臺灣博碩士論文加值系統

本研究藉由測量加勒比海TT9108-1GC岩芯過去兩萬年以來浮游性有孔蟲G. sacculifer殼體中的δ44Ca、δ18O與Mg/Ca比的比值，來探討δ44Ca和海洋環境因子之間的關係。結果顯示G. sacculifer δ44Ca的變化與海表溫度（SST）和海表鹽度（SSS）有關。經結合有孔蟲之δ18O與Mg/Ca比值，和古海水面變化紀錄所重建的古海表鹽度顯示過去兩萬年以來加勒比海之SSS介於36.5~39.5 psu，呈現顯著變化。扣除溫度分化效應後，G. sacculifer之鈣同位素組成變化與SSS呈現0.27±0.08 ‰/psu之關係，在統計上具有顯著的相關性，但與環境碳酸根離子濃度在統計上並無顯著相關性。此外，G. sacculifer殼體中的鈣同位素比值的變化也可能與Rayleigh fractionation有關。溫度與鹽度控制了G. sacculifer的新陳代謝速率，改變其造殼過程中消耗液泡中鈣離子之比例，間接影響G. sacculifer殼體的鈣同位素比值。基本上本研究無法由Lemarchand et al.（2004）的「速率控制分化」模型來解釋；而支持有孔蟲在造殼過程中會攝取海水，在體內形成獨立的液泡並調節其酸鹼度之模式（Erez, 2003）。

The δ44Ca, δ18O, and Mg/Ca ratios of fossil G. sacculifer over the past 20 ka extracted from a Caribbean core, TT9108-1GC, have been measured in order to examine the possibility of using δ44Ca as a proxy for paleoceanography. Our results indicate that the δ44Ca of G. sacculifer varies as a function of sea surface temperature (SST) and sea surface salinity (SSS). The Caribbean Sea SSS, reconstructed by combining the δ18O and Mg/Ca ratios of G. sacculifer and sea level change data, shows significant fluctuations between 36.5 and 39.5 psu during the last 20 ka. After isolating the temperature effect, the δ44Ca of G. sacculifer exhibits a positive correlation with SSS, ca 0.27±0.02 ‰ per 1 psu. On the other hand, no significant relationship is observed between δ44Ca and seawater [CO3=]. Moreover, variation of G. sacculifer δ44Ca can also be explained using a Rayleigh fractionation model. As a function of temperature and salinity, the metabolic rate may influence the utilization of vacuole Ca++ in G. sacculifer, resulting in different δ44Ca values. The results of this study are inconsistent with the “rate-controlled fractionation model” of Lemarchand et al. (2004), instead, the results are more in-line with the foraminiferal biomineralization model of Erez (2003), where δ44Ca reflects the adjustments of temperature, salinity, and pH of seawater isolated in vacuoles during the growth of G. sacculifer.

總目錄
摘要....................................................................................................................................I
Abstract. ...........................................................................................................................II
致謝.................................................................................................................................III
總目錄.............................................................................................................................IV
章節目錄.........................................................................................................................IV
表目錄.............................................................................................................................VI
圖目錄............................................................................................................................VII

章節目錄
第一章 緒論...................................................................................................................1
1.1 鈣同位素組成之慣用符號表示法..................................................................2
1.2　前人對於鈣同位素分化原理的研究..............................................................2
1.3　目前鈣同位素研究上的爭議與本研究所扮演之角色................................13
第二章 實驗方法與年代模式.....................................................................................15
2.1　標本................................................................................................................15
2.2　標本前處理....................................................................................................16
2.3　氧碳同位素分析............................................................................................17
2.4　微量元素分析................................................................................................17
2.5　鈣同位素分析................................................................................................17
2.6　年代模式........................................................................................................21
第三章　實驗結果.........................................................................................................23
3.1　氧碳同位素的分析結果................................................................................23
3.2　微量元素的分析結果....................................................................................23
3.3　鈣同位素的分析結果....................................................................................23
第四章　討論.................................................................................................................26
4.1 數據之重取樣................................................................................................26
4.2 古海表水溫度之換算....................................................................................26
4.3　古海表水鹽度之推估....................................................................................29
4.3.1　扣除δ18O temp後所得之δ18O sw...............................................................29
4.3.2　扣除δ18O sea level後所得之δ18O salinity......................................................29
4.3.3　古海水鹽度的換算...................................................................................29
4.3.4　SSS重建過程中可能造成的正回饋.......................................................31
4.4　古海表水碳酸根離子濃度之推算................................................................32
4.5　有孔蟲Δ44Ca與SST之關聯性...................................................................36
4.6　有孔蟲Δ44Ca與[CO3=]之關聯性.................................................................36
4.7　有孔蟲Δ44Ca no Temp與SSS、[CO3=]之關聯性........................................... 38
4.8　由有孔蟲的造殼機制來解釋鈣同位素分化和海水[CO3=]之關係.............41
4.9　由熱力學平衡分化模型來解釋鈣同位素分化和SSS之關係...................44
4.10 以Rayleigh fractionation模型解釋鈣同位素分化和SST與SSS之關係....46
第五章 結論.................................................................................................................49
參考資料.........................................................................................................................50

