长江三角洲地区上新世以来主要气候转型事件的沉积响应研究

发布时间：2018-04-23 17:05

  本文选题：长江三角洲 + 上新世　； 参考：《中国地质大学》2017年博士论文

【摘要】：长江三角洲地区地质环境条件比较脆弱,松散层中孔隙水发育,软土层广布。充分认识上述与国民经济建设密切相关的地质条件,脱离不了中国东部,乃至全球新生代以来气候演化的框架认识。上新世以来,现长江河口地区堆积了近500 m的松散沉积。在这一较厚的松散层中,沉积环境的改变和演化不是偶然的,而是气候等因素作用下的必然现象。然而受制于测年手段、沉积环境变化复杂等因素的影响,对长时间尺度内的气候事件及其对区域、全球气候变化的响应研究比较薄弱、争论较大。因此,本文针对长江口横沙岛松散层厚395.4 m的LZK1孔开展了古气候演化沉积响应的综合研究工作。本次针对磁化率、粒度等传统指标进行了较高密度的采样,并引入了粒径—标准偏差、粒度端元组分模拟、轨道调谐、数字滤波、R/S分析、功率谱和小波分析等线性、非线性的数学处理方法开展了尝试研究,建立了天文年代标尺,综合对比了气候事件的沉积记录,并初步进行了气候周期变化研究,分析了沉积环境与气候之间的耦合关系。结果显示,相关方法在具有短时间尺度沉积缺失的持续沉降地区具有适应性,并能取得比较有效的成果。本次主要成果和认识有:1、沉积旋回清楚,沉积物特征复杂,沉积环境多样,沉积速率阶段性明显。研究剖面可划分为213个小层,15个大层。沉积物类型有粘土质粉砂、砂质粉砂、粉砂质砂、粘土—粉砂—砂、细砂、中砂、粗砂和含砾粗砂、砾质粗砂、砂质砾、泥质砂质砾等。上新世以来,先后发育了冲积扇、辫状河、曲流河、湖泊、曲流河、湖泊—河口湾、曲流河、河口湾、浅海、三角洲等多个沉积体系。沉积速率变化呈现明显的阶段性。晚更新世以来沉积速率较高,晚全新世达到最大,平均可达4.1~8.5 m/ka;晚更新世以前,平均沉积速率整体波动不大。在1076~1787 ka和5232~6033 ka间极低,约0.011 m/ka。2、质量磁化率、频率磁化率的粒度效应差别较大,气候指示意义不同。质量磁化率、频率磁化率总体上呈中等的负相关性,但局部层位无相关性,都以13~15 m、80~90 m、220~230 m、290~295 m为界发生四次显著变化,其中前三者与平均粒径、粒度组成含量的突变深度相一致。质量磁化率受粒度控制明显,多与250μm以下粒极正相关。频率磁化率除局部层位外,受粒度控制不明显。磁化率的气候指示意义不确定性较大,高磁化率可指示干冷气候,也可指示暖湿气候,而频率磁化率的气候意义较明确,高值指示暖湿气候,低值指示冷干气候。3、建立了剖面约6.3 Ma以来的年代标尺,识别了16次可能存在的极性漂移、亚时事件,且研究表明在有短时间沉积缺失的持续沉降区,可以通过轨道调谐方法建立总体可靠的年代框架。全新统、上更新统、中更新统、第四系和Gi/Ga界线、Gilbert底界分别约在41.6 m、107.1 m、143 m、219 m、296.6 m、369.6 m。可能记录了全新世I、全新世II、哥德堡、Mono lake、Laschamp、Blake、M/B Precursor、Kamicatsura、Santa Rosa、Jaramillo-cobb mountain、Olduvai、Feni-Reunion、Keana、Mammoth、sidufjall、Thvera等16个极性飘移和极性亚时事件。调谐后的频率磁化率在轨道周期上与ETP曲线高度相关,相关性超过了95%检验标准。100ka、41ka和23ka周期的带通滤波曲线与偏心率、斜率和岁差在振幅和相位上吻合较好,但局部时间段有差异,可能与低沉积速率、沉积速率突变或短时间尺度的地层缺失等因素有关。研究表明,在具有短暂沉积缺失的持续沉降区域,只要保证样品分辨率,可以通过轨道调谐方法建立可靠的年代框架4、通过粒径—标准偏差分析和端元组分模拟方法,提取了剖面的敏感粒径和端元组分,构建了两个组合端元组分分别作为夏季风和冬季风的替代指标。全剖面提取的敏感粒径和分段提取的敏感粒径差别较大,包含关系较差;但全剖面提取的端元组分与分段提取的端元组分基本相近,且能被后者包括。考虑粉尘堆积中悬浮组分通常的上限粒径,认为EM1(2.7~3.9μm)、EM2(10.8~14.3μm)、EM3(33.1~36.2μm)、EM4(76.7~83.9μm)四个端元组分直接或间接含有气候信息。以长期悬浮粉尘堆积的上限为界,构建了EM1+EM2、EM3+EM4两个组合端元,认为分别具有夏季风和冬季风气候演化指示意义,且与灵台黄土剖面平均粒径阶段具有明显可对比性。5、粒度端元组分、平均粒径、质量磁化率、频率磁化率的H值与区内现代气候指标值十分接近,可以很好地指示气候环境的变化。EM1+EM2粒度端元组分、平均粒径、质量磁化率、频率磁化率的H值较接近,且接近1。它们与现代夏季日照数、年最低日气温的H值相近,这表明其与夏季风的强弱密切相关。EM3+EM4粒度端元组分H值与其他四个差别较大,但大于0.5。与冬季平均气温、日照数基本相当,表明与冬季风的强弱密切相关。6、各类气候代用指标具有可比性,综合相关指标提出了上新世以来的气候框架,5.2 Ma、3.5 Ma、2.7 Ma、2.2 Ma、1.5 Ma、1.1 Ma、0.6 Ma等气候转化时间节点,与区域和全球尺度上的研究成果相一致。6.3~5.2 Ma,以暖湿气候为主,冬、夏季风作用均较强,但都逐渐减弱。5.2~3.5Ma间,仍以暖湿气候为主。以约4.7 Ma、4.2 Ma为界,夏季风呈减弱—增强—减弱的过程,而冬季风相对稳定。在约5.0 Ma同时发生冬、夏季风的强化事件。约3.5~2.7 Ma,气候较前一阶段明显变凉、变干,波动加大。夏季风轻微增强的同时,冬季风迅速增强并主导;但在3.0~3.1 Ma,冬、夏季风发生大幅波动。约2.7~2.2 Ma,冬、夏季风的同时显著加强,但冬季风仍占主导,气候变暖偏干。约2.2~1.5 Ma,气候仍较暖,但波动加大。夏季风总体稳定并略增强,冬季风较前明显减弱,两者呈反相关系。约1.5~1.1 Ma,气候较前阶段偏凉干,大幅波动。夏季风占主导,以1.2~1.3 Ma为界,由大幅波动转为逐渐减弱,与此同时,冬季风开始增强。约1.1~0.6 Ma,气候暖湿与干冷交替明显,波动进一步加大。夏季风继续减弱,而冬季风继续增强,两者呈继续反相关。约0.6~0.2 Ma,气候仍表现为暖湿与干冷交替的大幅波动,但总体呈暖湿特征。总体上,夏季风减弱,冬季风增强,两者呈反相关系。0.2 Ma以来,气候的暖湿与干冷交替波动加剧,冬、夏季风呈反相关系,表现为大幅度的增强(减弱),但夏季风总体上有所减弱,冬季风加强。MIS5期,气候暖湿,发育MIS5e、MIS5d、MIS5c三个阶段。MIS4期,气候变冷,MIS3期(本剖面仅保留48~29 ka阶段沉积),气侯略回暖,夏季风强度相对MIS4应变化不大,但波动明显,而这个阶段的气温转暖可能与冬季风的相对明显减弱有关。末次冰消期始于16 ka,在14 ka附近气候迅速转暖,可能指示B/A暖气的开始。全新世气候呈三分的特征,约11ka~5.5 ka间以夏季风占主导。约5.5~2.0 ka,气候明显变干。约2.0 ka以来,呈降温和变冷过程。7、初步的气候周期表明,不同指标记录的气候周期有一定差异,但总体都表现出了强烈的岁差和半岁差周期。周期数值波动性较大,具有一定规律性。频率磁化率、EM1+EM2粒度端元组分、Rb/Sr指标的频谱分析表明,区内气候周期主要呈准长偏心率(330 ka)、准200 ka(200 ka、250 ka、166-185ka)、准短偏心率(72~125 ka)、准斜率(38~50 ka和26~33 ka)、准岁差(16~23 ka)和半岁差(10~13 ka)等周期特征。除长周期外,其他周期都波动性较大,尤其是岁差周期,可能与沉积速率较小或短时间尺度的冲刷侵蚀等因素有关。600 ka、1100ka前后存在偏心率、斜率周期发育的区别,可能与中更新世气候革命有关。8、沉积环境变化与气候演化密切相关,清楚记录了区内在MIS5、MIS3、MIS1期间在气候控制作用下发生的三次海侵事件。气候转型阶段会缺失部分短时间尺度的沉积记录。
