【作者】 崔莹；

【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， 2007， 硕士

【摘要】 本研究对大庆油田徐22井青山口组/姚家组界线上下约12.20m的岩心做了详细采样、描述,进行了孢粉、介形类化石的分析、处理和鉴定,以及有机碳稳定同位素的测试和分析。该段岩心底部主要为灰黑色泥岩,水平层理发育,有丰富的孢粉和介形类化石;中下部主要为深灰绿色粉砂质泥岩,孢粉和介形类化石明显减少;中上部主要为灰绿色、浅灰绿色粉砂岩,层理不发育,化石很少;最顶部主要为褐红色粉砂岩、粉砂质泥岩,夹灰绿色粉砂岩。下部的孢粉化石属于Cyathidites- Balmeisporites-Cedripites组合,介形类化石属于Cypridea panda-Triangulicypris fusiformis组合,分布于青山口组三段。在1612.90m以上的层位中介形类化石Cypridea panda完全消失,以此作为青山口组/姚家组的界线,孢粉化石也在大致相同位置出现了姚一段组合Cyathidites-Schizaeoisporites组合,但孢粉数量极少。研究表明,在采样段底部沉积期主要为一种相对深水还原的沉积环境,介形类、水源和陆源生物均比较繁盛,孢粉Cyathidites类型占优势,显示出一种相对温暖湿润的气候;向上岩层颜色变浅,粒度有所加粗,化石含量迅速减少,反映出沉积水体急剧变浅,气候变得比较干热,不宜生物生存,在1612.90m界线处介形类化石完全消失,孢粉含量也急剧减少;再向上岩性明显变粗,并出现红层,反映当时湖水变得很浅,可能为三角洲淤积相,气候更加干热,并有波动,化石很少见。因此可以看出在界线上下热带、湿润—半湿润气候的大背景下,水体由深而平静变得浅而动荡,气候由相对温暖湿润变得相对干热,生物出现由繁盛到衰退的变化过程。有机碳稳定同位素显示出三个不同的演化阶段:在青山口组上部1618.50-1614.60m处,δ13C值总体偏负,最低为-27.9‰,最高为-23.5‰,平均为-25.4‰,反映出当时气候比较湿润,植被以C3植物为主,有机质来源以C3植物和水生浮游植物为主;界线附近(1614.60-1611.80m)处,δ13C值相对偏正且比较稳定,反映出当时气候开始变得相对干热,C4植物开始繁盛并占据优势;在姚家组下部(1611.80-1606.30m)处,δ13C值更加偏正且波动强烈,反映出当时气候更加干热,C4植物完全占优势,水源生物很少。上述研究结果和岩性、孢粉资料与松辽盆地其他地区的研究结果有很好的一致性。值得注意的是,在靠近界线1612.90m处,δ13C值发生正偏,峰值为-22.6‰,这与万晓樵等(2005)的研究结果一致,但幅度远不及后者大。研究还对古气候演化机制做了探讨,结果表明,在青山口组/姚家组界线附近为高温的热带气候,姚家组一段沉积期在有短暂回落之后,随后有所升高。同时,进一步的增温事件也使气候变得较干旱,且界线上下的干湿度变化要明显大于气温变化。关于详细的气候变化机制还将在今后通过更多方面的综合研究来探讨。更多还原

【Abstract】 Detailed sample collections and descriptions have been made from the upper Qingshankou to lower Yaojia formations in Xu-22 well of Daqing Oilfield. The length of sampled core is 12.20 meters. Careful identification and analysis on Sporopollen and Ostracods fossils have been carried out by present authors, and as well testing and analysis on Carbon stable isotope.At the bottom of this interval is the greyish-black mudstone in horizontal bedding. It riches in Sporopollen and Ostracods fossils. From lower to middle part is the dark grayish-green silt mudstone. The abundance of Sporopollen and Ostracods fossils reduces evidently. From middle to upper part is grayish-green and light grayish-green siltite, but beddings are obscure and fossils rare. The top part is brown-red siltite and silty mudstone within grayish-green siltite. The lower part yields Sporopollen assemblage of Cyathidites- Balmeisporites-Cedripites, and the Ostracod assemblage Cypridea panda-Triangulicypris fusiformis. They occur in the Third Member of Qingshankou Formation in Songliao basin. The upper part, just upon the boundary at 1612.90 meters, the Ostracods absolutely vanished. And a new Cyathidites-Schizaeoisporites Sporopollen assemblage appears. They are the indicators of First Member of Yaojia Formation. However the quantity is lower.Microbiota in the lower part of Qingshankou Formation imply a deepwater and disoxidation environment. There are large amount of Ostracods and other biota. The Sporopollen Cyathidites is dominant. This shows a warmer and moister climate. The color of upper layers turns light, the granularity increases and fossil abundance reduces rapidly. This shows that the lake became shallower, the climate was more dry and warm, and the creatures were hardly hitted. At the boundary of 1612.90m, Ostracods absolutely vanished, and Sporopollen reduce their number. Sediments in upper layers become coarse and in red color. This shows that the lake was much shallower, maybe in a delta silted phase. The climate is more dry and hot, and fluctuates frequently, and fossils are rare. Generally, at the boundary, the climateturned to more dry and hot from warmer and moister conditions, the water tended shallower and more fluctuant upwards, and as a result, biota reduces their abundance rapidly under the climate changes.Organic carbon stable isotope values show three evolvement stages. In the upper part of Qingshankou Formation,δ13C value shows a negative shift, with the lowest of -27.9‰, the highest on -23.5‰and average on -25.4‰. This reflects that climate was comparatively humid. C3 plant is dominant. C3 plant and water phytoplankton are the primary source of organic matter. At the boundary,δ13C values are comparatively stable. Comparatively dry and heat climate is reflected. C4 plant becomes to bloom and predominate. At the lower part of Yaojia Formation, a clear positive excursion ofδ13C value occurs. This reflects more dry and heat climate and C4 plant predominates absolutely. Few fossil has been found. Study results upon, lithologic characters and Sporopollen data are in accordance with the research in other parts of the Songliao besin.At the boundary,δ13C values show a positive shift. The highest value is -22.6‰. This result is in accordance with the research of Wan (2005). However its fluctuant range is much lower than the latter. This is remarkable.Moreover, we also probe into the evolutionary mechanism. The results indicate that high temperature tropic climate occurs during the boundary time. There is a little regression in the First Member of Yaojia Formation. Meanwhile, farther calefacient events make the climate more dry and heat. The change of humidity is evidently larger than the change of temperature.更多还原