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冲绳海槽中部地区沉积物特征及对沉积环境的分析
张丹丹
学位类型硕士
导师曾志刚
2017-05-24
学位授予单位中国科学院大学
学位授予地点北京
学位专业海洋地质
关键词冲绳海槽 地球化学特征 粒度 物质来源 沉积环境
摘要冲绳海槽是位于中国东海陆架与琉球岛弧之间的正在扩张的弧后盆地,该地区具有独特的地理位置及构造演化,其物质来源及水动力强弱变化对于认识该地区的环境演化过程具有重要的意义。
本文基于AMS14C高精度测年,通过对柱状沉积物HOBAB2–S2的粒度、微量元素、稀土元素和主量元素的分析,对冲绳海槽中部地区5300年以来的物质来源和沉积环境进行了初步探究。通过对沉积物岩芯的粒度特征分析得知,5300年以来沉积物的物质来源稳定,源区未发生明显的变化。研究区域沉积物的地球化学特征指示沉积物具有较强的陆源属性,为了进一步确定陆源物质的来源,文中将该沉积物与不同物源区沉积物的元素特征进行对比分析,通过分析可得出,沉积物陆源物质主要来自于中国台湾,并混合了中国大陆东部多个源区的物质。
通过对研究区沉积环境,尤其是水动力(黑潮)强弱的指示参数——粒度特征的研究发现,岩芯粒径变化分为四个阶段;同时将主量元素沉积通量作为环境变化指标,其表现出与粒径变化一致性的特征,按变化趋势可将沉积过程分为四个阶段:阶段I(5300–3813年),黑潮强度减弱,沉积量较少,处于较低值;阶段II(3813–2699年)期间,黑潮强度较弱,处于相对波动状态,而此时的沉积速率较高,沉积量增多;阶段III(2699–970年)期间,水动力条件稳定,沉积速率减慢,沉积物质堆积量减少;阶段IV(从970年至今),水动力(主要为黑潮)强度增强,并伴有减弱趋势,沉积时期沉积速率较高,沉积量增加。
其他摘要The Okinawa Trough is an expanding back-arc basin between the East China Sea shelf and Ryukyu Island. The region has its unique location and tectonic characteristic. Therefore discriminating the provenances of the sediments and acknowledging the variation of the current are critical for studying on sedimentary environment evolution.
Based on the data of grain size, trace elements, rare earth elements and major elements coupled with high-precise AMS14C dating, this paper dealed with the provenance and sediment environment evolution of the middle Okinawa Trough for the last 5300a with the sample from the Core HOBAB2­­­­­­­­­­­–S2. The analysis ongeochemical characteristics showed their affinities to the terrigenous sediments in the study area. In combination with elements features of potential sediment sources, the sediments were mainly originated from Taiwan. Besides, they were also mixed with other materials from the eastern Chinese mainland.
The grain size and major elemental depositional fluxes were used to be the indicators of sediment environment, especially the vigor of local current (the current was mainly referred to Kuroshio Current in this paper). Since 5300 a BP, the major elemental depositional fluxes can be divided into four stages as well as the grain-size. As a consequence, according to the curves of grain-size and major elemental depositional fluxes, the conclusions were summarized as follows. Stage I (between 5300–3813 a BP), the strength of the Kuroshio Current (KC) weakened gradually and the input of sediment materials was relatively at a low level. Stage II (from 3813 to 2699 a BP), the strength of KC was weak and in a state of fluctuation. However, the depositional rate was in a high level, which indicated that the input of sediment matters increased. Stage III (from 2699 to 970 a BP), during which the sediment environment was in a stable station and featured with a slow sediment rate, indicating a decreased material input. Since about 970 a BP, the strength of KC strengthened and had a tendency of weakening. The high sediment rate showed the increase of the sediment.
语种中文
文献类型学位论文
条目标识符http://ir.qdio.ac.cn/handle/337002/136636
专题海洋地质与环境重点实验室
作者单位中国科学院海洋研究所
推荐引用方式
GB/T 7714
张丹丹. 冲绳海槽中部地区沉积物特征及对沉积环境的分析[D]. 北京. 中国科学院大学,2017.
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