台灣西北部海岸階地的地形學研究

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Title:	台灣西北部海岸階地的地形學研究 A Geomorphology Study of Marine Terraces on Northwestern Taiwan
Authors:	劉佳怡
Contributors:	地學研究所
Keywords:	海階海準變動地殼變動地盤隆升率地形學海岸台灣
Date:	2006
Issue Date:	2014-08-26 13:57:51 (UTC+8)
Abstract:	海岸階地（海階）的形成通常是海準面變動、地殼變動或兩者共同作用之結果。因此，研究海階不僅可印證推論古氣候、往昔海準面變化及地殼變動狀況，更可藉以了解各區域間變動的差異，全盤了解大地構造的意義，而且小規模的海階變動，時常與地震活動伴生，因此，研究海階更可作為判讀地震週期的依據之一，所以，世界各地位於地殼活動帶的國家對於海階的型態與演育過程均作詳細的調查及研究。本論文以淡水河以南至大安溪以北之海階作為研究範圍，利用室內航空照片、1: 5,000像片基本圖判讀、野外實察與室內資料分析等方法，發現台灣西北部位於觀音山北部沿海、新竹山子頂沿海、客雅溪口南岸、後龍溪口南岸等四個地區，都有零星的海階分布。經過階地分布、地形特徵與階序對比，並利用世界海階對比基圖求出該地區的地殼隆升率與海階可能形成的年代，藉以了解各區域間變動的差異。經研究發現，台灣西北部海岸地區的海階大致上可劃分為高位及低位兩群階地，高位海階分布的高度在15-275m之間，階面覆蓋著紅壤層，為晚更新世時所造成；低位海階分布的範圍與高度較小，在海灘與高位階地末端階崖之間，沿著海岸成帶狀分布，階面無紅壤掩覆，海拔高度大多在10m以下。低位海階構成的物質多以礫石及砂為主，屬全新世海階，即第四紀最後一次冰期結束後，近一萬年以來全球高海水位時期所形成。利用修正之世界海階對比基圖與已有的定年資料，輔以地形地貌及堆積物特徵比較，獲得各段階地之平均隆升率，觀音山北部沿海、客雅溪口南岸、後龍溪口南岸三個地區，經過比對，分別是2.1mm/y、2.2mm/y、2.15mm/y，數值相近，顯示本該區之地盤隆升率及海準變動狀況大致相同；僅新竹山子頂沿海地盤隆升率較小，為1.4mm/y。新竹山子頂之隆升率較小，應是受到新竹凹陷構造區之影響。 Marine terraces are influenced by eustatic changes , tectonic movement . Therefore, there are considered as indicators of a regional tectonic , paleo-climate & sea-level variation and crust movement . From Tamsui river to Ta,an river , the study area is divided four groups , use the methods of aerial photographic interpretation, field survey and data analysis , some conclusions are inferred as following： 1)Classified and correlated by continuity of altitude and extension of terrace surface , there are two type of marine terraces in the study area . One is Pleistocene terraces , their height is distributed from 15-275m and covered with thick laterite . The other one belongs to Holocene terraces , which height mostly below 10m , developed along the coastal lowland and consisted of sand and gravels . 2) Based on dating , elevation , mode of erosion and deposits feature of terraces, the marine terraces uplift rate of Northwestern Taiwan can reflect regional tectonic activities and sea level variation . The marine terraces of uplift rate on Shinchu coast is 1.4mm/y , and the uplift rates on north coast of Kuanyin Volcano , south coast of Keya river estuary and south coast of Holung river estuary are 2.1mm/y , 2.2mm/y and 2.15mm/y . The uplift rate on Shihchu coast is smallest on Northwestern Taiwan , the area are influenced by Shinchu Subsidence area .
Appears in Collections:	[Department of Geography & Graduate Institute of Earth Science / Geography ] thesis

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