【作者】 陈晓辉；

【导师】 李铁刚； 张训华；

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

【摘要】 北黄海独特的地理位置、丰富的陆源物质供应量与多变的沉积环境使其开展晚第四纪以来沉积地层与古环境的研究具有鲜明的区域特色。北黄海晚第四纪以来地层格架及物源环境的研究，有助于深入认识晚第四纪以来中国东部陆架的地质演化史，丰富全球变化区域响应的认识，同时为揭示中小型河流及其影响下的近岸泥质区在陆架海陆相互作用中的意义，深入理解研究区海陆相互作用的机制提供科学依据。本论文利用北黄海中西部陆架采集的4916km高分辨率浅地层剖面的声学记录与北黄海目前最深、取芯最完整的DLC70-2孔沉积地层的对比分析，揭示了研究区晚第四纪（MIS6期）以来的地层框架，运用REE地球化学方法，结合DLC70-2孔及辽东半岛东南近岸泥质区3个柱状样的沉积特征的分析，揭示晚第四纪北黄海中西部陆架沉积物物源环境的演化及其对海平面变化的响应过程。浅地层剖面上自上而下识别出了研究区可连续或不连续追踪的10个声学地层界面（T0、T1、T2、T3、T4、T5、T6、T7、T8、T9），划定了介于上述界面之间具有层序意义的10个声学地层单元或亚单元（SU11、SU12、SU2、SU3、SU41、SU42、SU51、SU52、SU53、SU6）。DLC70-2孔（结合前人NYS-101/NYS-102孔）沉积特征与过孔浅地层剖面声学记录的对比分析显示，依据浅地层剖面进行的声学地层划分与钻孔岩心的沉积地层划分有良好的对应关系，自上而下划分出了研究区晚第四纪（MIS6期）以来与声学单元相对应10个沉积地层单元或亚单元（DU11、DU12、DU2、DU3、DU41、DU42、DU51、DU52、DU53、DU6）。北黄海中西部陆架晚第四纪（MIS6期）以来地层的发育及沉积环境的变化与海平面的波动密切相关。研究区MIS6期以来发育3次沉积旋回，大部分地层形成于MIS5期至MIS4期早期、MIS3期早中期、MIS1期早中期3组海平面相对较高时期，分别对应滨海-浅海相、滨海-河口湾相、滨海-浅海相沉积，内部地层相对连续，为海侵体系域与高水位体系域的沉积；而在MIS6期、MIS4期晚期、MIS2期3组海平面较低时期，分别发育河流-河口充填相、河口充填相、河口充填相及上覆河流泛滥平原相沉积，与下伏地层之间存在明显的沉积间断，为低水位体系域同期的沉积。DLC70-2孔沉积物REE组成垂向变化比较复杂，存在明显的阶段性。REE含量主要受控于源岩组成，存在明显的粒级效应，除此之外，Fe-Mn氧化物、化学风化作用对稀土元素组成产生一定的影响，而TOC及重矿物对其影响不明显。DLC70-2孔沉积物REE标准化配分模式及分馏参数判识图解显示，研究区MIS6期晚期（69.23-60.72m段）与MIS4期晚期（35.00-38.90m段）主要为鸭绿江及大洋河源；MIS5期早期（60.72-48.90m段）与MIS4期晚期以来（35.00-0m段）主要来源于黄河物质；而MIS6期中期（70.60-69.23m段）与MIS5期中晚期（38.90-48.90m段）主要受到黄河、鸭绿江及大洋河共同作用；长江与朝鲜半岛河流对研究区影响不明显。海平面的波动与黄河入海口的变化是研究区晚第四纪以来物源变化与物质供应量的主要控制因素。北黄海中部晚更新世末低海面时期发育的硬质粘土层形成年龄介于12602~10357cal yr BP之间，年代上与发生在12.9~11.6ka期间的末次冰消新仙女木气候回冷事件相吻合，与不同沉积环境中形成的北黄海泥炭层为同一时期的沉积，可作为新仙女木事件在北黄海陆架响应的一个重要证据。高含量淡水藻类（环纹藻、盘星藻）与香蒲的存在表明北黄海硬质粘土层的形成环境主要为淡水水域，而硬质粘土层中藜科－蒿属的存在指示其形成期间间或受到海水的影响，其上下层段海生沟鞭藻含量的增加说明硬质粘土层沉积初期及形成后期海水作用的增强，淡水藻类与陆生植物孢粉此消彼长的变化规律反映了硬质粘土层形成的阶段性特征。硬质粘土层中蒿属－香蒲－松－禾本科－单缝孢和松－蒿属－禾本科－单缝孢－香蒲孢粉组合表明研究区当时处于寒冷而湿润的环境，低地为以河流湿地为主的平原草甸，周边山地有针阔叶混交林分布。高分辨率浅地层剖面资料显示辽东半岛东南近岸海域沿岸分布着一泥质沉积体，剖面上呈现丘状、低倾角向海向陆双向进积，最厚处可达14m，向海向陆双向变薄至<2m，空间上位于大连湾东北和长山群岛西南部海域，延伸至距离鸭绿江河口180-300km，泥质沉积体分布区水深范围20-40m。该泥质沉积是全新世6.5ka BP高海面以来形成的高水位体系域的沉积，物源主要来自鸭绿江&大洋河物质。海洋动力环境(潮流、波浪、辽南沿岸流、黄海暖流等)是控制辽东半岛近岸海域沉积物再悬浮、运移与沉积的主要因素。辽东半岛东南近岸泥质沉积区末次冰盛期以来的古环境演化主要受控于海平面变化及物源供应，形成于10383-10396cal yr BP左右的泥炭层，与新仙女事件在北黄海响应的泥炭层为不同时期的沉积，主要为末次冰消以来融水脉冲事件（MWP-1B与MWP-1C）之间海平面相对停滞时期的产物。更多还原

【Abstract】 The North Yellow Sea (NYS) can be regarded as a typical key area for studyingsedimentary stratigraphy and paleoenvironment during the late Quaternary because of itsunique Geographic, geological, hydrologic bankgrounds. The research of sedimentarystratigraphic framework and environmental evolution in NYS during the late Quaternary notonly contributes to understanding the geological evolutionary history in the shelf area of theeastern China Seas and enriching the regional response theory to global change, but alsoprovides scientific evidences for revealing the significance of small-medium size rivers andcoastal mud areas to land-sea interaction at the marginal sea and understanding themechanism of land-sea interaction in the study area.In this paper, throuth a comparison between4916km high-resolution subbottomseismic profiles, and sedimentary characteristics of