表目錄
表(2-1) 本研究使用的岩芯的年代模式.....................................................................22
表(3-1) 岩芯各深度G. sacculifer之殼體鈣同位素比值、氧碳同位素比值、鎂
鈣元素比與鍶鈣元素比測量結果.................................................................25

圖目錄
圖(1-1) 生物碳酸鈣與無機碳酸鈣之鈣同位素分化與溫度之關係...........................3
圖(1-2) 無機方解石之鈣同位素分化與碳酸根離子濃度之關係...............................6
圖(1-3) 實驗室養殖之G. sacculifer與海洋現生之G. sacculifer殼體鈣同位素分
化與溫度之關係.............,.................................................................................7
圖(1-4) 鈣板藻養殖實驗中殼體鈣同位素分化與溫度之關係...................................9
圖(1-5) 無機方解石、鈣板藻與有孔蟲殼體鈣同位素與環境碳酸根離子濃度之
關係.................................................................................................................10
圖(1-6) 鈣板藻造殼過程中攝取鈣離子之示意圖.....................................................11
圖(1-7) 岩芯頂部12種浮游性有孔蟲殼體鈣同位素分化與古海水表溫度之關係.....................................................................................................................12
圖(2-1) 本研究之岩芯TT9108-1GC位置圖.............................................................15
圖(2-2) 以岩芯ODP180 1115B同一深度（1H2W 140-142）之有孔蟲
G. sacculifer進行鈣同位素測量再現性之測試.............................................19
圖(2-3) 鈣同位素之向量空間幾何解法.....................................................................19
圖(2-4) 全球海水鈣同位素組成分佈圖.....................................................................21
圖(3-1) G. sacculifer之δ18O、δ13C、Mg/Ca值、Sr/Ca值與Δ44Ca變化曲線.........24
圖(4-1) 有孔蟲δ18O、Mg/Ca值、冰帽體積效應對海水氧同位素的影響、冰
芯pCO2紀錄與Δ44Ca變化曲線之原始資料與重取樣後之資料.................27
圖(4-2) 有孔蟲δ18O曲線、古海水表溫度曲線、冰帽體積效應對海水氧同位
素的影響與δ18O salinity變化曲線....................................................................28
圖(4-3) 對Data @ NASA GISS: Global Seawater Oxygen-18 Database資料庫中
47筆1950年以來加勒比海海域之海水δ18O值與海水鹽度資料進行
迴歸分析.........................................................................................................30

圖(4-4) Schmidt et al.（2004）以G. ruber之δ18O扣除溫度效應與冰帽體積效
應所求得的Δδ18O Ice Volumn Free-SeaWater値變化曲線與本研究推估之古海
水鹽度變化曲線.............................................................................................31
圖(4-5) 古海水表溫度變化曲線、古海水鹽度變化曲線、冰芯pCO2紀錄與古
海表碳酸根離子濃度變化曲線.....................................................................35
圖(4-6) 有孔蟲殼體分化係數Δ44Ca與古海水表溫度之迴歸分析圖.....................37
圖(4-7) 有孔蟲殼體分化係數Δ44Ca與古海表碳酸根離子濃度之迴歸分析圖.....37
圖(4-8) 25˚C下之有孔蟲分化係數Δ44Ca no Temp.......................................................38
圖(4-9) 以古海水鹽度與古海表碳酸根離子濃度做為變數，有孔蟲分化係數
Δ44Ca no Temp做為因變數之複迴歸分析圖.....................................................39
圖(4-10) 有孔蟲殼體分化係數Δ44Ca no Temp與古海水鹽度之迴歸分析圖................40
圖(4-11) 有孔蟲產生液泡與進行造殼之示意圖.........................................................42
圖(4-12) 有孔蟲進行低鎂碳酸鈣沉澱之示意圖.........................................................43
圖(4-13) 利用Mucci（1983）的方解石之溶解度對溫度與鹽度之關係式，理論
計算在25˚C下、鹽度在35~40psu之間，方解石溶解度的變化值..............44
圖(4-14) 利用Rayleigh fractionation模型來描述在不同的鈣離子使用率下，殘
餘之鈣離子與沉澱之碳酸鈣整體的鈣同位素組成.....................................47

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