碩士 / 國立臺灣師範大學 / 地球科學研究所 / 90 / Two deep-sea cores(MD982195, 31°38.33’N, 128°56.63’E, water depth 746m; CSH-2, 29°25.0’ N, 126°34’ E, water depth 703m) retrieved from the Okinawa Trough, Western Pacific were studied to unravel the high resolution (65-90 years; 30-140 years, respectively) paleoceanography and paleoclimate records of the Okinawa Trough for the last 40 kyrs. Proxies adopted in this study include alkenone index, carbonate fraction, and organic carbon content.
Core MD982195 (33.6 m long) shows continuous and homogenous sedimentation with two vocanic ash layers. The length of core CSH-2 is 7.3 m. Several 14C datings together with planktonic foraminiferal δ18O stratigraphy show the bottom of the cores are respectively down to stage 3(MD982195) and stage 2(CSH-2) in the last glacial period.
Carbonate stratigraphy in both cores shows the typical Atlantic pattern, which the carbonate content is high in the interglacial period and low in glacial time. Terrestrial organic matter concentration increase in the glacial period giving this area planty of nutrient. Obviously, the sedimentation character of the Okinawa Trough is heavily influenced by terrigeous input and its dilution effect. This trend is the same as those records recorded in other five cores along the western Pacific marginal seas.
The organic carbon content in both cores are quite high compare with other records in the South China Sea and Okinawa Trough. This is probably because of great terrestrial organic matter input and the water depth of the cores falls in the oxygen minimum zone in the water column where always have better preservation in organic matter.
The paleo-sea surface temperature (SST) record which is almost parallel with oxygen isotope curve shows that the SST of glacial time was about 5℃ cooler than that of interglacial time in the Okinawa Trough. Similar to other records of northern hemisphere, the lowest paleo-SST occurred at 17-18 ka in the last glacial maximum. The millennial paleo-SST fluctuation magnitude decrease gradually since the glacial period of time. The magnitude reaches 2℃ before IS. 8 but only 0.5℃ in the interglacial period of time. When we compare the record with oxygen isotope record, we can find there are several salinity change events in the last 40kyrs, which might be related to the input of the fresh water from China continent. The record also shows that there are two special paleo-SST change events. One is a 2℃ cooling event occure at 800-1500BP which is the same magnitude as the Younger Dryas event. The other is a warming event around 9000 BP, which might be the result of the strengthen of the Kuroshio current or regional hydrothermal effect. Both of them needs to be further studied.
| Identifer | oai:union.ndltd.org:TW/090NTNU0135014 |
| Date | January 2002 |
| Creators | Chen-yu Huang, 黃振祐 |
| Contributors | Horng-Sheng Mii, 米泓生 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 99 |
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