辽河三角洲ZK2孔晚更新世以来的沉积记录及全新世海侵期古气候研究
发布时间：2018-09-18 16:47
【摘要】：辽河三角洲是我国四大河口三角洲之一,地跨中温带和暖温带,温带季风性气候,是气候变化敏感区。建立辽河三角洲晚更新世以来的地层格架和物源区划分,有助于深入认识晚更新世以来渤海的地质演化历史;重建辽河三角洲全新世海侵期古气候及气候事件的区域对比研究,可以能够更好地“以古论今”,为分析和预测未来气候环境变化提供科学依据。ZK2孔是辽河三角洲迄今岩芯长度较长(41.4m)、取芯完整(取芯率平均为90.22%)、研究程度较深的地质研究钻孔,其全新世海侵期沉积的地层厚度较大,地层连续完整、岩性均一、无缺失,是研究辽河三角洲地区全新世海侵期环境演变和气候变化不可多得的良好材料。本文在对ZK2孔沉积物的岩性、粒度、有孔虫丰度及分子标志物等资料的基础上,结合精确的测年数据、海面变化等资料,并与其它钻孔资料分析对比,构建了辽河三角洲晚更新世33kyrBP以来的地层年代框架,恢复了辽河三角洲的沉积环境变迁历史,并运用稀土元素地球化学方法分析了晚更新世以来ZK2孔沉积物物源区的划分及母岩组合;通过提取ZK2孔U3段沉积物地球化学元素、有机碳氮、孢粉及分子标志物等古气候代用指标,重建了辽河三角洲全新世海侵以来古气候的演变过程,并结合国内外其它典型区域古气候研究成果,对比探讨了辽河三角洲古气候变化对典型气候事件的响应。通过研究区ZK2孔岩芯剖面的沉积特征(岩性、粒度、微体古生物、BIT),结合该钻孔年代学资料及临近钻孔的研究成果,可将ZK2孔自下而上划分U1-U4四个沉积段,即U1陆相(河道相),U2陆相(河漫滩相),U3海相(全新世海侵)和U4陆相(上三角洲平原相),并将U3段海相沉积自下而上进一步详细划分为U31、U32、U33、U34、U35五个沉积层,分别对应了河口湾相-浅海相-前三角洲相-三角洲前缘相-下三角洲平原相(潮坪相)。其沉积物粒度、有孔虫及生物标志物BIT等指标在不同沉积环境中出现了较为明显的变化,且变化趋势相似,揭示了辽河三角洲晚更新世33kyr BP以来的海平面变化的沉积历史,其中U3段沉积物(15.75m-2.65m)沉积连续无缺失,地层完整,测年数据可靠,较完整地反映了辽河三角洲9100 cal yr BP以来全新世海侵期的沉积历史。ZK2孔沉积物REE组成垂向变化比较复杂,存在明显的阶段性。REE含量主要受控于母岩组成和化学风化作用,存在明显的粒级效应,Fe-Mn氧化物、TOC对稀土元素组成产生一定的影响,而重矿物对其影响不明显。REE分馏参数(La/Sm)UCC和(Gd/Yb)UCC能够消除沉积物粒度、TOC、Fe-Mn氧化物和化学风化作用的影响,与重矿物相关性也不明显,较好地保存了母岩的REE特征,是ZK2孔沉积物物源区分析的有效指标。分析结果表明:研究区晚更新世33ka以来23.75-41.4m段沉积物具有与现代周边多条河流母岩源区一致的特征;15.75-23.75m段沉积物的母岩组合与来自辽河、大辽河的物源区母岩组合比较接近;0-15.75段是全新世海侵期形成的沉积物,其物质来源比较稳定,与现代大辽河和大凌河的物源区母岩组合最接近。运用常微量元素地球化学指标、有机碳/总氮、孢粉组合和生物标志物GDGTs等不同的气候代用指标,逐一分析了ZK2孔U3段(2.65-15.75m)全新世海侵期各指标的垂向变化及环境意义,从中挑选了对于气候变化比较敏感的元素地球化学CIA指标和基于GDGTs的MAAT指标,重建了辽河三角洲全新世海侵期9100yr BP以来古气候的变化过程,研究表明其经历了全新世早期快速升温期、中全新世早期温暖湿润期、中全新世晚期寒冷干燥期和全新世晚期温凉干燥期四个阶段;在全新世气候演化过程中,在孔深14.2m、12.25m、10.65m、9.35m、8.15m和5.65m处存在6次明显的降温变干事件。通过与国内外已有研究成果的区域对比分析,发现辽河三角洲全新世以来古气候变化过程与国内外相关研究的气候变化吻合较好,只是在气候波动发生的年代、事件发生的强度上存在差异。各气候代用指标对比研究发现CIA指标和MAAT指标较敏感,可以作为重建古气候的敏感代用指标,而MAAT指标在中全新世前对气候的响应要好于CIA指标。
[Abstract]:The Liaohe Delta is one of the four major estuarine deltas in China. It spans the middle and warm temperate zones and has a temperate monsoon climate. It is sensitive to climate change. The regional comparative study of paleoclimate and climatic events during transgression can provide a scientific basis for the analysis and prediction of future climate and environmental changes. The sedimentary strata of the Holocene transgression period are thick, continuous and intact, with uniform lithology and no defect. It is a rare good material for studying the environmental evolution and climate change during the Holocene transgression period in the Liaohe River Delta area. The stratigraphic chronological framework of the Liaohe River Delta since 33 kyrBP in the Late Pleistocene has been constructed, and the history of sedimentary environment changes in the Liaohe River Delta has been restored. The provenance zones of pore ZK2 sediments since the Late Pleistocene have been analyzed by using REE geochemical methods. The paleoclimate evolution of Liaohe Delta since Holocene transgression was reconstructed by extracting the geochemical elements, organic carbon and nitrogen, sporopollen and molecular markers from the sediments of U3 member of hole ZK2. According to the sedimentary characteristics (lithology, grain size, micropaleontology, BIT) of the core section of hole ZK2 in the study area, and the geochronological data of the borehole and the research results of the adjacent boreholes, the four