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題名 | 礫石粒徑與海水面變化之關係--以屏東沖積扇群為例=Can the Size of Fluvial Gravels Record Change of Sea Level? An Example from Alluvial Fans in Pingtung, Taiwan |
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作者 | 陳文福; 江崇榮; | 書刊名 | 經濟部中央地質調查所彙刊 |
卷期 | 12 1999.06[民88.06] |
頁次 | 頁25-38 |
分類號 | 358.51 |
關鍵詞 | 礫石最大粒徑; 海水面變化; 末次冰期; 沖積扇; 屏東平原; Maximum gravel size; Sea level change; Last glacial; Alluvial fans; Pingtung; |
語文 | 中文(Chinese) |
中文摘要 | 本文研究屏東平原沖積扇群之礫石地層,研究最大礫石粒徑變化並與南側砂泥地 層對比,探討與海水面變化之關係。前人研究指出河流沉積層序受到氣候、構造、沉積物供 應量與海水面變化等因素影響,但是如何在地層記錄中辨別何者為主因爭議仍大。本研究以 臺灣南部屏東平原之沖積扇以五站探井作為材料。其中繁華、彭厝、前進等探井位於隘寮沖 積扇, 關福探井位於口社沖積扇,赤山探井位於萬安、泰武沖積扇之間,探井深度為 250m ,沉積年代約在六萬年內。以衝鑽法施工使用抽泥筒將礫石夾起,每公尺選取最大礫石一顆 ,量取三軸,並計算其理論體積,五探井之最大礫石共有 1030 顆。分析結果顯示繁華、彭 厝、前進、赤山等探井礫石之最大粒徑在井下 70 - 100m 之間。 地層可分為三段,與南邊 的地層比對, 發現第二段可與海進期 (約 17 - 6kyBP) 對比,礫石體積往上有漸漸變小的 趨勢。 第一段可與全新世海水面停滯期對比 (約 6kyBP 至今 ),礫石最大粒徑並沒有向上 變大的趨勢。第三段可與末次冰期地層對比,繁華井有明顯之向上變粗現象。第三段與第二 段的界面礫石最大,解釋為海退時造成之層序界面,此時關福井為河道外環境發育古土壤。 繁華井位於彭厝井上游,第一、二段之粒徑皆大於彭厝井,但第三段卻相反,位於下游之彭 厝井卻大於位於上游的繁華井,顯示第三段之沖積扇系統與現今不同,推測末次冰期時彭厝 井位於繁華之上游,河流應由北往南流,而非今日之由東往西流。 |
英文摘要 | The purpose of this paper is to study the maximum gravel size variation of alluvial fans in Pingtung, southern Taiwan, and to interpret the trend in variation from the viewpoint of sea level change. Previous studies have pointed out that fluvial strata are influenced by climate, tectonism, sediment supply, and sea level change. However, how to recognize the major control factor in rock records is still a controversy. In this study we took gravels from five 250m deep borehole on alluvial fans. The sedimentary age of the upper 250m ranged from 60kyBP to the present. The three axes of the maximum gravels were measured and the ideal ellipsoid volume of gravels were calculated at one meter intervals. In total 1030 maximum gravels were sampled and analyzed. The data show three distinct layers of maximum gravel size could be correlated with strata in the south. The largest size of maximum gravel is located below 70-100m in wells FH, PC, CC and CS. The maximum gravel size of the middle layer B is fining upward and is correlated with the 17-6kyBP transgression. The maximum gravel size of the upper layer A is correlated with the highstand progradation sequence from 6kyBP untill present, but it doesn't show the increase in gravel size upward trend. The lower layer C was deposits from the Last Glacial and doesn't show a unique trend. A sequence boundary in these gravel beds is suggested at the boundary between the layer B and C,which has the largest sized gravel. In well KF, a 2m thick paleosol layer is found and is correlated with the sequence boundary. In layers A and B the maximum gravel size of well FH is larger than weli PC. This is reasonable because well FH is upstream from well PC and the river flows from east to west. A different river system possibly flowed from north to south, and is indicated in layer C because the maximum gravel size of weli FH was smaller than in well PC. |
本系統之摘要資訊系依該期刊論文摘要之資訊為主。