【作者】 蒙丽；

【导师】 张建平；

【作者基本信息】 中国地质大学（北京） ， 古生物学与地层学， 2009， 硕士

【摘要】 以四川汉源地区大树镇摆鱼村湖相沉积剖面为研究对象,通过岩石地层学、地貌学、沉积学方法,结合野外记录,将剖面大致分为8个沉积阶段,3个旋回期,建立了大树摆鱼剖面沉积地层序列。通过粒度特征分析得出中值粒径平均为18.12μm,大都是粘土、粉砂、细砂互层。成层性和分选性较好,频率曲线呈明显的双峰特征,几乎没有粗尾;通过与岱海、西峰黄土、宣城河流沉积物的粒度分布及粒度参数特征对比,发现与岱海湖泊沉积基本一致,而与黄土及河流相沉积明显不同,判别出沉积物的成因类型与沉积环境,即大树摆鱼剖面主体是半深湖—深湖相湖泊沉积,部分是滨浅湖相湖泊沉积。通过高精度年代地层学和沉积学研究分析,大树摆鱼剖面基本能达到1cm/100a的分辨率。沉积时间约为206.74～80.55 KaBP,形成时代为中更新世晚期～晚更新世中期。通过内插和外推建立了大树摆鱼剖面高分辨率年代地层序列。大树摆鱼剖面中值粒度与磁化率呈正相关,与色度L呈负相关。高中值粒度和磁化率值、低L值指示了降水较多的暖湿气候环境;低中值粒度和磁化率值、高L值指示了降水较少的暖干或凉干气候环境。汉源地区200～80 KaBP的古气候演化过程分为3个时期8个阶段:(1)倒数第二间冰期末期(206.74～190.32 ka BP)以温暖而干旱气候环境为主;(2)倒数第二冰期(190.32～133.00 KaBP),以温凉较湿的气候环境为主,间夹一凉偏干时期;(3)末次间冰期(133.00～80.55 ka BP)以暖湿和暖干大幅波动气候环境为主,并以暖湿气候占主导地位。汉源地区的降水主要受控于太阳辐射影响下的印度季风强度的变化。而对于温度的变化,则与全球气候变化相一致。但汉源地区的环境指标记录与它们并不完全同步或一致,反映了区域性气候环境特征。更多还原

【Abstract】 Based on the lithostratigraphic and geomorphology, sedimentlogy methods, this paper deals with the lacustrine deposits from the section in Baiyu village Dashu town of Hanyuan, Sichuan province. This section could be divided into eight depositional stages, including the three climatic cycles, so the depositional sequence of the Dashu—Baiyu section has been established.According to the grain-size frequency distribution analysis, the Dashu—Baiyu section is composed of clay, silt and fine sand, the median size value is 18.12μm. The grain-size frequency curves show the bimodal feature without coarse tail; compared with the grain-size characteristics and parameters of Daihai lake sediments, Xifeng loess and Xuancheng fluvial deposits, the depositional features in Dashu—Baiyu section are essentially similar to Daihai lake, but different from the other two sites, so the Dashu—Baiyu section was deposited in a lake environment.Through the high-resolution chronostratigraphic and depositional analysis, the resolution in the Dashu—Baiyu section could basically reach 1cm/100a. Deposition period is from 206.74 KaBP to 80.55 KaBP, i.e., from the late Middle Pleistocene to middle Late Pleistocene. Based on the interpolation and extrapolation methods, the high-resolution chronostratigraphic sequence is set up in the Dashu—Baiyu section.The median grain size value and magnetic susceptibility in the Dashu-Baiyu section show a positive correlation, but a negative correlation with the color L. The higher median grain-size value, magnetic susceptibility value and lower L value indicate a warm-humid climate with rich precipitation; the lower median grain size value and magnetic susceptibility, higher L values indicate a warm or cold dry climate with fewer precipitation.Within the period from 200 KaBP to 80KaBP, the paleoclimate in Hanyuan, Sichuan could be divided into three periods and eight stages: (1) the terminal period of the last but one interglacial Age (206.74 ~ 190.32 ka BP),dominated by warm, arid climate; (2) the last but one Ice Age (190.32 ~ 133.00 KaBP), dominated by warm-cold, humid climate, intercalated with a cold drier period; (3) the terminal interglacial age (133.00 ~ 80.55 ka BP) ,characterized by the large-scale fluctuations between the warm humid climate and warm dry climate, dominated by the warm and wet climate.The precipitation in Hanyuan was mainly controlled by the change of the Indian monsoon intensity under the influence of solar radiation. As for the temperature change, it is identical to the global climate. But the depositional record in Hanyuan is not fully coincident with the global change, reflecting the special regional characteristics of climate and environment.更多还原