sedimentary sections of hole ZK2 can be divided from bottom to top, namely, U1 continental facies (channel facies), U2 continental facies (floodplain facies), U3 marine facies (Holocene). The marine sediments of U3 member are further divided into five sedimentary layers: U31, U32, U33, U34 and U35, which correspond to estuarine-shallow-sea facies-front Delta facies-front Delta facies-lower delta plain facies (tidal flat facies). There are obvious changes in different sedimentary environments, and the trend of change is similar. It reveals the sedimentary history of sea level changes in the Liaohe River Delta since 33 kyr BP in Late Pleistocene. The deposits of the U 3 member (15.75 m-2.65 m) are continuous and intact, the strata are complete, and the dating data are reliable, which reflects the 9100 cal yr BP in the Liaohe River Delta more completely. The REE content in the sediments of hole ZK2 is mainly controlled by the composition of parent rocks and chemical weathering, and has obvious grain size effect. Fe-Mn oxides and TOC have certain influence on the REE composition, while heavy minerals have no obvious effect on it. The fractionation parameters (La/Sm) UCC and (Gd/Yb) UCC can eliminate the grain size of sediments, and the influence of TOC, Fe-Mn oxides and chemical weathering is not obvious, and the REE characteristics of parent rocks are well preserved. The results show that the sedimentation of 23.75-41.4m section of sediments in the study area since 33 Ka of Late Pleistocene is an effective indicator for provenance analysis. The sediments in the 15.75-23.75 m section are similar to those in the Liaohe and Daliaohe provenances, and the 0-15.75 section is formed during the Holocene transgression, and the sediments in the 0-15.75 section are of stable material source, and are similar to those in the Daliaohe and Daling provenances. The vertical variations and environmental significance of the indicators of the Holocene transgression in the U3 segment of hole ZK2 (2.65-15.75 m) were analyzed by using the geochemical indices of the trace elements, organic carbon/total nitrogen, SPOROPOLLEN ASSEMBLAGES AND biomarkers GDGTs. The elements which are sensitive to climate change were selected. CIA index and MAAT index based on GDGTs have reconstructed the paleoclimate change process since the Holocene transgression of 9100yrBP in the Liaohe River Delta. The study shows that the Liaohe River Delta experienced four stages: the rapid warming period in the early Holocene, the warm and humid period in the early Miocene, the cold and dry period in the late Miocene and the warm and dry period in the late Holocene. In the process of climate evolution, there are six obvious cooling and changing events at the depth of 14.2m, 12.25m, 10.65m, 9.35m, 8.15m and 5.65m. By comparing with the existing research results at home and abroad, it is found that the paleoclimate change process of the Liaohe River Delta since Holocene is in good agreement with the climate change of the relevant research at home and abroad, but in the climate fluctuation. The results show that the CIA and MAAT indices are more sensitive than the CIA indices, and they can be used as sensitive proxy indices for reconstructing palaeoclimate, while the MAAT indices are better than the CIA indices before the Miocene.
