- 學位論文
浮游性有孔蟲稀土元素比值作為新古環境代用指標 – 以巴布亞新幾內亞三十六萬年以來之降雨紀錄為例
Planktonic foraminifera rare earth element ratios as a new paleoenvironmental proxy - a precipitation intensity in Papua New Guinea during the past 363 thousand years
摘要
稀土族元素在地球科學上有著廣泛的應用，是極為重要的示蹤劑。而有孔蟲殼體內的稀土族元素，被認為能紀錄下生活當時海水中稀土元素的信號。本研究建立巴布亞新幾內亞臨海，所羅門海MD05-2925岩芯過去36萬年來，浮游性有孔蟲Globigerinoides ruber (G. ruber)殼體的稀土族元素對鈣之比例變化紀錄。各稀土族元素隨著時間變化有著高度的相關性，且與氧同位素數值及鎂鈣海表溫變化有著顯著的不同，顯示浮游性有孔蟲殼體內的稀土元素含量，並非受控於冰川或是溫度效應。頻譜分析顯示，所羅門海域 G. ruber 殼體內之稀土元素變化，主要因地軸傾角的41萬年週期和歲差的23萬年週期的軌道力所影響。G. ruber 殼體內錳鈣和鐵鈣對釹鈣無顯著的相關性，顯示清洗過程已排除鐵錳氧化物對稀土族元素的影響。稀土族元素分佈式顯現出所羅門海水中的稀土族元素含量，受控於當地海水以及巴布亞新幾內亞島嶼的陸源輸入。此島嶼位於間熱帶幅合區的南緣，豐沛的季節性降雨將此島充滿稀土元素的風化信號注入鄰近海域，記錄在有孔蟲殼體內，使其成為一個此島嶼的古降雨代用指標。浮游性有孔蟲G. ruber殼體的稀土族元素對鈣之變化紀錄，重現了巴布亞新幾內亞島過去4個冰期/間冰期的降雨強度變化。本研究指出，有孔蟲殼體內稀土族元素在不同地區可能代表著不同的氣候意義，可能開啟了古環境和古海洋新的研究方向。
並列摘要
Characteristics of rare earth elements (REE) have been widely used as important tracers in earth sciences. Foraminiferal test REE signatures have been suggested to reflect ambient seawater conditions and serve as valuable proxies in paleoceanography and paleoclimatogy. Here I present a past 363 kyr planktonic foraminifer Globigerinoides ruber (G. ruber) REE record from sediment core MD05-2925 (9o20.61’S, 151o27.61’E, 1661 m water depth) collected from the Solomon Sea, Papua New Guinea (PNG). High significant correlation coefficients exist for all G. ruber REE/Ca time series. This foraminiferal REE/Ca time series is different from the Mg/Ca ratio-inferred sea surface temperatures and δ18O records. This inconsistency suggests that planktonic foraminiferal REE were not directly governed by changes in ice volume or thermal condition. Solomon Sea G. ruber REE/Ca time-series was dominated by 41-kyr obliquity and 23-kyr precession periodicities. An absence of significant relation of the G. ruber Mn/Ca and Fe/Ca versus Nd/Ca indicates that Fe-Mn oxides were completely removed after a clean procedure. The REE pattern diagram expresses two dominant sources of local water masses and the input from nearby terrestrial riverine discharge. PNG located at the southern border of the Intertropical Convergence Zone (ITCZ), delivers disproportionately large amount of suspended sediment fluxes to the adjacent oceans by seasonal precipitation. The nearby marine basins as receptacles of the transported terrestrial sediments can reflect past ITCZ precipitation. This regional G. ruber REE/Ca is an island-weathering signal modulated by rainfall, related to the different insolation gradients and regional insolation. In summary, Solomon Sea G. ruber REE content is considered to be a robust paleo-precipitation proxy over the PNG. This example opens a new potential of using foraminiferal REE records as a proxy of paleoclimatogy and paleoceanography.
參考文獻
延伸閱讀
- 陸象豫、黃良鑫、傅鶴翹（2014）。蓮華池三號集水區濱水帶大氣、溪流及表層土壤溫度關係之探討。中華水土保持學報，45(4)，266-272。https://doi.org/10.29417/JCSWC.201412_45(4).0006
- 曾意翔、朱容敬（2017）。應用SuperGIS Desktop推算降雨量的三種方式－以蘭陽溪流域為例。地理資訊系統季刊，11(4)，9-11。https://doi.org/10.6628/GIS.2017.11(4).2
- 倪貞業（2012）。氣候變遷下台北地區最大三十分鐘降雨強度推估模式之建立與降雨沖蝕指數之變異點分析〔碩士論文，國立臺灣大學〕。華藝線上圖書館。https://doi.org/10.6342/NTU.2012.02810
- 傅式齊、梁守謙（2006）。Miocene Talu Sand Pinch out Study and Its Application to Hydrocarbon Potential Assessment, Western Onshore and Offshore Taiwan。石油季刊，42(2)，1-18。https://doi.org/10.30128/JP.200606.0001
- 林怡美（2001）。Late Pleistocene Environmental ChangeIndicated by Stable Isotope and Element Compositions of Bivalve Shells from Hengchun Area〔碩士論文，國立臺灣師範大學〕。華藝線上圖書館。https://www.airitilibrary.com/Article/Detail?DocID=U0021-2603200719113334