闽浙近岸泥质区全新世气候-环境变化的脂类生物标志物记录

Lipid biomarkers widely dotted in marine sediments, as their atomic composition and molecular structure accurately record a large amount of information about the biological characteristics and vital activities of the original organisms, are often used to reconstruct the paleoclimatic and paleoenvironmental conditions. This study intends to select the core ECS-1302 in the muddy area of the East China Sea coast. The top 30.2 m length core is formed shallowly in three sedimentary environments: the tidal flat to the shore deposits affected by tide in the early Holocene (about 11.5~10.0 cal kyr BP), the estuary bay deposits (about 10.0~7.7 cal kyr BP), and the inner shelf mud deposits (about 7.7 cal kyr BP to the present). This project will analyze and compare the multiple parameters of lipid biomarkers, especially for glycerol dialkyl glycerol tetraethers and long-chain alkyl diols, in the Holocene sediments. On the basis of comparing the existing historical research results of sedimentary evolution in the area and clarifying the influence of early diagenesis, we will further describe the regularity of the changes in organic matter sources and sinks in the muddy area of the East China Sea in the Holocene, and reconstruct the marine sedimentary records of paleotemperature and humidity in the East China Sea inner shelf and its adjacent continents. Furthermore, we will focus on deciphering lipid biomarkers records in special climate-environment periods such as the 8.2 cal kyr BP cold event, the mid-Holocene warm period, the Medieval Warm Period and the Little Ice Age, and exploring the East Asian land-sea temperature linkage mechanism and the factors affecting rainfall in the mid-lower reaches of the Yangtze River.

海洋沉积物中星罗棋布的脂类生物标志物的原子组成和分子结构确切不移地记录了母源生物体特征和生命活动的大量信息，常被用来重建古气候-环境变化。本研究拟选取闽浙泥质区钻孔ECS-1302作为研究对象，该钻孔30.2m以浅依次为全新世早期约11.5~10.0cal kyr BP的潮坪至受潮汐影响的滨岸沉积、约10.0~7.7cal kyr BP的河口湾沉积和约7.7~0cal kyr BP的内陆架泥质沉积。本研究将重点对该钻孔约11.5cal kyr BP以来岩芯沉积物中丰富的甘油双烷基甘油四醚和长链二醇多项指标参数进行详尽的研究；在分析早期成岩作用影响的基础上，结合区域地质背景，阐明不同来源有机质的“源-汇”过程，解译东海内陆架及其临近大陆古温度和湿度的高分辨率海洋沉积记录；聚焦揭示诸多特殊气候突变事件时期的脂类生物标志物记录，探索东亚海陆温度联动变化机制以及长江中下游流域降雨影响因素。

东海内陆架有机质“源-汇”过程研究缺少区域沉积演化背景约束，且该区域在全球海洋温度重建数据库中缺乏代表性指标重建记录。为此，本研究以大量高分辨率浅层地震剖面和钻孔岩心为依托，厘定了MIS 5以来浙江近岸自下向上依次发育了潮下带至内陆架沉积、滨海至潮坪沉积、砂质河流/潮河沉积、河口湾湾心细颗粒泥质沉积和湾口粗颗粒砂质沉积、海岸-陆棚沉积和中陆架潮流沙脊、闽浙泥质体。发现在河口湾湾心沉积发育早期，海水侵扰影响较弱，陆源（包含河流和土壤源）有机质贡献较多；早全新世海平面持续上升的沿海-陆架环境，东亚冬季风减弱，陆源有机质贡献持续减少；中全新世最大海泛面形成以后，现代环流体系主导了长江源沉积物发育闽浙泥质体，陆源有机质贡献较少；约2 ka之后，叠加人类活动和ENSO事件等影响，长江三角洲向海进积作用加速，陆源有机质贡献再次增加。基于大量表层样品证实长链二醇指标（LDI）可以很好的应用于东海受长江冲淡水强烈影响以外海域偏向秋季节的海水表层温度（SST）重建。进而利用LDI重建了东海内陆架约14000年以来SST记录，呈现了一个滞后的全新世大暖期（约8~4 ka），识别了新仙女木(YD)、10.3-ka?、8.2-ka、4.2-ka和小冰期(LIA)等系列冷事件；认为海平面上升造成研究区Bølling–Allerød和8.2-ka事件结束期SST的阶梯式上升，水深增加缓冲了YD和8.2-ka等冷事件造成的SST降温幅度。本项目为厘清海陆相互作用和全球气候变化影响下内陆架有机碳埋藏规律、验证气候模式模拟实验提供了可靠的地质资料。