【作者】 葛玉辉；

【导师】 孙春林；

【作者基本信息】 吉林大学 ， 古生物学与地层学， 2008， 博士

【摘要】 内蒙古石拐盆地位于我国北方中部,属东北地层区、阴山地层分区,是一个具有代表性的中生代断陷含煤沉积盆地,近东西方向,长约90km,宽约20km。地理坐标:N40°35′-40°45′,E109°45′-109°50′。盆地内地层主要由下侏罗统五当沟组、中侏罗统召沟组和长汉沟组、上侏罗统大青山组组成。作者对石拐盆地侏罗纪地层进行了野外地质调查,其中重点开展了对中侏罗统召沟组详细调查,测制了剖面,系统采集了丰富的植物化石,并对该组的岩性岩相特征进行了观察分析。盆地内召沟组岩性主要由砾岩、砂砾岩、含砾粗粒岩屑长石砂岩、薄层粉砂岩、炭质页岩和薄煤层组成,根据沉积特征和岩性特征可以划分为上下两段。下段为砂砾岩段,上段为含煤段,是召沟组主要含煤层。该组岩性、厚度在横向上变化较大,南翼地层较厚,北翼较薄,反映了召沟组沉积时期盆地地形北陡南缓的不对称的特点。细砂岩和粉砂岩中含丰富的植物化石。该组分别与下伏地层下侏罗统五当沟组和上覆地层中侏罗统长汉沟组为整合接触。通过野外地质调查,综合岩石地层特征分析,对召沟组地层进行了重新划分,将前人划归中侏罗统召沟组上段划归中侏罗统长汉沟组。召沟组岩性、岩相在纵向和横向上变化较大,纵向上下部以河流相为主,间夹有短暂的滨浅湖相沉积;上部为滨浅湖-泥炭沼泽相沉积。在横向上盆地南翼以粗粒碎屑为主的河流-湖泊、泥炭沼泽相,而北翼为钙质细碎屑岩和黑色页岩为主,夹煤线,总体反映浅湖-半深湖相特点。盆地内中侏罗统召沟组富含植物化石,经研究计有18属31种组成,分属于真蕨纲、苏铁钢、银杏纲、茨康纲、松柏纲和极少数分类位置不明分子Taeniopteris。该植物群的总体面貌是真蕨纲植物所占比例最高,茂盛的银杏目,茨康目和以针状叶为主的松柏纲也占有很大比例,而苏铁纲分子较少,主要为本内苏铁目和尼尔桑目,结合沉积特征分析,植物群的总体面貌反映了具有季节性变化的温暖湿润的温带-暖温带气候环境。代表一个温暖潮湿气候具有季节性变化环境下生长的植物群。根据植物群的组成特征和组成分子分析,当前植物群大致相当于李佩娟(1988)的饮马沟、大煤沟植物组合和周志炎(1995)提出的我国北方中侏罗世早期组合。通过与我国北方、俄罗斯西伯利亚、中亚、英国约克郡等地的一些中侏罗世植物群比较,反映植物群总体面貌,组成特征以及大多数属种与这些植物群近似,指示了与这些植物群是在相似环境下生长的大致同期的植物群。通过沉积学分析,石拐盆地中侏罗世早期(召沟组沉积时期)遍布河流、湖泊和泥炭沼泽,形成了多层、大规模的工业煤层,分布范围较广。代表了当时植物繁茂,气候环境有利于植被生长的温暖湿润的温带-暖温带气候环境。作者在广泛收集相关文献资料的基础上,阐述了银杏目和茨康目的地史、地理分布,回顾了银杏目、茨康目的起源和演化以及研究进展。重点对植物群中的银杏目、茨康目部分叶部化石角质层进行了分析,首次对该区的Ginkgo和Czekanowskia两个属的表皮构造进行了研究,描述建立了银杏目新类群1新种,石拐银杏Ginkgo shiguaiensis sp. nov.。茨康目新类群2新种,中华茨康叶Czekanowskia (Harrisalla) chinensis sp. nov.和石拐茨康叶Czekanowskia (Vachrameevia) shiguaiensis sp. nov.。作者通过对内蒙古石拐盆地中侏罗世植物群及相关地层研究,为进一步了解我国北方中侏罗世植物群特征,提高中侏罗世植物群研究水平,为开展相关地层对比工作增加了新资料。为深入开展植物区系研究,分析古地理、古气候环境提供了新证据。对在该区进一步寻找煤炭资源具有重要的参考价值。更多还原

【Abstract】 The Shiguai Basin, one of the well-know Mesozoic coal-bearing basins in northern China, is located in the central part of Inner Mongolia ( N40°35′-40°45′,E109°45′-109°50′). It is a typical small scale non-marine coal-bearing basin of Jurassic age and extends from east to west for about 90km long by 20km wide in the widest part. In this basin, the Jurassic sediments are well developed and especially well exposed at the Toudaogou-Erdaogou Section. The Jurassic deposits are divided into four formations in ascending order: the Lower Jurassic Wudanggou Formation, the Middle Jurassic Zhaogou Formation and Changhangou Formation, and the Upper Jurassic Daqingshan Formation. Specimens of fossil plants were collected from the Zhaogou Formation at the Toudaogou-Erdaogou section. Lithologically, the Zhaogou Formation can be subdivided into two members based on the field investigation made by the author. The lower member is represented by fluvial and swamp sediments consisting of conglomerates, sandstones, siltstones, shales and coal layers. Abundant fossil plants described in this paper were collected from the fine-graded sandstone bed from the lower part of this member. Some bivalves have been found in this member. The upper member is composed of sandstones, siltstones, shales and coal beds indicating lacustrine and swamp sediments. This member is mainly coal bearing deposits.To our knowledge, fossil plants from this basin have not been studied in