頁籤選單縮合
題 名 | Magnetic Analysis on Lacustrine Deposits of Yuan-Yang Lake, Northern Taiwan=臺灣北部鴛鴦湖湖積物之磁學特性分析 |
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作 者 | 李德貴; 林華松; 劉平妹; | 書刊名 | 中國地質學會會刊 |
卷 期 | 41:1 1998.02[民87.02] |
頁 次 | 頁143-158 |
分類號 | 351.983 |
關鍵詞 | 磁化率; 湖積物; 環境變遷; Magnetic susceptibility; Lacustrine sediment; Environmental change; |
語 文 | 英文(English) |
中文摘要 | 本文將研究兩根鑽取自臺灣北部鴛鴦湖湖積物之岩芯(#YYL2和#YYL6)的磁學特 性,並進而探討它們所表示之環境變遷意義。共有超過300個樣本被分析。 碳十四定年結果指出,岩芯#YYL2底部修正過之年代約為距今4,000年前,而岩芯#YYL6 之年代則約為距今4,500年前。兩根岩芯之古地磁場長期變化型態的比較,以及和兵頭等人 (1993)整理來自日本的海洋知湖泊沉積物古地磁場長期變化結果之比較,也確認此結果。根 據定年資料估計鴛鴦湖湖積物之沉積速率約為每年1公厘。 本研究發現兩根岩芯之磁化率變化型態十分不同,岩芯#YYL2顯現比岩芯#YYL6高相當 多之磁化率,此差異現象之發生可能與岩芯位址及岩芯內含主要磁性礦物息息相關。因為岩 芯#YYL6比岩芯#YYL2靠近湖岸,但較遠離岩石碎屑之物源,同時因較淺而可能有較弱之逕 流之搬運力,使得岩芯#YYL6接受較少之岩石碎屑源,但反而有較多之,因而降低了磁化率。 此外,具有較多有機植物碎屑源之岩樣所含的主要磁性礦物為鈦鐵礦而非磁鐵礦,這可能是 造成兩根岩芯極大磁化率差異的另一主要因素。 在岩芯#YYL2中顯現多處超高值之磁化率異常,它們之沉積物主要為青灰色之岩屑而非 有機的植物碎屑,這些沉積物層被認為含較多磁性礦物,而其物源則被認為來自周圍岩層之 風化作用,在時此現象更為顯著。若依每年 |
英文摘要 | This study presents the results about the magnetic properties of two lacustrine sediment cores (#YYL2 and #YYL6) sampled from Yuan-Yang Lake in northern Taiwan and discusses their environmental implications. More than 300 specimens from these two cores were analyzed. Results of □C dating indicate that the calibrated age at the bottom of the core #YYL2 is about 4,000 cal.B.P. and that of the core #YYL6 is about 4,500 cal.B.P. Both of them seem quite reasonable when we compare the paleomagnetic secular variation patterns of the studied cores with those of marine and lake sediments from Japan compiled by Hyodo et al (1993). They further enable us to estimate the sedimentation rate of Yuan-Yang Lake as about 1 mm/yr. Different variation patterns of magnetic susceptibility of the two studied cores have been found. Core #YYL2 shows relatively higher value than that of core #YYL6. This phenomenon is thought to be mainly due to the geographic conditions of the coring sites and to the magnetic mineral contained. Site #YYL6 is located closer to the lake flank but farther away from the source of clastic sediments than site #YYL2. Furthermore, the former is in a shallower water depth with weaker inflow force than the latter. With less clastic debris and more organic materials, therefore, core #YYL6 naturally has weaker magnetic susceptibility signals. Actually, samples with more organic materials are apt to be dominated by ilmenite instead of magnetite as their major magnetic carrier. Several high peaks of magnetic susceptibility appear in the layers of core #YYL2 dominated by green-gray sediments instead of organic materials. It is related to the fact that these layers contain much more magnetic minerals. Most of the sediments of these layers |
本系統中英文摘要資訊取自各篇刊載內容。