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標題: | 末次最大冰期以來臺灣北部前陸盆地與張裂盆地的構造與壓密特性 The tectonic and compaction rates of extensional and foreland basins in the northern Taiwan since the Last Glacial Maximum |
作者: | Wen-Hsiang Chiu 邱文翔 |
指導教授: | 陳文山(Wen-Shan Chen) |
關鍵字: | 北臺灣,壓密作用,垂直變動速率,活動斷層, the northern Taiwan,compaction,tectonic rate,active fault, |
出版年 : | 2019 |
學位: | 碩士 |
摘要: | 垂直變動速率是指示某區域在特定時間範圍由構造作用造成固結基盤抬升或是沉降的速率,通常透過沉積物的垂直位移估算來獲得。堆積厚層鬆散未固結沉積物的地區,在沉積物壓密作用發生後造成地層厚度減少並使沉積物產生沉降,導致錯估垂直變動速率。末次最大冰期(Last Glacial Maximum,LGM: <18 kyr)以來,北臺灣的前陸盆地及張裂盆地曾經被海水覆蓋而堆積大量未固結沉積物。因此,本研究透過假設在淺層的地層壓密作用符合單向度壓密原理,利用壓密路徑回推各層的壓密量。蒐集北臺灣共134口鑽井資料以及403筆定年數據,以沉積環境、古海水面、樣本年代及估算的壓密量,獲得更精確的垂直變動速率,探討自末次最大冰期以來北臺灣各地區的構造變形特性。
由於位處於不同的大地構造環境,本研究將北臺灣分為三個地質構造區。(一)後拉張環境產生的北部與東北部張裂盆地,包含以礁溪斷層以南至冬山斷層之間的蘭陽盆地(垂直變動速率:-17.5~0.0 mm/yr),以及山腳斷層以東的臺北盆地(垂直變動速率:-2.3~0.8 mm/yr)及金山盆地(垂直變動速率:-0.7~0.7 mm/yr)。(二)碰撞時期由逆衝斷層組成的西北部外麓山帶,包含於湖口斷層以南至新竹斷層之間的新竹地區(垂直變動速率:-1.3~1.5 mm/yr),以及新竹斷層以南至龍港斷層(後龍斷層)之間的竹南地區(0.1 mm/yr)。(三)前緣逆衝斷層下盤的西部與西南部前陸盆地,包含臺中-彰化海岸平原(垂直變動速率:-3.5~2.9 mm/yr)以及雲林-嘉義地區(垂直變動速率:-4.3~3.6 mm/yr)。 透過鑽井以及斷層的垂直錯移速率得知,蘭陽盆地全區為沉降環境,礁溪斷層(垂直錯移速率:-2.0 mm/yr,推測東側更快)及濁水斷層(垂直錯移速率由西向東遞減:-3.1 ~-9.4 mm/yr),其間的三角區域為沉降盆地;金山盆地西側緩慢沉降,向東南轉為緩慢抬升;臺北盆地呈現西北側沉降較快向東南側轉為不太變動,接近山腳斷層(垂直錯移速率:-2.0~-1.5 mm/yr)處為沉降中心,顯示其活動導致盆地西側的陷落;新竹地區大致為極緩慢抬升的環境,末次最大冰期以來湖口斷層(垂直錯移速率:>0.0 mm/yr)與新竹斷層(垂直錯移速率:>0.8 mm/yr)垂直方向的變動較不明顯;竹南地區呈現緩慢抬升,因為資料少僅能得知斗煥坪斷層以及龍港斷層南側區域抬升較北側快;臺中-彰化海岸平原呈現西側沉降東側抬升,東側可能為大甲斷層(垂直錯移速率:>0.8 mm/yr)以及彰化斷層(垂直錯移速率:4.3 mm/yr)在淺層產生塑性三角剪切帶造成的抬升;雲林-嘉義地區亦呈現西側沉降東側抬升,東側可能為桐樹湖斷層以及嘉義斷層(垂直錯移速率:3.1 mm/yr)在淺層產生三角剪切帶造成變形而抬升;在最南側的梅山斷層(垂直錯移速率:2.5~0.4 mm/yr)垂直錯移速率由東向西遞減,變形模式顯示其應具有逆衝分量。 沉積物壓密量對於長期垂直變動速率在蘭陽盆地、臺北盆地、臺中-彰化海岸平原以及雲林-嘉義地區等沉積物堆積較厚的區域影響較明顯,而在沉積物較薄的金山地區及桃竹苗沿海區域壓密量較少。壓密作用的影響大小主要取決於該區域的未固結沉積物厚度。 The purpose of the study is to understand the tectonic rates of the extensional and foreland basins in the northern Taiwan. In this thesis, the tectonic rate represents the variation of elevation in the vertical direction over specific time interval induced by tectonic movement, and could be estimated by calculating the vertical displacement of the sediments. However, in the basins where thick, uncompact sediments overlying the basement, the vertical displacement of the sediments is often underestimated or overestimated because of the subsidence caused by the compaction of sediment itself as the water goes out of the pore, leading to the miscalculating of tectonic rates. In the northern Taiwan, thick, uncompact sediments were deposited in the extensional and foreland basins since Last Glacial Maximun (LGM: <18 kyr). This study assumes that the sediment compaction follows the Terzaghi's principle and estimate the amount of compaction by one-dimensional compression path. We combined 403 14C dating data over 134 boreholes, trying to figure out more accurate tectonic rates in order to explain the tectonic pattern in the northern Taiwan since LGM. According to different tectonic settings, we separated basins in northern Taiwan into three groups. For the extensional basins produced by post-collisional extension in northern and northeastern Taiwan, the tectonic rates of the Lanyang Plain decreased from 0.0 mm/yr at the edge of the basin to -17.5 mm/yr in the basin depocenter; the tectonic rates of the Taipei Basin decreased from 0.8 mm/yr in the east to -2.3 mm/yr in the west; the tectonic rates of the Jinshan Plain decreased from 0.7 mm/yr in the east to -0.7 mm/yr in the west. For the outer Range produced by collision and compression of fold and thrust belt in northwestern Taiwan, the tectonic rates of the Hsinchu Coastal Plain is about 1.5~-1.3 mm/yr, and 0.1 mm/yr in the Chunan Coastal Plain. For the foreland basins of the footwall of frontal faults in western and southwestern Taiwan, the tectonic rates of the Taichung-Changhua Coastal Plain decreased from 2.9 mm/yr in the northeast to -3.5 mm/yr in the southwest; and decreased from 3.6 mm/yr in the east to -4.3 in the west in Yunlin-Chiayi-Tainan Coastal Plain. To compare how much amount of long-term uplift rates were affect by the compaction in each region, basins with thick sediments such as the Lanyang Plain, the Taipei Basin, the Taichung-Changhua Coastal Plain and the northern Yunlin-Chiayi-Tainan Coastal Plain obviously sustained more sediment compaction, thus more miscalculating of the tectonic rates than basins with less sediments, including the Jinshan Plain, the Hsinchu Coastal Plain, and the Chunan Coastal Plain. These implies that thickness of sediments could be the main factor that influences the compaction of sediments. In basins with thick sediments, compaction cannot be ignored. Furthermore, the data shows that the position of the sample and the thickness of sediment are significant factors of compaction. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/74015 |
DOI: | 10.6342/NTU201901069 |
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顯示於系所單位: | 地質科學系 |
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