【作者】 李莎；

【导师】 万晓樵；

【作者基本信息】 中国地质大学(北京) ， 古生物学与地层学， 2012， 硕士

【摘要】 松辽盆地是晚白垩世亚洲古陆上面积最大的陆相淡水盆地之一，连续的湖相沉积为我们对大陆古环境和古气候的重建提供了良好的材料。盆地内部沉积岩系主要由碎屑岩组成，沉积物内包含了大量轮藻、腹足类、双壳类、介形类及脊椎动物化石。本文的研究材料来源于松辽盆地“松科1井（北孔）”的轮藻化石。轮藻化石从下向上连续分布，共鉴定出27属52种（包括6个未定种）。在四方台组和明水组建立了四个化石组合，由下至上是：Atopochara ulanensis-Hornicharaanguangensis， Atopochara ulanensis-Raskyaechara gobica， Hornicharaprolixa-Gobichara deserta和Grovesichara changzhouensis-Neochara sinuolata化石组合。本文将“松科1井（北孔）”的轮藻化石与同一时期的中国华北地区、华南地区，欧洲和南美等地做了对比，发现中国华南地区与欧洲、南美的轮藻分布较为相似，而松辽盆地的轮藻分布则与中国的华北地区和蒙古的戈壁盆地更为相似，具有标准化石意义的奇异轮藻亚科的晚期分子Atopochara ulanensis目前在全球仅发现于松辽盆地和蒙古戈壁盆地。根据轮藻化石及古地磁的证据，前三个化石组合年代为mid-Campanian至Maastrichtian期。第四个化石组合化石个体明显增大，顶部梅花形顶盖发育，侧壁具波状起伏，体现了一个完全不同于中生代面貌的生物群，其时代很有可能为古新世。因此，白垩系/古近系界线可能位于明水组二段上部。同时在明水组二段上部3个层位，我们还发现了发现9枚Ilyocyprissp.介形虫化石，似乎也预示着古新世的到来。我们还尝试性的进行了轮藻碳氧稳定同位素的测试。基于前人的研究，我们得知轮藻“茎部”钙化过程的同位素分馏过程是不平衡的，而藏卵器的氧同位素分馏过程是平衡的或接近平衡的，因此我们可以根据轮藻氧同位素所提供的信息重建古环境。更多还原

【Abstract】 Songliao Basin is one of the biggest lacustrine systems in Asia during Cretaceoustime. Well-preserved Cretaceous lacustrine deposits provide us with unique materialto study the paleoenvironment and paleoclimate of this period. Widespread deposits inthe basin are mainly composed of clastic sediments which contain abundant fossilsincluding charophytes, gastropods, bivalves, ostracods and vertebrates.The drilling program (SK1) has yielded2485.89m of continuous cores (96.46%recovery) and provides significant charophytes material for Cretaceous research. Thefossil record of Charophyta revealed in this study includes46organ-species and6indeterminate organ-species in27genera. After detailed biostratigraphic study ofcharophytes,4assemblages have been recognized in Sifangtai and MingshuiFormations: Atopochara ulanensis-Hornichara anguangensis assemblage,Atopochara ulanensis-Raskyaechara gobica assemblage, Hornicharaprolixa-Gobichara desert assemblage and Grovesichara changzhouensis-Neocharasinuolata assemblage. Based on charophyte assemblages, the Sifangtai Formation islimited to middle Campanian; and the Mingshui Formation is late Campanian toMaastrichtian in age. The appearance of gyrogonites from the4th assemblage isdifferent from others, which is characterized by its larger size, curved ornamentationson cellular spirals and apical rosette. It is likely that the upper part of the MingshuiFormation belongs to Paleocene, the K/Pg boundary is, therefore, within the upperpart of the Mingshui Formation. What’s more, we have discovered a new specie ofostracoda, Ilyocypris sp., which is of great significance.The study of stable C and O isotopes in lacustrine carbonates has led to insightsinto past climates. And we have collected some ostracodes and charophytes fossils tostudy for stable isotopes. Some experts have proved that the oxygen isotope ofcharophyte gerogonites is in equilibrium with that of water in which they live in for agiven temperature. Therefore, we can use them to elucidate the geochemistry of theancient water body in which they lived.更多还原