【作者】 李艳；

【导师】 李安春； 黄朋；

【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， 2011， 博士

【摘要】 本文通过对908底质调查为主的三次北黄海海洋地质调查获得的大量沉积物样品的粒度和矿物分析,并结合AMS14C测年数据,探讨了北黄海末次冰消期以来的沉积特征及演化模式,并由此分析了北黄海物质来源和沉积环境。北黄海表层沉积物粒度分析结果显示:研究区沉积物以砂、粉砂质砂、砂质粉砂为主,粉砂分布范围较小,泥分布范围最小。研究区自西南向东北,沉积物粒径逐渐变粗,由粉砂和泥质沉积逐渐转变为东北部的砂质沉积。通过粒度分析可将北黄海划分为5个分区,分别受到物源、水动力环境等因素的控制。粘土矿物分析结果表明,北黄海现代粘土矿物中,伊利石含量占绝对优势,其次为蒙皂石、绿泥石和高岭石。K型聚类分析成功识别出北黄海细颗粒沉积区粘土组合和北黄海粗颗粒沉积区粘土组合。其中细颗粒沉积区粘土矿物主要来源于黄河细颗粒物质;粗颗粒沉积区的粘土矿物则主要受到鸭绿江的影响,后者为该区提供丰富的伊利石和绿泥石。粘土矿物的空间分布与黄海环流体系有密切关系:黄海暖流和山东半岛沿岸流对细颗粒区粘土矿物的输运其主要作用,而辽东沿岸流则为大连湾附近海域提供了较多的来自于鸭绿江的伊利石和绿泥石,北黄海中部海域蒙皂石的显著富集可能与北上的黄海暖流有关。对63-125μm粒级(个别扩大到63-250μm粒级)碎屑矿物镜下鉴定结果表明,北黄海现代碎屑矿物中轻矿物含量较高,达到97%,重矿物含量较少,平均仅有3%。普遍出现的轻矿物有6种,以长石、石英为主,重矿物共29种,普通角闪石、绿泥石、绿帘石和白云母含量较高;研究区东北部砂质区间内矿物分布的重要控制因素是强潮流场作用下的动力分选,物质来源有鸭绿江河流输入和全新世前夕海侵造成侵蚀改造的残留沉积;大连湾-长山列岛附近海域,由于水深较浅形成的较强动力分选是区间内矿物分布的主控因素,物质来源主要是近岸及附近岛屿剥蚀;西南部细颗粒沉积区以片状矿物富集为主要特征,主要在山东半岛沿岸流及其回流以及黄海暖流的作用下接受较多的黄河沉积物;研究区中部的沉积特征显示,那里是冬季黄海暖流进入北黄海并经由渤海海峡进入渤海的通道,其在一定程度上阻挡了东西和南北两部分海域物质和水体交换,呈现通道沉积的特征。北黄海现代细颗粒沉积区两个岩芯的粒度组成、矿物分布特征以及AMS14C年代信息,揭示了该区域自末次冰消期以来的沉积环境和沉积演化模式。结果表明:两个岩芯沉积序列相关性较好,根据其岩石学及矿物学特征,可被分为4个沉积单元,分别对应冰后期海侵不同阶段。沉积单元4(11.5 ka之前)以砂组分的富集为最显著特征,且被推断为新仙女木时期(Younger Dryas)的近岸浅水区沉积。沉积单元3(11.5-9.6 ka)呈现一个向上逐渐变细的沉积序列,其沉积物主要来源于周边河流(比如黄河)以及沿岸侵蚀,与全新世早期海侵作用密切相关。自沉积单元2(9.6-6.4 ka),岩芯开始呈现稳定的细颗粒沉积,此时细颗粒沉积物可能源于山东半岛水下三角洲的供给。沉积单元1(6.4 ka以后)于全新世中期海平面达到最大之后形成,主要自黄海环流的带动下,接受较多的黄河物质。总之,北黄海现代沉积物主要是陆源沉积,由周边河流携带而来,其中黄河、鸭绿江等较大河流起主要作用,另外还有近岸侵蚀、海底侵蚀等也为北黄海贡献了较多的粗颗粒沉积物。东部的强潮流、中部的黄海暖流和南部的沿岸流共同主宰着那里的沉积分布格局。更多还原