detail. From 2004 to 2006, a lot of fossil plant specimens were collected from Zhaogou Formation by the author and his colleagues. The preliminary examination shows that this is a larger and diverse flora containing Filicopsida, Cycadopsida, Ginkgopsida, Czekanoskiopsida, Coniferopsida, and it is mainly dominance of the Filicopsida, Ginkgopsida, Czekanoskiopsida and Coniferopsida. Detailed studies on the fossil plant specimens reveal that the flora of the Zhaogou Formation are composed of 18 genera and 31 species, The list of the identified fossils is as follows:Filicopsida ( 3 genera and 10 species) Coniopteris burejensis(Zalessky)Seward Coniopteris hymenophylloides(Brongniart)Seward Coniopteris sp. Todites williamsoni(Brongniart)Seward Cladophlebis shansiensis Sze Cladophlebis hsiehiana Sze Cladophlebis argutula(Heer)Fontaine Cladophlebis angusta(Li)Wu comb.n. Cladophlebis haiburnensis(L.et H.)Brongn Cladophlebis sp.Cycadopsida(3 genera and 3 species) Pterophyllum baotoum Chang Anomozamites major (Brongniart) Nilssonia compta(Phillips)Ginkgopsida (2 genera and 4 species) Ginkgo shiguaiensis sp. nov. Gingko longifolius (Phillips) Harris Ginkgo sp. Baiera furcata (L. et H.) BraunCzekanoskiopsida (4 genera and 6 species) Czekanowskia (Harrisalla) chinensis sp. nov. Czekanowskia (Vachrameevia) shiguaiensis sp. nov. Phoenicopsis (Phoenicopsis) cf.angustifolia Heer Phoenicopsis speciosa Heer Sphenarion paucipartita (Nathorst) Harris Ixostrobus lepidus(Heer)HarrisConiferopsida(5 genera and 6 species) Pityophyllum lindstroemi Nath. Pityophyllum nordenskioldi Heer Storgaardia sp. Podozamites sp. Lindleycladus lanceolatus (L.et H.)Harris Elatocladus manchurica Yabe et OishiPlantae insertae sedis(1 genera and 2 species): Taeniopteris tenuinervis Braun Taeniopteris sp.The flora is characterized by prosporous and diverse Filicopsida, Ginkgopsida, Czekanoskiopsida and Coniferopsida. The occurence of Coniopteris burejensis, Coniopteris hymenophylloides marks the difference between the present flora and the Early Jurassic flora. The known species of Ginkgopsida formed during the Early Mesozoic with a relatively high variation have been identified in the flora. They are mostly the important element of the Early and Middle Jurassic in North China. The present elements of Coniferopsida are not quite different from those of the Early Jurassic. Cycadopsids with low variation are mostly the common species of the Middle Jurassic flora in North China, Central Asia and Siberia. All these mark the Early Assemblage of the Middle Jurassic and indicate the age of Middle Jurassic in North China. Fossil bivalves associated with the flora also support the Middle Jurassic age.The existence of the large amount of Filicopsida and the absence of the typical members of dipteridaceae and matoniaceae of the tropical and subtropical floras in the south China indicate the flora were under relatively warm and moisture climate; the high percentages of the Gingkgopsida, Czekanoskiopsida reveals a temperate seasonal climate relatively cool. The mass existence of