中国吉林东南部热河生物群的发现及植物化石研究

发布时间：2018-07-08 18:10

本文选题：吉林白山 + 早白垩世　；参考：《吉林大学》2016年博士论文

【摘要】：吉林省东南部白山市东北部发育一个小型北东向陆相沉积盆地,即白山盆地(原称浑江盆地)。盆地内地层自下而上为鹰嘴砬子组、林子头组和石人组,前两组地质时代曾被归于晚侏罗世,后者被划归晚侏罗世-早白垩世。除了前人少量化石名单外,盆地内尚未开展过系统的古生物学研究。本文重点对盆地内鹰嘴砬子组开展了古生物学研究。结果表明鹰嘴砬子组产丰富的动物、植物化石。无脊椎动物和脊椎动物化石主要类群有陆生软体动物腹足类、双壳类;节肢动物介甲类、介形类、昆虫类;脊索动物鱼类,两栖类等。代表性生物组合为Eosestheria-Ephemeropsis trisetalis-Lycoptera(EEL),与冀北-辽西地区义县组热河生物群一致,地质时代应划归早白垩世,而非前人的晚侏罗世。确认了白山盆地鹰嘴砬子组是热河生物群在吉林省东南部的赋存层位和中国境内最东部的分布区。白山盆地热河生物群中植物化石也较丰富,多为压型化石,是本文研究的重点。通过植物形态和表皮构造综合研究,确定该植物群由27属46种组成,以真蕨类和裸子植物为主,包括楔叶纲植物2属3种(6.52%)、真蕨纲植物3属4种(8.70%)、苏铁纲植物1属1种(2.17%)、银杏纲植物4属5种(10.87%)、茨康类植物5属12种(26.09%)、松柏纲植物8属14种(30.43%)、买麻藤纲植物2属2种(4.35%),裸子植物花果及种子化石2属5种(10.87%)。植物群落分析表明,当前植物群与辽西北票早白垩世义县组植物群在时空上可能具有一致性。从古生态学角度分析当前生物群,认为白山盆地热河生物群代表了一个早白垩世陆地生态系统。由淡水无脊椎动物介甲类、介形类、水生昆虫类、腹足类、双壳类、鱼类、两栖纲构成的淡水水域群落,以楔叶类为主构成的岸边-湿地群落,以真蕨类与苏铁类占优势的低地群落,以银杏类和茨康类为优势的山区坡地群落和以抗旱耐寒的松柏类为主的山区高地群落组成。从古环境气候角度分析当前生物群,认为该区季节性降水变化明显,多雨季节气候温暖潮湿,植被繁茂,昆虫等动物得以繁衍生息。少雨季节或干旱年份气候略干旱,少量喜旱生植物得以生存。从古植物区系划分角度分析,认为当前植物群位于早白垩世西伯利亚-加拿大植物区或中国北方植物区内,是暖温带-温带植物区系的重要组成部分。本文首次在吉林东南部白山盆地鹰嘴砬子组确认了早白垩世热河生物群的存在,化石代表了中国最东部的热河生物类群。同时,白山盆地作为热河生物群的第二个化石产地,对热河生物群的生态系统重建和古气候、古植物地理分析,了解热河生物群的生活环境,地貌特征、生物群落演替等都提供了有参考价值的新材料。
[Abstract]:A small north-east continental sedimentary basin, Baishan basin (formerly called Hunjiang basin), developed in the northeast of Baishan City, southeast Jilin Province. The inland strata of the basin are Yingzilazi formation, Linzitou formation and Shiren formation from the bottom to the top. The first two formations were attributed to the late Jurassic and the latter to the late Jurassic to the early Cretaceous. No systematic paleontology studies have been carried out in the basin except for a few fossil lists. This paper focuses on paleontology of the Yingzuilazi formation in the basin. The results show that there are abundant fossils of animals and plants in the Yingweilazi formation. The main groups of invertebrate and vertebrate fossils are terrestrial mollusk gastropods bivalves; arthropods ostracods insects; chordate fish amphibians and so on. The representative bioassemblage is Eosestheria-Ephemeropsis trisetalis-Lycoptera (EEL), which is consistent with the Gehe biota of Yixian formation in northern Hebei and western Liaoning. The geological age should be classified as early Cretaceous, rather than the late Jurassic. It is confirmed that the Yingzuilazi formation in Baishan Basin is the occurrence horizon of the Jehol biota in the southeast of Jilin Province and the easternmost distribution area in China. The plant fossils in the Gehe biota in Baishan Basin are abundant, and most of them are autoclastic fossils, which is the focus of this paper. Based on a comprehensive study of plant morphology and epidermis structure, it was determined that the flora was composed of 27 genera and 46 species, mainly composed of pteridophytes and gymnosperms. It includes 2 genera, 3 species (6.52%), 3 genera (8.70%), 1 genus (2.17%), 4 genera (10.87%), 5 genera (26.09%), 12 genera (26.09%), 8 genera (30.43%) and 2 genera (2 genera), respectively. 2 species (4.35%) and 5 species (10.87%) belonging to 2 genera and 2 genera of gymnosperms. The plant community analysis shows that the present flora may be consistent with that of Yixian formation in early Cretaceous. Based on the analysis of current biota from the perspective of paleoecology, it is considered that the biota of the Baishan basin represents an early Cretaceous terrestrial ecosystem. A freshwater water community consisting of freshwater invertebrates, ostracods, aquatic insects, gastropods, bivalves, fish and amphibians, and a shoreline wetland community dominated by cuneiformes. The lowland communities dominated by true ferns and cycads, the mountain slope communities dominated by ginkgo and Zikang, and the mountain highland communities dominated by drought resistant and cold tolerant pine and cypress. From the point of view of paleoclimate, it is concluded that the seasonal precipitation in this area is obvious, the rainy season is warm and humid, the vegetation is luxuriant, and the insects and other animals are able to reproduce. The climate is slightly dry in rainy season or dry year, and a small number of xerophytes are able to survive. From the point of view of the division of paleoflora, it is considered that the current flora is located in the early Cretaceous Siberia-Canada plant region or in the northern part of China, and is an important part of the warm temperate flora. In this paper, the existence of early Cretaceous Gehe biota has been confirmed for the first time in Yingzuilazi formation of Baishan basin in southeastern Jilin Province. The fossil represents the most eastern Jehol biota in China. At the same time, the Baishan basin, as the second fossil origin of the Jehol biota, analyses the ecosystem reconstruction, paleoclimate and paleogeography of the Jehol biota, and understands the living environment and geomorphological characteristics of the Jehol biota. The succession of biota and so on has provided a new material with reference value.
【学位授予单位】：吉林大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：Q911

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