[Abstract]:The geological environment conditions in the Yangtze River Delta are relatively fragile, the pore water in the loose layer is developed and the soft soil layer is widely distributed. The geological conditions that are closely related to the national economic construction are fully understood, which can not be separated from the framework of the climate evolution in the eastern China and even the global Cenozoic era. Since the upper Miocene, the Yangtze River Estuary has accumulated nearly 500 m In this thicker loose layer, the change and evolution of the sedimentary environment is not accidental, but the inevitable phenomenon of climate and other factors. However, it is influenced by factors such as the means of dating, the complex environmental changes, and the response to the climate events in the long time scale and its response to the region and the global climate change. It is relatively weak and controversial. Therefore, this paper has carried out a comprehensive study on the paleoclimate evolution deposition response to the LZK1 hole of 395.4 m loose layer thickness in the Changjiang Estuary. This time, the traditional indexes such as magnetic susceptibility and grain size were sampled at a high density, and the particle size standard deviation, particle end tuple component simulation, orbit tuning, and numbers were introduced. The linear and nonlinear mathematical processing methods, such as filtering, R/S analysis, power spectrum and wavelet analysis, have been studied. The astronomical dating scales are established, the sedimentary records of climatic events are compared, and the climatic cycle changes are preliminarily studied and the coupling relationship between the sedimentary environment and the climate is analyzed. The results show that the related methods are related. The region with short time scale deposition loss is adaptive and can achieve more effective results. The main achievements and understanding are as follows: 1, the sedimentary cycle is clear, the sediment characteristics are complex, the sedimentary environment is diverse and the deposition rate is distinct. The research section can be divided into 213 small layers, 15 large layers. Sediment types have clay. Silty sand, sandy silt, silty sand, clay silty sand, fine sand, medium sand, coarse sand and gravel sand, gravel coarse sand, sandy gravel, and sandy gravel, and so on. Since Pliocene, the alluvial fan, braided river, meandering river, lake, lacustrine estuary, meandering river, estuarine, shallow sea, Delta and other depositional systems have been deposited. In late Pleistocene, the rate of deposition was higher, the maximum in the late Holocene, the maximum in the late Holocene, up to 4.1~8.5 m/ka, and the average fluctuation of the average deposition rate before the late Pleistocene. It was very low between 1076~1787 Ka and 5232~6033 Ka, about 0.011 m/ka.2, and the particle size effect of the mass magnetic susceptibility and frequency susceptibility was very different. The quality magnetic susceptibility and frequency susceptibility are generally negative correlation, but there are no correlation between the local layers and the four significant changes in 13~15 m, 80~90 m, 220~230 m and 290~295 m. The first three are in accordance with the average particle size and the depth of the grain size composition. Most of them are positively related to the particle size below 250 m. The frequency magnetization is not obviously controlled by the grain size except the local layer. The climatic indication of the magnetic susceptibility is uncertain. The high susceptibility can indicate the dry cold climate and the warm wet climate. The Climate Significance of the frequency magnetization is clearer, the high value indicates the warm wet climate, and the low value indicates the cold dry climate.3. The chronological ruler since about 6.3 Ma has been established to identify 16 possible polar drifting and