Coniferopsida is also an indicator of temperate climate. Hence, the flora indicate climate of warm or slightly warm temperate-temperate zones with apparent season variations.Systematic comparison of the flora in the area with those of the same was made. The results showed that the flora is similar to those found in the Yinmagou Formation, Dameigou Formation of the Northeast Part of the Caidamu Basin in Qinghai, the Haifanggou Formation of West Liaoning Province, Mentougou Formation of Beijing, Yima Formation of West Henan, They might be under similar environments and probably form at the same period. Meanwhile, the present flora are quite similar to those of the Middle Jurassic in the central Asia and Siberia, especially some genera and species are same as those in the Yorkshire flora of the Middle Jurassic in England where some marine intercalations are found. This also supports the flora in the Zhaogou Formation are Middle Jurassic in age.For the first time, the study has conducted a detailed dissecting study on leaves as compression .The cuticle was first immersed in 40% HF solution for about 8-24 hours depending on the different degrees of carbonization. Then the cuticle was washed a few times using distilled water before transferring to the Schulze’s solution. When the color of the cuticle in the Schulze’s solution changes into light brown, the cuticle was washed using distilled water and then treated with 5% NH4OH. Wash with distilled water a few times before mounting on SEM stubs. SEM samples were air dried and coated with platinum. All samples were examined using a JSM-6700 scanning electron microscope at an acceleration voltage of 10kv. All specimens and preparations are stored in the Research Center of Paleontology and Stratigraphy of Jilin University, Changchun, China.By using scanning electron microscope. According to their leaf-shapes and well-preserved cuticulae, this thesis has carefully described the newly found Ginkgo shiguaiensis species, Czekanowskia (Harrisalla) chinensis sp.nov., and Czekanowskia (Vachrameevia) shiguaiensis sp.nov.. This thesis has also studied the structures of leaf-cuticulae of the two previously found Ginkgo longifolius and Ginkgo sp. in the study area. The appearance of these species in Middle Jurassic strata in Daqingshan area, Inner Mongolia is an important extension of Ginkgoales and Czekanowskiales in Northern Hemisphere strata and geographical distribution areas, which significantly improved the study level of the abovementioned two kinds of fossils.The thesis has systematically described Mesozoic Ginkgoales and Czekanowskiales fossils in northern China, reported their detailed classifications, and discussed classification principle,suborder and species. This study will play a positive role in enhancing the study level of Ginkgoales and Czekanowskiales of China, and provide new reference materials for studying middle Jurassic flora in Shiguai basin and other northern China areas, for contrasting of Coal-bearing strata, and for restoring palaeo-geography and palaeo-climate etc.更多还原