【作者】 姚菁；

【导师】 于洪军；

【作者基本信息】 中国科学院研究生院（海洋研究所） ， 海洋地质， 2014， 博士

【摘要】 第四纪冰期-间冰期交替的气候变化造成了全球海平面的波动，在海岸带地区表现为海陆交互相沉积。海岸带地区沉积物记录了沉积环境变化的丰富信息。通过研究海陆交互相沉积物来探讨沉积环境演化，重建区域环境变化历史，对于认识海陆相互作用以及预测未来环境演变具有重要意义。本文研究的LZ908孔位于渤海莱州湾南岸，在建立相对可靠的年龄框架的基础上，结合沉积物有孔虫特征研究了渤海南部地区海侵、海退的古海洋环境变化；对沉积物的颜色反射率各参数变化进行主成分分析，根据结果讨论影响海陆交互相沉积物颜色变化的主要因子；对沉积物粒度、颜色反射率、磁化率及孢粉这些指标进行分析，探讨各指标的环境指示意义、周期性变化及可能的影响因素。将各指标反映的气候变化与全球气候变化或海平面变化进行对比，得到莱州湾地区的区域性气候变化特征。得到的初步结论如下：1.通过对渤海莱州湾南岸LZ908孔的研究，识别了LZ908孔的有孔虫组合特征，结合AMS14C和光释光测年结果，对比渤海地区其它钻孔资料，对晚第四纪的环境变化过程进行了重建，认为三次大规模海侵开始于MIS7，MIS5和全新世，另外在MIS6的中期也发生了一次小规模的海侵。LZ908孔在MIS3阶段存在海侵地层，但是有孔虫特征显示这一时期的温度低于MIS5阶段。2.通过将LZ908孔的亮度与碳酸钙含量进行对比，发现L*值与CaCO3含量曲线的变化非常一致，在海陆交互相沉积物中，将L*值作为碳酸盐的替代指标是可行的。采用方差极大旋转法对样品颜色反射率的一阶导数进行了因子分析，通过将因子的载荷曲线与已知沉积物组分的一阶导数曲线进行对比，得到因子1与沉积物中有机物含量相关，因子2与沉积物中的粘土矿物含量关系较大，因子3与沉积物中针铁矿相关。3.通过对沉积物粒度的主成分分析，发现LZ908孔<32μm的细粒部分的含量与65oN夏季太阳辐射的变化和神农架三宝洞石笋的δ18O值的变化十分相似，表明LZ908钻孔沉积物<32μm的细粒部分的含量可以作为指示东亚季风强度的一个很好的指标。通过将磁化率和孢粉数据相结合，结果表明磁化率是一个良好的气候指标，高磁化率指示暖湿气候，低磁化率反映干冷气候。将LZ908孔的磁化率曲线与深海氧同位素曲线进行对比，磁化率高值对应氧同位素低值，为间冰期环境，磁化率低值对应氧同位素高值，为冰期环境。亮度值和CaCO3含量较高的层位大致为海平面较高的时期，指示温暖湿润的环境；相反地，亮度值和CaCO3含量较低的层位表明气候寒冷干燥，大多为海平面较低的时期。在LZ908钻孔的沉积序列中，红度值a*值的变化主要反映了沉积环境的氧化还原状态，冰期时期为低海平面时期的河漫滩环境，沉积环境为氧化环境，高价铁的氧化物和氢氧化物增加，沉积物颜色为红褐色或黄褐色，a*值也较大。间冰期的浅海或滨海环境，沉积环境为还原环境，高价铁的氧化物和氢氧化物转化为低价铁的氧化物和氢氧化物，沉积物颜色为深灰色、灰褐色或棕绿色，a*值也较小。4.通过对LZ908钻孔沉积物的粒度、磁化率和红度值a*值时间序列的频谱分析，得到250ka以来，渤海莱州湾南岸海陆交互相沉积物粒度、磁化率和红度值分别记录了轨道岁差、倾斜度和偏心率的周期特征。更多还原