【Abstract】 In order to identified the provenance and sedimentary environment, and reconstruct the depositional history of ancient epicontinental seas, it is important to understand sediment characteristics and transport processes of modern and cores deposition in the continental shelf environments. A large number of surface and core sediments were obtained during cruise to the North Yellow Sea (NYS). Base upon grain size, mineral analyses, and AMS14C and 210Pb dating, the sediment characteristics and evolution were discussed, and the provenance and sedimentary environment were analyzed in addition. Grain size of surface sediment samples were analyzed, indicating that the surface sediments in the study area could be identified as mud, silt, sandy silt, silty sand and sand, and became coarser and coarser from southwestern part to northeastern. The NYS could be divided into five sediment environmental zones according to grain size analysis, which was dominated by factors such as provenance and hydrodynamic environment respectively.The clay minerals in the <2μm fraction of surface sediment samples from the NYS have been identified. Illite was the most abundant component in the modern clay minerals of NYS, followed by smectite, chlorite and kaolinite. The results of the K-means clustering analysis discriminated the fine-deposition in the western part and the coarse-deposition in the northeastern part on the basis of clay mineral assemblages. Fine materials from Huanghe, as well as west coastal erosion and other rivers supplied clay minerals for western part of NYS, while Yalujiang River offered plenty of illite and chlorite with clear abrasive edge and lower crystallography index for northeastern NYS. The spatial distribution of clay minerals has a close relationship with the local circulation system. The Yellow Sea Warm Current (YSWC) and Yellow Sea Coastal Current (YSCC) exerted good control on transportation clay minerals in western NYS. Liaonan Coastal Current (LCC) brought more illite and chlorite from Yalujiang to deposit near Dalian Bay. The enrichment of smectite in the central part of the investigated area was considered to be northward transported by YSWC.Modern detrital minerals in NYS were absolutely dominated by light minerals (97% in average). Mineral assemblages were characterized by relatively high content of feldspar, quartz in light minerals and hornblende, chlorite, epidote, muscovite in heavy minerals. In sandy deposition of northeastern NYS, the dynamic sorting under strong tidal currents largely affected the distribution of detrital minerals, which derived from Yalujiang River and residual deposition before Holocene. Near the Dalian Bay—Changshan Islands area, dynamic sorting in shallow water exerted a dominant control on detrital minerals distribution, and sediments were mainly derived from the coastal erosion. Schistose minerals were extremely enriched in fine-grained deposition in southwestern NYS, hydrodynamic was weak therein and differentiation during long-distance transporting was responsible for the distribution of detrital minerals, which was considered to be subjected to great influence from Yellow River. The center of NYS, which was a multi-source deposition zone affected by multiple factors, was speculated to be the response of the YSWC, which obstruct water and sediment exchange between west and east regions as well as south and north regions to a large extent.To decipher the sedimentary evolution and sedimentary environment changes since the Last Deglaciation, two gravity cores, B-L44 and B-U35 from the western NYS were analyzed in grain size, clay minerals, detrital minerals, and 14C dating. The two cores are correlated with each other, and the succession observed are divided into four depositional units in lithology and mineral assemblages, which record the postglacial transgression. Depositional unit 4 (DU 4) (before 11.5 ka) was characterized by great enrichment of sand, and was diagnosed as nearshore deposits in shallow water during the Younger Dryas Event. DU 3 (11.5-9.6 ka) displayed a fining-upward succession composed of sediment from local rivers, such as Yellow River, and from coastal erosion, clearly related to the early Holocene transgression. Stable fine deposition (DU 2) in NYS began to form at about 9.6 ka and received direct supply of fine materials from the Shandong subaqueous clinoform. It is believed that the Yellow Sea circulation system played a major role in controlling the formation of DU 1 (after 6.4 ka) after the sea level maximum.In a word, the modern sediment in the NYS is dominated by terrigenous depositions from such as Yellow River, Yalujiang River and so on. Additionally, erosion, including coastal erosion and sea erosion, contributed to the NYS more coarse particles. The strong tidal current in eastern, the YSWC in central and YSCC in southern jointly dominated the distribution pattern in the NYS.更多还原