subtemporal events, and the study shows that the overall and reliable age frame can be established through the orbit tuning method in the continuous subsidence area with short time deposition missing. Holocene, upper Pleistocene, Middle Pleistocene, Quaternary and Gi/Ga boundaries, and Gilbert bottom boundary 41.6 m, 107.1 m, 143 m, 219 m, 296.6 m, 369.6 M. may record the Holocene I, 16 Polar drift and polarity sub events such as the Holocene II, Mono lake, Laschamp, Blake. The magnetic susceptibility is highly related to the ETP curve on the orbit cycle, and the correlation exceeds the 95% test standard.100ka. The band pass filter curve of the 41ka and 23ka cycles is in good agreement with the eccentricity, the slope and the precession of the amplitude and phase, but there are differences in the local time period, which may be associated with the low deposition rate, the deposition rate mutation or the short time scale loss of the strata. The study shows that a reliable age frame 4 can be established by track tuning method in the persistent subsidence area with short deposition loss. The sensitivity particle size and end components of the section are extracted by the particle size standard deviation analysis and the end tuple component simulation method, and two combined end tuples are constructed. The sensitive particle diameter of the total section and the sensitive particle size of the segmented extraction are very different, and the inclusion relationship is poor, but the end tuples extracted from the whole section are almost similar to the end components extracted by the sections, and can be included in the latter. The four end tuples of EM1 (2.7~3.9 mu m), EM2 (10.8~14.3 mu m), EM3 (33.1~36.2 u m) and EM4 (76.7~83.9 micron) contain the climatic information directly or indirectly. With the limit of the long suspended dust accumulation, two combinatorial endpoints are constructed, and they are considered to have the significance of the climate evolution of the summer monsoon and the winter monsoon, respectively, and the loess section of Lingtai. The average particle size phase has obvious contrast.5. The H value of the grain end tuple, the average particle size, the mass susceptibility and the frequency susceptibility is very close to the modern climate index in the region. It can well indicate the changes in the.EM1+EM2 grain end components of the climate and environment, the average particle size, the mass susceptibility and the frequency susceptibility, and the connection of the H value of the frequency susceptibility. Nearly 1. of them are similar to the H value of the modern summer sunshine and the annual minimum daily temperature, which indicates that the H value of the.EM3+EM4 granularity end group is closely related to the intensity of the summer monsoon, but it is larger than the average temperature of 0.5. and winter, which is closely related to the strength and weakness of the winter wind, which is closely related to the.6 of the winter wind. The climatic framework since the Pliocene, 5.2 Ma, 3.5 Ma, 2.7 Ma, 2.2 Ma, 1.5 Ma, 1.1 Ma, 0.6 Ma and other climatic transformation time nodes, is proposed by the comprehensive correlation index, which is consistent with the regional and global scale research results.6.3~5.2 Ma, which is dominated by warm and wet climate, winter and summer wind are all stronger, but they are gradually weakened between.5.2~3.5Ma, still between.5.2~3.5Ma, still between.5.2~3.5Ma, still be weakened between.5.2~3.5Ma, still between.5.2~3.5Ma, still to weaken between.5.2~3.5Ma, still between The warm and wet climate is the main. With about 4.7 Ma and 4.2 Ma as the boundary, the summer wind is weakening - weakening process, and