沉降環境的山麓河谷地形特性--探討臺北盆地、蘭陽平原與屏東平原鄰近山麓地形與構造的關係

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题名:	沉降環境的山麓河谷地形特性--探討臺北盆地、蘭陽平原與屏東平原鄰近山麓地形與構造的關係 Geomorphic Characteristics of the Mountain-Valley in the Subsidence Environment of the Taipei Basin, Lanyang Plain and Pingtung Plain
作者:	陳文山楊志成吳樂群楊小青陳勇全顏一勤林啟文張徽正石瑞銓林偉雄劉立豪黃能偉
贡献者:	地質所
关键词:	臺北盆地蘭陽平原屏東平原山腳斷層潮州斷層 Taipei basin Lanyang plain Pingtung plain Shanchiao fault Geomorphology
日期:	2004-09
上传时间:	2016-07-07 10:30:35 (UTC+8)
摘要:	臺灣正處於晚新生代褶皺造山帶環境，隆起地區山脈的河谷都呈現V型谷，但是部分地區處於沉降環境的山麓河谷卻呈現堆積型態的U型谷。堆積型河谷主要的特徵是埋積厚層沉積物，河谷橫剖面呈寬平的U型谷，因大量沉積物埋積作用造成河谷中或山麓前緣經常呈現孤立於寬平谷中的獨立山地形。從河谷地形來看，屬於堆積型河谷的區域有臺北盆地與蘭陽平原周圍的山麓河谷以及屏東平原東側中央山脈前緣的河谷。堆積型河谷的形成決定於沉積速率與沉降速率，沉積速率大於沉降速率就會形成堆積型河谷；反之，則在盆地周圍形成侵蝕型的山麓河谷。另外，山麓前緣邊界的彎曲度也可以反應此種關係，當盆地沉降速率大於沉積速率時，會明顯呈現山前斷層崖地形，崖線彎曲度值約接近1，如臺北盆地西側邊界的山腳斷層崖，呈現直線型斷層崖。這種環境下的河寬與山高比率（R）一般都在0.5以上，甚至遠大於1.0。但是，當沉積速率大於沉降速率時，沉積物堆積超覆斷層帶時，造成山前崖線的彎曲度變大，崖線彎曲度值都大於2，且山麓河谷呈現堆積型的U型谷，河寬與山高比率大都小於0.5，甚至小於0.1，如蘭陽平原南北兩側的山麓前緣邊界。 The Taiwan orogenic belt related to the ongoing arc-continent collision has been an active tectonic environment throught the late Quanternary. Whereas the geomorphologic characters, such as shapes of mountain valley, depends strongly on the tectonic activity. Therefore, subsidence mountain tends to result in a U-shaped of depositional valley characterized by broadly flat valley-floor and lower relief (lower valley-floor width-to-height ratio), lower stream-gradient, isolated mound within fluvial and alluvial plain, and thick-bedded fluvial deposits within the mountain valley. The depositional mountain-valley can be observed in the vicinity of the Taipei Basin, the Lanyang Plain, and the eastern part of the Pingtung Plain where the geomorphic featrues commonly response to a tectonically subsidence environment. Sinuousity of mountain fronts has been also used to delineate the tectonic activity, and the distribution of mountain fronts is associated with the depositional and subsidence rates. If the rate of deposition less than subsidence, the ground surface will display a linear mountain-front, such as fault scarp of the Shanchiao Fault and the western boundary of the Pingtung Plain. On the other hand, it shows an embayment of mountain-front creating higher sinuousity, such as the vicinity of the Taipei Basin, the Lanyang Plain, and the eastern boundary of the Pingtung Plain.
關聯:	經濟部中央地質調查所彙刊 17 民93.09 頁79-106
显示于类别:	[地質系] 期刊論文

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