【学位授予单位】：中国科学院研究生院(海洋研究所)
【学位级别】：博士
【学位授予年份】：2015
【分类号】：P534.631;P532
本文编号：2248521
[Abstract]:The Liaohe Delta is one of the four major estuarine deltas in China. It spans the middle and warm temperate zones and has a temperate monsoon climate. It is sensitive to climate change. The regional comparative study of paleoclimate and climatic events during transgression can provide a scientific basis for the analysis and prediction of future climate and environmental changes. The sedimentary strata of the Holocene transgression period are thick, continuous and intact, with uniform lithology and no defect. It is a rare good material for studying the environmental evolution and climate change during the Holocene transgression period in the Liaohe River Delta area. The stratigraphic chronological framework of the Liaohe River Delta since 33 kyrBP in the Late Pleistocene has been constructed, and the history of sedimentary environment changes in the Liaohe River Delta has been restored. The provenance zones of pore ZK2 sediments since the Late Pleistocene have been analyzed by using REE geochemical methods. The paleoclimate evolution of Liaohe Delta since Holocene transgression was reconstructed by extracting the geochemical elements, organic carbon and nitrogen, sporopollen and molecular markers from the sediments of U3 member of hole ZK2. According to the sedimentary characteristics (lithology, grain size, micropaleontology, BIT) of the core section of hole ZK2 in the study area, and the geochronological data of the borehole and the research results of the adjacent boreholes, the four sedimentary sections of hole ZK2 can be divided from bottom to top, namely, U1 continental facies (channel facies), U2 continental facies (floodplain facies), U3 marine facies (Holocene). The marine sediments of U3 member are further divided into five sedimentary layers: U31, U32, U33, U34 and U35, which correspond to estuarine-shallow-sea facies-front Delta facies-front Delta facies-lower delta plain facies (tidal flat facies). There are obvious changes in different sedimentary environments, and the trend of change is similar. It reveals the sedimentary history of sea level changes in the Liaohe River Delta since 33 kyr BP in Late Pleistocene. The deposits of the U 3 member (15.75 m-2.65 m) are continuous and intact, the strata are complete, and the dating data are reliable, which reflects the 9100 cal yr BP in the Liaohe River Delta more completely. The REE content in the sediments of hole ZK2 is mainly controlled by the composition of parent rocks and chemical weathering, and has obvious grain size effect. Fe-Mn oxides and TOC have certain influence on the REE composition, while heavy minerals have no obvious effect on it. The fractionation parameters (La/Sm) UCC and (Gd/Yb) UCC can eliminate the grain size of sediments, and the influence of TOC, Fe-Mn oxides and chemical weathering is not obvious, and the REE characteristics of parent rocks are well preserved. The results show that the sedimentation of 23.75-41.4m section of sediments in the study area since 33 Ka of Late Pleistocene is an effective indicator for provenance analysis. The sediments in the 15.75-23.75 m section are similar to those in the Liaohe and Daliaohe provenances, and the 0-15.75 section is formed during the Holocene transgression, and the sediments in the 0-15.75 section are of stable material source, and are similar to those in the Daliaohe and Daling provenances. The vertical variations and environmental significance of the indicators of the Holocene transgression in the U3 segment of hole ZK2 (2.65-15.75 m) were analyzed by using the geochemical indices of the trace elements, organic carbon/total nitrogen, SPOROPOLLEN ASSEMBLAGES AND biomarkers GDGTs. The elements which are sensitive to climate change were selected. CIA index and MAAT index based on GDGTs have reconstructed the paleoclimate change process since the Holocene transgression of 9100yrBP in the Liaohe River Delta. The study shows that the Liaohe River Delta experienced four stages: the rapid warming period in the early Holocene, the warm and humid period in the early Miocene, the cold and dry period in the late Miocene and the warm and dry period in the late Holocene. In the process of climate evolution, there are six obvious cooling and changing events at the depth of 14.2m, 12.25m, 10.65m, 9.35m, 8.15m and 5.65m. By comparing with the existing research results at home and abroad, it is found that the paleoclimate change process of the Liaohe River Delta since Holocene is in good agreement with the climate change of the relevant research at home and abroad, but in the climate fluctuation. The results show that the CIA and MAAT indices are more sensitive than the CIA indices, and they can be used as sensitive proxy indices for reconstructing palaeoclimate, while the MAAT indices are better than the CIA indices before the Miocene.
【学位授予单位】：中国科学院研究生院(海洋研究所)
【学位级别】：博士
【学位授予年份】：2015
【分类号】：P534.631;P532
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