the core DLC70-2with the longest lengthand highest recovery rate by far in NYS, the stratigraphic framework in the study area sincethe late Quaternary (MIS6) will be precisely disclosed. In addition, by a geochemical analysisof rare earth element (REE), which will be compared with the sedimentary characteristics ofcore DLC70-2from the central of NYS and three piston cores in the Liaodong Peninsulasoutheast coastal mud area, the provenance environmental evolution in the midwest area ofNYS and their responses to the global sea-level fluctuations since the Late Quaternary will berevealed.High-resolution seismic profiles are divided into ten major regionally continuous todiscontinuous seismic bounding surfaces, which are designated T0、T1、T2、T3、T4、T5、T6、T7、T8、T9in descending stratigraphic order. Meanwhile, a total of ten seismic sequenceunits (SU11、SU12、SU2、SU3、SU41、SU42、SU51、SU52、SU53、SU6) are identified amongthe seismic surfaces. The contrastive analysis between sedimentary characteristics of coreDLC70-2(compared with previous cores NYS-101and NYS-102) and core-passing seismicprofile in NYS shows that stratigraphic units in the cores are confidently correlated withseismic units in the profiles, that is ten stratigraphic units (DU11、DU12、DU2、DU3、DU41、DU42、DU51、DU52、DU53、DU6) in the study area during late Quaternary correspond to tenseismic units (SU11、SU12、SU2、SU3、SU41、SU42、SU51、SU52、SU53、SU6), respectively.Strata formation and sedimentary sedimentary environment changes in the study area since MIS6are strongly controlled by sea-level fluctuations. There exists three majorsedimentary cycles. Most of the relative continuous successions were formed in threehighstand sea-level stages of MIS5to the early period of MIS4, the early-middle period ofMIS3and MIS1, which correspond to coastal-shallow sea facies, coastal-estuary facies,coastal-shallow sea facies respectively and regarded as Transgressive System Tract andHighstand System Tract. Major erosions and hiatuses happened in three lowstand sea-levelstages of MIS6, the late period of MIS4, MIS2, corresponding to fluvial-estuary filling facies,estuary filling facies, estuary filling and floodplains facies respectively and regarded as thesame period deposit with Lowstand System Tract.The vertical variations of REE compositions in core DLC70-2are relativelycomplicated and formed in different stages. The REE complication is mainly controlled bysource rocks and influenced by granularity. Furthermore, Fe-Mn oxides, Chemical Weatheringalso exert some influence on the REE composition. However, the effects of biogenouscarbonate and heavy minerals are not significant. The result of provenance discriminationexhibits that the sediments deposited at the stages of the late period of MIS6(69.23-60.72m)and the late period of MIS4(35.00-38.90m) are mainly derived from Yalu River and DayangRiver, the sediments at the stages of the late period of MIS5(60.72-48.90m) and since thelate period of MIS4(35.00-0m) mainly deriving from Yellow River, whereas the sediments atthe stages of the middle period of