【作者】 席党鹏；

【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， 2008， 硕士

【摘要】 松辽盆地在嫩江早期发生了最大湖侵事件,在整个盆地范围内形成了一套黑色泥页岩夹油页岩。本次研究根据吉林德惠地区姚家车站剖面,以及农安地区的嫩江组一段上部—二段下部的后金沟剖面,通过系统采样,进行了深入的微体古生物学和地球化学研究。根据野外岩石地层特征及所含化石组合,将姚家车站剖面的地层厘定为姚家组三段上部和嫩江组一段下部,后金沟剖面地层厘定为嫩江组一段上部至二段下部。新确定了姚家组/嫩江组界线,并在界线之上40cm处发现嫩江阶底界的标志性化石愈氏链叶肢Halysestheria yui (Chang)。根据介形虫古生态学、沉积学及地球化学的分析恢复了姚家组三段上部沉积期至嫩江早期的湖平面的变化曲线和古水文信息,在嫩江组一段下部和二段底部,湖水有两次明显的加深,代表两次大规模的湖侵,其中第二次规模更大一些,伴随着湖侵,介形虫也经历了一个消亡、复苏和辐射的过程。姚家组TOC含量很低,有机质来源主要为高等植物;嫩江组一段下部TOC含量比较高,有机质来源主要为藻类和部分高等植物;向上TOC含量又有所降低,高等植物的输入增加;至嫩江组二段底部,TOC的含量很高,有机质的主要来源为藻类和高等植物的混合。地球化学和古生物指标表明,在嫩江组二段沉积初期的最大湖侵期,目前虽然没有松辽盆地遭受大规模海水侵入的证据,但可能至少经受两次短暂而微弱的海水影响,在此环境背景下形成薄层的油页岩。油页岩形成可能跟海水的影响可能导致盐度分层有关。此外,介形虫壳体的氧碳同位素研究表明,从青山口组二段下部沉积期到嫩江组一段上部沉积期,氧同位素平均下降2.98‰,碳同位素平均上升4.28‰,推测当时温度下降了大约10℃,气候由湿润变得相对干旱,湖泊生产力降低。更多还原

【Abstract】 In the early Nenjiang stage, a largest lake transgression occurred in the Songliao basin, depositing a group of black shale with intercalation of oil shale in the major areas of basin. Based on the detailed sampling from the Yaojiachezhan section in the Dehui region and Houjingou section in the Nong’an region, a further study of micropaleontology and geochemistry has been carried. The Yaojiachezhan section has been divided as upper Member 3 of the Yaojia Formation and lower Member 1 of the Nenjiang Formation, and the Houjingou section been divided as upper Member 1 and lower Member 2 of the Nenjiang Formation. The boundary between Yaojia and Nenjiang formations has been located. The first appearance of Halysestheria yui (Chang) was considered as the datum of bottom of Nenjiang stage, but it has been found to occur 40 cm above the boundary by the present work.Based on the ecology of ostracodes, sedimentary and geochemical analysis, the changes of the lake level and paleohydrology have been recovered. The lake level rised guickly at the sedmentary period of lower Member 1 of the Nenjiang Formation and lowemost Member 2 of the Nenjiang Formation respectively. The latter was larger. Along with the lake level rising, the ostracodes underwent a progress of species disappearance, recovery and radiation. In the upper Yaojia Formation, TOC is lower, organic matter was mainly origined from terrestrial plant; in the lower Member 1 of the Nenjiang Formation, TOC is relative high, organic matter was mainly origined from alga, as well as a few plant. Upward, the TOC decrease dramatically, and the origin of plant increased. In the lowermost Member 2 of the Nenjiang Formation, TOC is very high, and organic matter was mainly originated from the mixture of alga and plant. According to the analysis of Sr/Ba ratio, in conjunction with study of palaeontology, it is suggested that although the Songliao basin was not affected by large marine transgression, there were at least two short periods of seawater incursions, resulted in the deposition of thick oil shale. Based on the present study, the author refers a model to explain the oil shale formation, i.e. salinity stratification cased by the seawater intrusion.Oxygen and carbon isotope study of Cretaceous ostracodes has been carried. Oxygen isotopes show a ~10℃decrease in temperature from the sedimentary period of lower Member 2 of the Qingshankou Formation to upper Member 1 of the Nenjiang Formation. Carbon isotoperecords imply a biologically productive lake in the sedimentary period of lower Member 2 of the Qingshankou and less productive in the period of upper Member 1 of the Nenjiang Formation.更多还原