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題名 | 從構造地形探討嘉南地區活動構造及構造分區=Tectono-Geomorphologic Studies in the Chiayi-Tainan Region in Southwestern Taiwan and its Implications for Active Structure |
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作者 | 陳文山; 楊志成; 楊小青; 吳樂群; 林啟文; 張徽正; 石瑞銓; 林偉雄; 李元希; 石同生; 盧詩丁; | 書刊名 | 經濟部中央地質調查所彙刊 |
卷期 | 17 2004.09[民93.09] |
頁次 | 頁53-77 |
分類號 | 356.232 |
關鍵詞 | 構造地形; 褶皺-逆衝斷層帶; 平移斷層; 古坑斷層; 新化斷層; Meandering river; Strike-slip fault; Terrace; Active fault; |
語文 | 中文(Chinese) |
中文摘要 | 嘉南地區是臺灣島地殼變動最活躍區域之一。本研究依據麓山帶至海岸平原的構造地形特徵劃分為三個構造地形區:分別為麓山帶、隆起臺地與海岸平原區。本研究由河流地形型態以及綜合前人針對井下岩心層序比對、河階定年(長期變動速率)、大地測量(短期變動速率)等方法計算三個地形構造區水平與垂直的地殼變動速率分別如下,麓山帶構造地形區平均每年抬升速率為7-5公厘,向西水平移動速率約55-15公厘。隆起臺地構造地形區平均每年抬升速率為4.4-0.5公厘,向西水平移動速率約20-10公厘。海岸平原構造區屬於前陸盆地的下陷環境,平均每年沉陷速率為11-1公厘,向西水平移動速率約10-5公厘。另由嘉南海岸平原的沉降速率又可以劃分為兩個沉降速率不同的區域,一位於八掌溪流域以北,平均每年沉降速率為2.2-1公厘;另一八掌溪流域以南至鹽水溪以北區域平均每年沉降速率為11-5公厘,此區域的沉降速率遠大於八掌溪以北區域,而鹽水溪以南區域屬於麓山帶與隆起臺地構造地形區的抬升環境。嘉南海岸平原區不等量沉降因素是受控於沿著八掌溪及鹽水溪流域發育的東西向平移斷層。 褶皺-逆衝斷層帶沿著數公里深的脫底斷層向西逆衝,淺處岩層褶皺變形經常受制於盆地深部的構造。尤其約呈東西走向的正斷層構造經常受近期的擠壓而再度活躍,轉變以橫移作用為主的平移斷層。因此,臺灣西南部褶皺-逆衝斷層帶經常被東北走向的平移斷層分割,形成數個獨自活動的構造塊體。本研究依據晚更新世以來的地形、構造特性以及從長期與短期的地殼變動速率,將西南部地區劃分為四個構造區塊如下,臺中、嘉義、臺南與高雄;各區塊大都以西南或西北走向的平移斷層為界;古坑斷層、義竹斷層與新化斷層即為上述構造區塊的主要分界。 |
英文摘要 | We analyze geomorphic evidence of Holocene crustal deformation in the Chiayi-Tainan region which has the most active fold-thrust belt in Taiwan. Based on the geomorphic characteristics, the region can be divided into three geomorphic terrains, namely the foothills, uplifting-terrain, and the coastal plain. The Mujiliao and Liuchia Faults, which mark the western edge of the foothills, are the most active deformation fronts. The foothills, however, are more complex, with several thrust faults assumed to be merging with a decollement at depth. The uplifting-terrain shows a gently inclined surface where a meandering river incises the warped topography. It is inferred that the topographic expression is a blind thrust under an uplifting-terrain which marks the frontal thrust of the fold-thrust belt in southwestern Taiwan. The coastal plain, which formed in front of the uplifting terrain, represents a subsided foreland basin where meandering channels flow onto a very flat coastal plain. To derive the uplift rate from the geodetic data, dated fluvial terraces, and from core sediments, we obtained an average uplifted rate of 7-5 mm/yr for the foothills and, 4.4-0.5 mm/yr for the uplifted terrain, and the average subsided rate of 11-1 mm/yr of the coastal plain. The horizontal displacements recorded from the GPS observations show a western movement of about 55-15 mm/yr in the foothills, 20-10 mm/yr in the uplifted terrain, and 10-5 mm/yr in the coastal plain. Estimate of the shorting rate are about 10-5 mm/yr between the coastal plain and the uplifted terrain and about 30-10 mm/yr between the uplifted terrain and the foothills. Geomorphic evidence indicated that active tectonics in the southwestern fold-thrust belt appear to have been concentrated between the foothills and the coastal plain since the Holocene period. The belt can be divided into 4 block domains: the Taichung, Chiayi, Tainan, and Gaoping domains separated by several strike-slip faults including the Gukeng, Chuji, and Hsinhua Faults. |
本系統之摘要資訊系依該期刊論文摘要之資訊為主。