渤海湾西北岸埋藏牡蛎礁礁顶上下沉积物中硅藻对“礁泥转换”古沉积环境的重建  

Diatom Analysis in the Top and Bottom Muddy Sediments of Buried Oyster Reef for the Reef Mud Conversion Palaeoenvironmental Reconstruction,Northwest Bohai Bay

作　　者：方晶[1,2] 王宏[2] 王福[2] 商志文[2] 胡克[3] 杨永强[3] 范昌福 王海峰[3] 

机构地区：[1]天津师范大学城市与环境科学学院,天津300387 [2]中国地质调查局天津地调中心,天津300170 [3]中国地质大学海洋学院,北京100083 [4]中国地质科学研究院矿产资源研究所,北京100037

出　　处：《沉积学报》2012年第5期879-890,共12页Acta Sedimentologica Sinica

基　　金：国家自然科学基金项目(批准号:40872106);中国地质调查局项目(编号:1212010911069)资助

摘　　要：渤海湾西北岸大吴庄牡蛎礁是近年来研究程度最高的礁体,天津空港物流中心牡蛎礁则是近年来新发现的礁体。该两处礁体上部的牡蛎个体内部充填的泥、个体之间的泥以及礁体上覆沉积泥层中的硅藻研究表明,礁顶上下(即礁体的上部—顶部和上覆沉积泥层的下部)均富含潮间带环境指示种的Auliscus caelatus,表明礁体发育后期和上覆沉积泥层的初期,均为潮间带环境。尽管如此,从礁顶向上覆沉积泥层转换方式在两处礁体却不相同:(1)大吴庄:Auliscus caelatus种向上逐渐减少,暗示着大吴庄剖面由礁体上部的潮间带中上部、直至上覆沉积泥层下部的潮间带上部、进一步向上覆沉积泥层上部的潮上带转化的趋势。(2)空港:牡蛎礁上覆沉积泥层出现了比例达6%～23%的河口咸水—半咸水种Achnanches brevipes,而下伏礁体内则未见该种,暗示此处泥层受河口作用显著影响。此种不同揭示了礁体停止发育的原因有所不同:在5 520cal BP时,大吴庄礁顶进入潮间带中上部,礁体经常脱离海水而发育停止;在约4 000 cal BP时,空港礁体所在位置因河流作用突然增强,在时间上看很可能是黄河改道在天津入海,古黄河携带大量泥砂入海,掩盖了潮间带的牡蛎礁而导致牡蛎礁发育停止。Dawuzhuang oyster reef is the deeply studied one in the recent years while Konggang oyster reef is a new one on the northwest coast of Bohai Bay. Diatom analysis of the muddy sediments filling into the oyster shells, be- tween the shells and in the overlying muddy layers all contained the Auliscus caelatus which indicated that the late de- velopment of the reef and the early stage of the overlying muddy layers are all belonging to the intertidal zone environ- ment. However, the reef-mud conversion was not the same in these two reefs. （1） The Auliseus caelatus in Dawuzhuang oyster reef decreased gradually from the top of the reef to the overlying muddy layers, which indicated an environment change from the middle to upper parts of intertidal zone, upper parts of intertidal zone to supratidal zone. （2） The Achnanches brevipes, indicating estuary environment, with the percentage of 6% -23% were found only in the overlying muddy layers of Konggang oyseter reef. It showed estuary influence in the muddy layers. The above differences revealed the reef-mud conversion was not the same in the two reefs. The Dawuzhuang oyster reef grew up to the middle to upper parts of intertidal zone in the year 5 520 eal BP, and development stopped with the gradual dis- appearance of the marine influence. The Konggang oyster reef grew up to the intertidal zone in the year 4 000 cal BP and was suddenly buried by the muddy and sandy sediments which maybe from the Yellow River. Therefore, the ＂reef-mud conversion＂ periods, which the oyster reefs stopped growing up and began overlaid by the mud layers, are 5 520 cal BP and 4 000 cal BP in Dawuzhuang and Tianjin Konggang, respectively. The seawater didnl quickly exit when the two reefs stop growing, and then 1.2m thick intertidal zone sediments and 2.9 thick la- goon-intertidal zone sediments respectively deposited in the two locations. The author speculated that the seawater completely withdraw from the two reefs were later than 4 700 and 1 100 years ago. The altitudes of the ma

关 键 词：渤海湾西北岸 大吴庄牡蛎礁 空港物流中心牡蛎礁 硅藻分析 潮间带 

分 类 号：P618.130.21[天文地球—矿床学] TE122.221[天文地球—地质学]