8000年來蘭陽地區之環境變遷

Please use this identifier to cite or link to this item: http://ntour.ntou.edu.tw:8080/ir/handle/987654321/29917

Title:	8000年來蘭陽地區之環境變遷 Enviromental Changes in Ilan Region Since 8 Ka, Taiwan
Authors:	Shie-Ying Wen 溫謝穎
Contributors:	NTOU:Institute of Applied Geosciences 國立臺灣海洋大學:應用地球科學研究所
Keywords:	宜蘭;化學風化;颱風;季風;鉀銣比 Ilan;Chemical Weathering;Typhoon;Monsoon;K/Rb
Date:	2011
Issue Date:	2011-11-23T03:23:34Z
Abstract:	本研究取自宜蘭大湖之湖泊沉積物岩芯 (DH-7B)，並利用X光粉末繞射分析、感應耦合電漿質譜分析和雷射粒徑分析方法，鑑定礦物之半定量、主要元素和微量元素結果。藉由礦物含量與化學特性之變化，比對梅花湖岩芯資料，可比較沉積物的來源與化學風化指標，並進一步探討宜蘭地區過去的古氣候與古環境變遷之歷程。本湖泊岩芯涵蓋過去約7500年之記錄。比對蘭陽溪圍岩露頭之礦物半定量資料，顯示在 6100~5100 yr BP以及 4300~3800 yr BP這二個時期的伊來石及白雲母含量增加，係高海水位造成蘭陽溪氾濫入大湖的主要時期，與梅花湖 3700 yr BP以前受高海水位影響造成羅東溪氾濫之結果相符。化學分析資料則顯示 1650~1250 yr BP以及 1100~400 yr BP這二個時期 K/Rb 比值變高、化學風化增強，前者係因颱風頻繁導致降水增加，後者與梅花湖之高化學風化時期吻合( 1100~700 yr BP)，顯示在中世紀暖期東北季風增強與颱風雙重影響之共伴效應造成整個蘭陽平原降雨更為可觀。 400 yr BP至今大湖中石英含量幾乎達到頂峰，同時期梅花湖石英含量亦有增加，顯示此時期蘭陽平原可能受小冰期影響，氣候呈現冷乾的型態。綜合蘭陽溪沖積扇資料、孢粉資料、氣象資料、梅花湖與大湖之化學指標以及粒徑分析結果，推測在 2100~1500 yr BP期間，構造活動事件造成邊坡不穩定，促使大規模的河階地與河道堆積物生成。 1600 yr BP以後開始降雨量增加，大量的降雨順勢將崩積物帶往下游地區，赤楊花粉記錄在此時亦達最高峰。 1500~1300 yr BP期間梅花湖與大湖同時出現粒徑變粗的訊號，更顯示此時期降雨的頻繁。 2100~1300 yr BP 期間蘭陽平原經歷了連續的災難，也印證了宜蘭地區考古記錄中所記載的文化斷層為何發生在 2400~1300 yr BP。 This core was taken from the Da-Hu Lake (DH-7B) Ilan, Taiwan for particle size, mineral, and element content analyses. The study provides an explanation of core data found in DH-7B through comparison of mineral and geochemical content by geochemical proxy and sediment source to explore the paleoclimatic conditions and paleoenvironmental change in Ilan. The sedimentary core provides a 7,500 year record of the Da-Hu Lake including: Lan-Yang River flooding between 6100~5100 yr B.P. and 4300~4800 yr B.P., frequent typhoon activity leading to increased precipitation between 1650~1250 yr B.P., and wetter periods between 1100~400 yr B.P. in Ilan that may indicate strengthening in both typhoon and winter monsoon activity. Quartz records indicate that the eastern monsoon had a profound effect in the Ilan region during the little ice age 400 years ago. Based on the upper reaches of the Lang-Yang River having extensive fan-terracing, as well as pollen sequences, meteorological data, particle size analysis, and chemical indicators in the Da-Hu and Mei-Hwa Lake, it is speculated that for the period 2100 ~ 1500 yr B.P. large-scale river deposits occurred in Da-Hu lake because of slope instability caused by tectonic activity. In addition, a maximum amount of Alnus pollen also occurred in 1600yr B.P. This pollen could have been carried along with other colluvium down the Lang-Yang River as a result of torrential rains from monsoon and typhoon activity. Presently the core records fdisplay the Ilan region experienced successional catastrophes during 2100~1300 yr BP. It also proves that archeological hiatus occurred during 2400~1300 yr B.P.
URI:	http://ethesys.lib.ntou.edu.tw/cdrfb3/record/#G0M97860011 http://ntour.ntou.edu.tw/handle/987654321/29917
Appears in Collections:	[應用地球科學研究所] 博碩士論文

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