【Abstract】 Quaternary glacial and interglacial climate change caused alternating fluctuationsin global sea level, and deposited transgressive and regressive interaction strata incoastal area. Coastal sedimentary environment changes frequently, so its sedimentrecords a wealth of information on these changes. Therefore, exploring the evolutionof the sedimentary environment of coastal areas, not only is important forreconstructing the history of regional environmental change and understandingland-sea interaction, but also can provide a scientific basis for predicting the futureevolution of the environment. LZ908core of this study is located in the Laizhou Bay,Bohai Sea, on the basis of relatively reliable age framework, we study transgression,regression changes of the ancient marine environment by sediment foraminiferacharacteristic in southern Bohai Sea; have principal component analysis about eachparameter change of sediment color reflectance, discuss the main factors affectingtransgressive and regressive sediments color change; analysis sediment grain size,color reflectivity, magnetic susceptibility and pollen indicators, to explore variousindicators environmental implications, cyclical changes and possible influencingfactors; contrast climate change indicated by these indicators with global climatechange or sea level changes, get regional climate variations in Laizhou Bay area.Preliminary conclusions are as follows:1. The foraminifera assemblages from a new borehole LZ908in the southerncoast of Laizhou Bay, Bohai Sea were studied, and then the transgressive strata wereindentified. Combined with accelerator mass spectrometry radiocarbon14C (AMS14C)and optically stimulated luminescence (OSL) ages, the occurrence time of thesetransgressions were re-determined. The result showed that three major large-scaletransgressions occurred separately at the beginning of marine isotopic stage7(MIS7), the last interglacial period (MIS5) and the Holocene. In addition, a small-scaletransgression occurred in the mid-MIS6, and the corresponding transgressive stratumwas deposited. The transgressive deposition of MIS3was also discovered in this study.However, the characteristics of the foraminifera indicated the environment during thisperiod was colder than that in the MIS5.2. By comparing the brightness and calcium carbonate content of LZ908core，found that the change of L*values and calcium carbonate content was very consistent,indicating a strong consistency between the two indicators, so the L*value used asalternative indicator of calcium carbonate content was feasible. Factor analysis on thefirst derivative of the color reflectance factor was conducted by great variance rotationmethod. By comparing factor load curve and the first derivative curve of thecomponent known to sediment, concluded that factor1associated with sedimentorganic content, factor2associated with clay mineral content of the sediments, andfactor3associated with the goethite content of the sediments.3. Through the principal component analysis of the sediment grain size, found<32μm fine fraction content of LZ908core changed similarly or basically consistentwith65o N summer solar radiation and δ18O value of Shennongjia Sambo CaveStalagmite. This showed that in the vast region of China, climate change wassynchronized, and <32μm fine fraction content of LZ908core could serve as a goodindication of the East Asian monsoon intensity index. By combining magneticsusceptibility and pollen data, the results showed that the magnetic susceptibility wasa good climate indicator, high susceptibility indicating warm and humid climate, lowmagnetic susceptibility reflecting dry and cold climate. Compared magneticsusceptibility curves of LZ908core with deep-sea oxygen isotope curve, highmagnetic susceptibility values corresponded to low oxygen isotopes, as interglacialenvironment, low magnetic susceptibility corresponding high oxygen isotope valuesfor the glacial environment. Brightness values and CaCO3content higher layersroughly corresponded to a period of high sea level, which indicating warm and humidenvironment. Conversely, lower brightness value and CaCO3content layers indicatedthat climate is cold and dry during low sea level period. In LZ908core sedimentary sequence, the red value a*mainly reflected oxidizing or deoxidizing state of thedepositional environment. Floodplain environment for the glacial period, lower sealevel and oxidizing condition, high iron oxides and hydroxides increased, sedimentcolor is reddish-brown or brown, a*value is larger. Between shallow or coastalenvironment, interglacial sedimentary environment is deoxidizing environment, highiron oxides and hydroxides turn into low iron oxides and hydroxides, sediment coloris dark gray, taupe or brown-green, a*value is small.4. By analyzing sediment grain size, magnetic susceptibility and red values a*ofLZ908, these indicators demonstrated that the climate in the southern Bohai Searesponded to the orbital forcing at the precession, obliquity and eccentricity bandsrespectively.更多还原