Cathaysia flora, accompanied by the infiltration of the elements of Euramerican flora and Angara flora. It is speculated that the geological age of the study area should belong to the Artinskian kunguran period in the middle and late Cisuralian. The analysis of paleoenvironment shows that the cuticle characteristics of a large number of Filices and Pteridospermopsida have the same characteristics, that is, the vegetative leaves are all in the whole, the upper epidermis is thicker than the lower epidermis, and the stomatal apparatus is not obviously sunken, indicating that these plants are all growing in the humid climate environment. The characteristics of trichomes on the cuticle of a new species of Taeniopteris and reproductive organs of some conifers indicate that the plants in this period have the structural functions of preventing water evaporation and protecting reproductive organs, and this structure indicates that the plant fossils are parautochthonous burial. In addition, the true Filices and Pteridospermopsida, which are dominant in the flora, live in the humid environment of the hot temperate zone. The other components, such as Lycophyta, Sphenopsida, Noeggerathiales, belong to the plants that like to wet and distribute on the edge of the water body. Only conifers belong to the drought resistant plants and distribute on the outer edge. Therefore, according to the comprehensive characteristics of flora combination and the results of cuticle analysis, it is speculated that Yongchang flora in the middle and late Cisuralian lived in the plain lowland swamp environment, with the characteristics of warm and humid climate with seasonal drought.
Pages384
URL查看原文
Language中文
Document Type学位论文
Identifierhttps://ir.lzu.edu.cn/handle/262010/467028
Collection地质科学与矿产资源学院
Affiliation地质科学与矿产资源学院
First Author AffilicationSchool of Earth Sciences
Recommended Citation
GB/T 7714
王雪莲. 甘肃永昌山西组植物化石微细构造及孢粉学研究[D]. 兰州. 兰州大学,2020.
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