基于有孔虫和稳定同位素记录的晚第四纪东北印度洋古海洋变化
文献类型：学位论文
| 作者 | DHANUSHKA DEVENDRA |
| 答辩日期 | 2019 |
| 授予单位 | 南海海洋研究所 |
| 导师 | 向荣 |
| 关键词 | 底栖有孔虫，稳定同位素，东北印度洋，深层水通风，古生产力 |
| 学位名称 | 硕士 |
| 学位专业 | 海洋地质 |
| 其他题名 | The Late Quaternary paleoceanographic changes in the northeastern Indian Ocean based on foraminiferal and stable isotopic records |
| 英文摘要 | The bottom water of the Indian Ocean is closely related to the evolution of the Antarctic bottom water mass, which is a key component of the world thermohaline circulation. Here we present the first detailed epibenthic d13C and benthic foraminiferal assemblage records from two northeastern Indian Ocean cores (the central Bay of Bengal and the Andaman Sea) in order to provide insight into the palaeoceanographic changes including palaeoproductivity and bottom water ventilation changes during the last 56 kyr and during the Holocene. According to the records from central BoB core, we identified three different palaeoceanographic stages, clearly differentiated by significant variations in benthic foraminiferal assemblages and epibenthic d13C records. Our results infer that productivity was generally higher during glacial periods than during the Holocene. Comparison of the benthic foraminiferal assemblage distribution and epibenthic d13C records shows the significant relationship between productivity and ventilation on glacial-interglacial timescales. Productivity gradually increased during the period between 56 - 27.5 kyr. During this period, the dominance of Melonis spp. and O. umbonatus were correlated with conditions of intermediate to high surface productivity and moderate bottom water ventilation. Increased higher equatorial productivity and low bottom water ventilation during the period between 27.5 -15 kyr are supported by epibenthic d13C and faunal records. During this period, the dominance of benthic foraminifera assemblages characterized by Uvigerina peregrina indicates sustained continuous phytodetritus flux to the seafloor from enhanced surface water productivity and relatively low bottom water ventilation. The absence or minimum occurrences of high productivity indicating Uvigerina peregrina, the dominance of intermediate to low productivity indicating fauna, and higher epibenthic d13C records suggest low productivity and active deepwater ventilation after 15 kyr.Distinct d18O decrease observed during the mid-Holocene (~8-6 kyr BP) and the beginning of the deglaciation (~16-14) may suggest the surface salinity decrement in the central Bay of Bengal waters probably due to intensified Indian southwest monsoon precipitation. Concurrent river discharge and rising sea levels begin during the Holocene are indicated by low d18O of G. ruber at the core site. The combined effect of increased sea surface salinity and decreasing sea surface temperature explained by planktonic d18O records. The last glacial maximum (LGM) to Holocene planktonic d18O shift (1.64‰) exceed the ice volume effect by 0.42‰ due to the decreasing glacial SST by ~1.5 ?C and/or ? 0.5‰ increase in SSS. In contrast to d18O records, d13C records from YDY05 are not clearly explain the glacial-interglacial changes. Benthic d13C variation and d13CPlanktic-Benthic offset variation in our core site explained significant variations in source water characteristics during the glacial-interglacial. Drastic depletion in d13C records of deep waters during the glacial exhibit significant reduction of North Atlantic Deep Water (NADW) intrusion and the progressive influx of Antarctic Bottom Water (AABW) with low d13C to the central BoB. The large d13CPlanktic-Benthic offset during the glacial time suggest, more sluggish deep water circulation and more lower d13CPlanktic-Benthic during the Holocene suggest, enhanced deep water circulation in the central BoB.According to the high-resolution faunal records from Andaman Sea core, we identified three different paleoceanographic stages as named, early (11 to 8 kyr BP), mid (8 to 4 kyr BP) and late (4 kyr BP to present) Holocene. Abundant occurrences of high productivity indicating fauna, U. hispida during mid-Holocene and U. peregrina during late Holocene indicate enhanced surface water productivity and low bottom water ventilation. The faunal composition during the early Holocene characterized by M. barleeanum, B. aculeata, and G. subglobosa suggests intermediate surface productivity and moderate bottom water ventilation. Concurrent river discharge and rising sea levels begin during Holocene are indicated by low d18O of G. ruber at the site and suggest reduced convective mixing and intermediate surface water productivity. |
| 源URL | [http://ir.scsio.ac.cn/handle/344004/18121]  |
| 专题 | 南海海洋研究所_学位论文（硕士） |
| 推荐引用方式 GB/T 7714 | DHANUSHKA DEVENDRA. 基于有孔虫和稳定同位素记录的晚第四纪东北印度洋古海洋变化[D]. 南海海洋研究所. 2019. |
入库方式： OAI收割
来源：南海海洋研究所
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