末次冰期以来西赤道太平洋边缘海古气候变化研究

IOCAS-IR > 海洋环流与波动重点实验室

	末次冰期以来西赤道太平洋边缘海古气候变化研究
	李铁钢
学位类型	博士
	1991
学位授予单位	中国科学院海洋研究所
学位授予地点	中国科学院海洋研究所
学位专业	海洋地质学
摘要	本文所研究的区域是西赤道太平洋的两个边缘海盆-苏禄海和南中国海。这两个边缘盆地具有明显不同的水文特征，南中国海底层水冷（<4 ℃）并且通气较好（溶解氧浓度>1.75ml/l），而苏禄海底层水温暖（>10 ℃）并且含氧量低（溶解氧浓度<1.25ml/l）。这些不同的水文特征导致了不同的沉积环境，同时两个海盆的沉积记录也包含了这些水文条件在不同地质时间上如何变化的历史。笔者分别对南中国海的GGC-6孔（12°09'1''E，118°03'9''，水深2775米）和苏禄海的GGC-29孔（8°17'7''E，118°49'9''N，水深1535米）的浮游和底栖有孔虫动物群进行了系统地分析鉴定和统计，并用转换函数对古温度进行了分析，力求通过有孔虫化石群的面貌和定量古生态分析来反映古气候的变化。通过对浮游有孔虫氧同位素环境效应的分析来探索本区的古气候变化。此外还对沉积物中的有机碳和碳酸钙的含量进行了测试和分析。通过上述工作我们得出以下几点认识：1、氧同位素和古水温记录可分末次冰期和全新世两期，由于岩心的长度所限地质记寻年代较短为24000年左右。2、浮游有孔虫G.Grassaformis的最后出现是苏禄海末次冰期极盛时（～18000B.P）重要的地质界线。3、发现在北欧地区短暂寒冷的仙女木期（Younger dryas）在本区也有发现。这在一定程度上说明了仙女木期存在的全球性。4、本区末次冰期与全新世的夏季表层古水温相差不到2 ℃与CLIMAP（1976）赤道太平洋末次冰期以来古水温度的模拟结果相附。冬季表层水温相差较大为3.5 ℃左右。5、瓷质壳底栖有孔虫的繁盛和翼足类的大量保存是苏禄海冰期时底层暖水的良好指示标志。6、本区有机碳的含量反映了底层水含氧浓度的变化。高有机碳代表低氧浓度，低有机碳代表高氧浓度。南中国海一直受到西北太平洋水体的影响，致使其底层水一直处于充氧状态，只是在冰期最盛时稍有降低。而苏禄海底层水氧浓度较低，尤其是末次冰期极盛时隔绝状态加强，大量的降水使表层海水淡化分层，致使底层水缺氧状态加剧。7、本区做为西赤道太平洋的边缘海，其CaCO_3旋回模式却与太平洋相反，而与大西洋一致，即冰期碳酸钙含量低，全新世冰后期碳酸钙含量高。冰期陆源物质供应的加强和全新世浮游有孔虫生产力的提高是控制本区碳酸钙旋回的主要因素。此外，冰期海水溶解作用的加强是南中国海冰期低CaCO_3含量的另一个重要原因，而苏禄海的碳酸钙沉积受海水溶解作用的影响却很小。8、浮游有孔虫N.dutertrei的大量增加和相对较轻的δ~(18)O值说明冰期最盛时海水表面的盐度较低。末次冰期时东南亚地区东北季风加强西南季风减弱，由于特殊的地理环境使本区在冰期时降水大量增加。
其他摘要	The western pacific consists of a series of marginal basins that are separated from each other by sills of varying depths. Two of these marginal basins, the sulu sea and the south china sea, have strikingly different water mass properties. The sill which separates the south china sea from the west-Northern Pacific is 2500 m deep and allows pacific deep and intermediate water to enter the south china sea, but excludes pacific Bottom Water. As a result, South china sea bottom waters are cold (<4 ℃) and fairly well ventilated (dissolved O_2 concentration > 1.75ml/l). In contrast, the Sulu Sea is completely surrounded by a sill, most of which is shallower than 100m. The semi-isolated nature of the sulu sea results in water mass properties that are relatively uniform below 600m; bottom waters are warm (>10 ℃) and poorly oxygented (<1.25ml/l dissoved O_2). Theses different hydrographic settings result in very different depositional environments, and the sedimentary records from both basins contain the history of how these hydrographic conditions have changed through time. Two cores studied were taken at the GGC-6 core (12°09'1''E, 118°03'9'', water depth 2975m) from the south china sea and the GGC-29 core (8°17'7''E, 118°49'9''N, water deep 1535m) from the sulu sea respectively. oxygen isotope, planktonic and bethonic foraminifer, Carbonate and organic carbon records have been analysed for the two cores. The preliaminaly study is on stratigraphy for paleoenvironmental research. The following conclusion were obtained through this study: 1. The last Glacial age and the Holocene were identified from the oxygen isotope and sea surface temperature (SST). The time range is about 24000 years B.P. 2. The last occurrence of the planktonic foraminifer G. crassaformis occurs near the end of Glacial stage two in the sulu sea. 3. The Younger Dryas is an abrupt short-term cooling occured during the last deglciation. This cooling was originally recognized in northern European climate records. We observed a Younger Dryas cooling in this study. It clearly demonstrates that this is a global climatic event. 4. Sea surface temperature (SST) agreed with the average glacial/interglacial change in the equatorial pacific estimated by CLIMAP (1976). This change is 2-4 ℃. 5. The prosperous porcelainous bethonic forminifer and large preservation of pteropod standed for Glacial bottom water warming in the sulu sea. 6. This work showed that the organic carbon content is higher in glacial age sediments and lower in Holocene sediments. The Glaial/Interglacial differences reflect the changes in preservation. The enhanced isolation of the sulu sea during the last glacial resulted in lower bottom water oxygen concentration and hence better preservation of organic matter. 7. It is clear that carbonate is lower in glacial age sediments and higher in Holocene sediments. this is the opposite pattern typically observed for the pacific. The enhanced terrestrial offerings in Glacial age and the increased surface productivity during Holocene are mainly controlling factors. In addition, Species dissolution indices was used to determine that dissolution is the important factor controlling Glacial/Interglacial difference in carbonate accumulation in GGC-6 core. 8. An increase in the abundance of the planktonic foraminifer N. dutertrei and relatively light δ~(18)O Values in planktonic foraminifer suggest that surface water salinites were reduced in the area during the last glacial maxium. NE monsoon was more intense and sw monsoon was reduced during the last glacial age. Because of special geography environments, the increased rainfall was emerged in the area from the last glacial maximum to the transition to interglacial conditions.
页数	64
语种	中文
文献类型	学位论文
条目标识符	http://ir.qdio.ac.cn/handle/337002/467
专题	海洋环流与波动重点实验室
推荐引用方式 GB/T 7714	李铁钢. 末次冰期以来西赤道太平洋边缘海古气候变化研究[D]. 中国科学院海洋研究所. 中国科学院海洋研究所,1991.

条目包含的文件
文件名称/大小	文献类型	版本类型	开放类型	使用许可
N86281.pdf（2679KB）			限制开放	--	浏览