【作者】 杨競红；

【导师】 王颖；

【作者基本信息】 南京大学 ， 自然地理学， 2006， 博士

【副题名】宝应钻孔沉积物的地球化学记录

【摘要】 苏北盆地是在扬子地块的基础上于晚中生代形成的以箕状断陷为特点的大型复合沉积盆地。盆地中断裂构造十分发育,这些深大断裂控制了第三纪晚期以后的沉积作用。新第三纪随着青藏高原的隆升和边缘海的张裂,中国东部整体沉降。紧邻边缘海的苏北平原是南黄海盆地的陆上部分,西界为一系列的低山丘陵呈弧形环绕着平原。平原内水网密集,淮河、沂河等众多河流流经其间并东入黄海。京杭大运河穿其西部而过,北有废黄河故道,南有长江。东侧有两列古海岸贝壳砂堤,它们大体上平行于现今海岸方向分布,海拔3～5m,是海退海岸的象征,在平原西部有洪泽、高邮等众多湖泊形成的湖泊群。本论文研究的是介于古贝壳堤西侧与湖泊群东侧之间的平原成因。2004年夏在苏北平原低洼处,距现代海岸120km的宝应县望直港进行了钻孔取样（BY1,33o14’21”N, 119o22’41’’E）,钻孔进深144.98 m,实取沉积柱为96.81 m。对选取的代表性样品进行了矿物鉴定和地球化学分析,包括11种常量元素SiO₂、Al₂O₃、TiO₂、Fe₂O₃、MgO、MnO、CaO、K₂O、Na₂O、P₂O₅和SO₂、34种微量元素（包括稀土元素）、沉积物有机碳、氮元素含量及其同位素进行了分析。电子探针及X射线衍射分析表明,宝应钻孔沉积物主要由石英、长石、粘土矿物、碳酸盐矿物及少量氧化物矿物组成。粘土矿物包括伊利石、蒙脱石、斜绿泥石和高岭石;碳酸盐矿物有文石、方解石和白云石;氧化物为刚玉、磁赤铁矿及赤铁矿。宝应粘土矿物种类与黄河及长江的粘土矿物组合十分接近,兼有上述两地的特征而具有过渡性,蒙脱石含量高的层段可能受古黄河物质的影响较大,而含碳酸盐矿物较多的层位应来源于长江中下游流域的灰岩基底。钻孔B/M界线之下（4078 m～4530 m）的泛滥平原河湖相沉积物中局部地段富含铁锰鲕粒,其主要矿物组成为蛋白石、铁的氢氧化物（包括纤铁矿、水纤铁矿、针铁矿、水针铁矿,统称褐铁矿）、铁锰氧化物（包括硬锰矿和软锰矿,以硬锰矿为主）及极少量的细小碎屑矿物（钾长石、蚀变黑云母、含铁白云母、锆石、独居石、金红石和含钛磁铁矿）。该铁锰鲕粒层是在地表暴露和接着发生的大规模海进之间的、具有较强水动力的高能沉积环境下的产物,反映了近于B/M界线时本区有着频繁波动的气候和水动力变化,在0.78Ma之后,随着地磁的倒转本区拉开了大规模海侵的序幕。沉积物主元素质量分数分布模式为Si > Al > Fe > Ca > K > Mg > Na > Ti > Mn > P > S。与中国东部上地壳平均化学组成比较,其沉积物具有高Si、Ti、Mn、P、S,低Na、Mg、Al、K、Ca、Fe的特征。钻孔中海相沉积物较陆相沉积物明显含有较高的Mg、Ca、P、S这些海洋中的特征元素,与海洋生物及海水组成有着密切关系。海相沉积物常量元素组成与中国浅海沉积物相近,且高Mn、P、S,低Na。P含量介于半深海的冲绳海槽沉积更多还原

【Abstract】 The Northern Jiangsu Basin which has developed from the Yangtze plate since late Mesozoic times, is a large sedimentary basin composed of several small sub-basins shaped as a“dustpan”. It is dominated by deep faults which controlled the sedimentation since late Tertiary. The west-tilting topography of East Asia was reversed with the uplift of the Tibetan plateau and the opening of marginal seas, resulting in an Asian fluvial system radiating from the uplifted center of the continent. The Northern Jiangsu Plain, which is above sea level, comprises the continental component of the southern Yellow Sea Basin. It is located on the northern side of the Yangtze River and south of Lan-Shan Tou cape, 32o10’-35 o 05’N, and 118 o 40’-120 o 30’E.Historical records and previous studies have indicated that the outer part of the Northern Jiangsu plain was formed from marine sedimentation during a Holocene high sea level period at 5000 a BP, as defined by a series of abandoned shell beach ridges. These are about 200 km long from north to south, and located some 60 km landward of the modern coastline. The present study is focused upon the formation of the inner part of the Jiangsu plain which is located inside of the beach ridges and to the west of the Grand Canal.Geomorphic features relating to the formation of the inner plain west to the Fan-Gong dike, include (1) A series of surrounding rocky hills forming an arc-shaped embayment. (2) A series of lakes, such as Hongze, Gaoyou, and Shaobo Lake, located to the west of the Grand Canal, which are almost connected to each other either by lowland or swamps. Indeed, the Grand Canal was constructed partly utilizing the pre-existing channels connecting these lowland swamps and lakes (3) Several rivers have produced deltaic forms on the western side of the lakes;(4) A series of artificial islands have been constructed upon the natural bars or barriers located in the lakes and wetlands, and are locally termed Duo, Dun or Wei (meaning artificial bars or crossways in Chinese). These are now valuable lands for settlements for local people living in the wetland areaa. All of the islands or barriers are aligned in a North to South direction i.e. parallel to the present coastline. Sea shells and their fragments have been found on these islands indicating a marine origin.更多还原