松科一井南孔白垩纪中期介形类化石壳体稳定同位素及微量元素研究

【作者】 王焯；

【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， 2010， 博士

【摘要】 本研究从中国大陆第一口以白垩系地层为主的全取心科学探井中获取了连续的、高分辨率的、较少受到后期破坏或影响的白垩纪陆相地层地质记录,用介形类化石壳体为材料,在生物鉴定分类基础上进行稳定同位素和微量元素的高精度测定,以期得到高分辨率的松辽盆地白垩纪中期古环境、古气候信息。本研究共采集岩心样品1003个,发现介形类化石557个,鉴定出15个化石组合带,测得252组碳氧同位素和189组微量元素比值数据。在分析整理、讨论后得出以下主要结论:1)松科一井南孔介形类化石壳体保存了长期的、连续的气候历史记录,展示了十分具有研究价值的碳氧稳定同位素序列和微量元素比值序列。作为大陆科学钻井,目前所得到的数据和各种资料有可能为中国甚至全球白垩纪同期陆相研究提供良好的稳定同位素序列标准。2)氧同位素数据在青山口组2、3段反映出最高的气候温度标志,自此后逐渐降温。这与同期海相研究认为的气候趋势变化相一致。同时,氧同位素还受到水体化学成分的影响。3)碳同位素数据揭示了至少5次正偏移地质事件和一个剧烈的负偏移地质事件。其中最大的负偏移事件反映了在松辽古湖盆演化过程中,因为湖泊萎缩,湖平面骤降,湖内生物大量灭绝,有机碳埋藏量相对减少,氧化量增加,导致大量的12C迅速溶解于水体中,水体沉积的碳酸盐δ13C在短期内急剧下降。4)Sr/Ca与Mg/Ca比值受到盐度、温度和沉积矿物的共同控制。能反映出青山口组2、3段盐度由低升高,再降低的过程;姚家组盐度整体低于青山口组3段,其中,姚家组1、2盐度的相对稳定,姚家组3段盐度又逐步增高;嫩江组1段和2段之间出现比值最低的区域,并且变化突然、迅速,推测可能受到降温的影响,并可能与氧化-还原环境、pH值改变和沉积中的碳酸盐沉积成分变化有关。5)将介形类化石壳体地球化学测验数据进行傅里叶变换,由所呈现的频谱图看出,所有数据中δ18O数据受周期性规律影响力最大,还原回原始δ18O序列,则说明它受到周期性气候影响最强烈。因此在同期各组数据中,相对而言,氧同位素是最好的古气候(古温度)指示剂。δ13C数据受到若干影响因子共同作用,其中有一个为主打影响因子,但影响力弱于温度对δ18O的作用。Sr/Ca、Mg/Ca比值则受到2到3个影响因子几乎等作用力影响。尤其是Mg/Ca比值,认为它受到至少温度、盐度和自生矿物的近等力共同作用。且由频谱图的幅值可以看出,仅盐度而言,对Sr/Ca的影响大于对Mg/Ca的影响。更多还原

【Abstract】 This paper from the Cretaceous Continental Scientific Drilling of China to obtain a continuous, high-resolution, less damaged by the Cretaceous continental strata , with ostracods fossil shells were used to experiment by stable isotopes and trace elements in high-precision determination based on identify the biological classification, in order to find high-resolution mid-Cretaceous paleoenvironment, paleoclimate information of Songliao Basin.In this study, 1003 core samples were collected, found 557 fossils of ostracods, identified the 15 fossil assemblage, the measured carbon and oxygen isotopes 252 ,and 189 trace element ratio data. Finishing in the analysis, discussion, draw the following conclusions:1)SK-1 by ostracods fossi shell preserved of long-term, continuous climate history, demonstrates very study value of carbon and oxygen stable isotopes and trace elements ratio sequence.That could provides a good sequence standards for China even global cretaceous continental research.2) The Oxygen isotope data in Qingshankou F.2,F.3 reflects the highest temperature sign here, and cooling since then. The Oxygen isotope records in Songliao basin seemingly track the corresponding contemporaneous isotopic marine records. At the same time, the oxygen isotopes was affect by chemical composition of water.3) Carbon isotope are revealed geological events at least five times . One of the biggest events in the negative shift reaction of Songliao Basin should affect by the lake shrink, then, the creature in lake mass extinction, organic carbon geobiology decrease relatively ,large increase 12C dissolved into the water,δ13C in the water in the short-term drop sharply finally.4)Temperature,salinity and mineral deposits are common control of Sr/Ca and Mg/Ca ratio. That reflect Qingshankou F. 2, 3 by low salinity increases, the reduction process, Yaojia F. salinity lower than whole Qingshankou F2、3. Yaojia F2 salinity relative stability. And gradually increased in Yaojia F3. Nenjiang F1、2 appeared the lowest data. That suddenly, rapid changes may be cooling effect, and may affect by oxidation-reduction environment, pH change and deposition of carbonate.5)Put the geochemical test data from ostracodes fossil shell to Fourier transform. The spectrum diagram from FFT shows that transformation parameters n will not change the spectral curve graphics changes in the large amplitude. Frequency corresponding changes may be due to excessive spacing samples and sampling not enough. Oxygen isotopes and carbon isotopebe are subjected to a periodic function, and the strong influence of oxygen isotopes influence than 10 times higher carbon isotopes. Various microelement by different laws on the cycle is weak, the common influence function alternately. Trace elements ratio spectrum diagrams clearly eliminate a lot of noise.更多还原