MIS6(70.60-69.23m) and the middle-late period of MIS5(38.90-48.90m) are jointly influenced by Yellow River, Yalu River and Dayang River, theeffects of Yangtze River and Korean Peninsula rivers being not clear. The sea-level fluctuationand estuary change of Yellow River are regarded as a dominated factor of provenancevariations and sedimentary fluxes in the study area since late Quaternary.AMS14C age data together with lithology analysis suggest that the hard clay in thecentral area of NYS was formed about12563to10330cal yr BP, in the similar period withthe peat layer of the NYS deposited in different sedimentary environment, which is highlycoincident with the age of the Younger Dryas event that was the most significant cold climaticevent during the last deglacial warming and occurred between12.9~11.6ka. The coincidenceindicates that the formation of hard clay in the central NYS possibly related to the YoungerDryas event.The high abundance of freshwater algae (Concentricystis and Pediastrum) andTypha indicates that the hard clay is a freshwater deposit. The presence ofChenopodiaceae-Artemisia in the hard clay indicates that the study area was occasionally affected by seawater during the formation of hard clay. Dinoflagellate occurs in increasingabundance in the upper and lower section of hard clay suggesting the study area had growingmarine influence during the early and late stage of the formation of hard clay. The reciprocalvariation law between freshwater algae and land-flora shows that the hard clay was formed inseveral stages. The sporo-pollen assemblages (Artemisia-Typha-Pinus-Poaceae-Monoletesand Pinus-Artemisia-Poaceae-Monoletes-Typha) from hard clay show that the study area wasin a cold and humid environment during the formation of hard clay, and characterized bymeadow present in the riverine wetlands with coniferous and broadleaved mixed forest.High-resolution shallow sub-bottom profiles reveal a prominent moundy low-anglebidirectional (landward and seaward) progradational mud clinoform deposit distributedalongshore off the southeast coast of Liaodong Peninsula, which is up to14m in thicknessand thins seaward and landward to less than2m. The clinoform deposit occurs about180to300km away from the Yalu River mouth between the northeast of the Dalian Bay andsouthwest of the Changshan Islands at a depth of20–40m. The mud deposit represents aHolocene Highstand System Tract sequence formed after the sea-level highstand at6.5ka andis mainly derived from Yalu River and Dayang River. The resuspension, transportation anddeposition of the sediments off the southeast coastal area of Liaodong Peninsula is mostlycontrolled by marine processes, such as tides, waves and the LCC.The paleoenvironment evolution in the Liaodong Peninsula coastal mud area sinceLGM is largely dominated by sea-level changes and sediment supply. The peat layer, formedabout10383to10396cal yr BP, is different from the peat layer related to the Younger Dryasevent in NYS, which results from a few stagnated periods of sea level existed betweenMWP-1B event and MWP-1C event.更多还原