the winter wind is relatively stable. At about 5 Ma, the winter, the summer wind intensification event. About 3.5~2.7 Ma, the climate is obviously cooler, dry and fluctuant. The summer monsoon is slightly enhanced and the winter wind is rapidly enhanced and dominated. But in 3.0~3.1 Ma, winter, summer wind fluctuates significantly. About 2.7~2.2 Ma, winter and summer wind are significantly strengthened, but the winter wind still dominate, the climate warming is dry. The climate is still warmer, but the climate is still warmer, but the fluctuation increases. The summer wind is generally stable and slightly stronger, the winter wind is obviously weaker than before, and the relationship between the two is inverse relationship. About 1.5~1.1 Ma, climate is earlier than before. At the same time, the winter wind began to strengthen. At the same time, the winter wind began to strengthen. At the same time, the wind began to increase. About 1.1~0.6 Ma, the climate warm and dry cold alternated obviously, the fluctuation further increased. The summer wind continued to weaken, and the winter wind continued to strengthen, the two continued to reverse correlation. About 0.6~0.2 Ma, climate of about 0.6~0.2 Ma, climate. On the whole, the summer wind weakened and the winter wind was enhanced. Since the relationship between the two was.0.2 Ma, the climate warming and the dry and cold alternating fluctuation intensified, the winter and the summer wind showed a negative relationship, showing a significant increase (weakening), but the summer monsoon weakened in general. The wind strengthened.MIS5 period, climate warm and wet, developed MIS5e, MIS5d, MIS5c three stages,.MIS4 period, climate cold, MIS3 period (this section only retained 48~29 Ka stage deposition), gas slightly warm, the summer wind intensity relative MIS4 should not change little, but the fluctuation is obvious, and this stage of temperature warming may be relative to the relative decrease of winter wind. The period begins at 16 Ka and warm rapidly near 14 Ka, which may indicate the beginning of B/A heating. The Holocene climate is characteristic of three points, about 11ka~5.5 Ka is dominated by summer monsoon. About 5.5~2.0 Ka, the climate is obviously dry. Since about 2 Ka, the cooling and cooling process is in.7. The preliminary climatic cycle shows that the climatic cycles of different indexes are certain. The difference, but the whole show a strong precession and semi precession cycle. The cycle numerical volatility is larger, with a certain regularity. Frequency susceptibility, EM1+EM2 granularity end components, Rb/Sr index spectrum analysis shows that the climate cycle in the region is mainly quasi long eccentricity (330 KA), quasi 200 kA (200 kA, 250 Ka, 166-185ka), quasi short eccentricity (72~125). KA), the periodic characteristics of the quasi slope (38~50 Ka and 26~33 KA), the quasi precession (16~23 KA) and the semi precession (10~13 KA). Except for the long period, the other cycles are very volatile, especially the precession period, which may be related to the.600 Ka, which may be related to the less deposition rate or the short time scale erosion erosion. There is a difference between the eccentricity and the slope cycle development before and after the 1100ka. .8 may be related to the climate revolution of the Middle Pleistocene, and the sedimentary environment changes closely related to the climate evolution. It clearly records the three transgression events that occur during the climate control during the period of MIS5, MIS3 and MIS1 in the region.

【学位授予单位】：中国地质大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：P512.2;P532
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本文编号：1792846