東亞地區地體構造整合研究--海峽兩岸地球科學合作計畫 (I)(II)-青藏高原東緣之新期構造活動與階地年代學研究(I)(II)

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題名:	東亞地區地體構造整合研究--海峽兩岸地球科學合作計畫 (I)(II)-青藏高原東緣之新期構造活動與階地年代學研究(I)(II) Active Tectonics and Fluvial Geochronology of the Eastern Margin of the Tibet Plateau (I)(II)
作者:	陳柔妃張國楨
貢獻者:	地質學系
日期:	2013-2014
上傳時間:	2014-02-27 13:20:02 (UTC+8)
摘要:	1999年集集大地震後，台灣不少研究學者針對西部重要的褶皺衝斷帶進行了相當多的構造地形研究，其中依據地形標記（如沖積扇，河階等）的特徵，配合其構造形態觀察到微小的地表變形。利用階地的錯位和年代的相互關係來探討構造運動，其中年代在討論構造演育上扮演關鍵的角色，影響界定斷層於百年或千年的活動速率。現今最常用的河階定年技術是 14C定年法，除了定年材料尋找不易以外亦不適用於老於五萬年所形成的階地。宇宙放射線核素定年隨著分析儀器的進步越發蓬勃發展，是一相當有發展潛力的定年技術，利用分析宇宙射線粒子撞擊地表元素產生的新元素含量來進行模擬，藉由分析 10Be、26Al的含量及兩者含量的比值變化與深度的關係（深度可逹 10-20公尺），模擬階地的曝露年代、侵蝕速度，甚至曝露歷史相關的資訊。在理想條件下，現階段可估算及運用之年代範圍在幾千年至幾百萬年之間。2008年 5月 12日中國大陸四川省汶川縣於當地時間下午 2:28，發生大規模地震(汶川大地震)，震央位於北緯 31.021°、東經 103.367°。引發地震的龍門山斷裂帶，位於青藏高原的東緣，前陸盆地的邊界。汶川大地震的發生，反應了印度－澳洲板塊與歐亞板塊間長期累積應變能的能量釋放。印度－澳洲板塊與歐亞板塊的碰撞是新生代發生的最重大的板塊運動事件，導致了青藏高原隆升、變形和地殼加厚。由於龍門山斷層帶位於山麓與平原的交界帶上，特殊的地形特徵，早已引發廣泛討論。反之在成都平原上的地質、地貌，因主為地形平坦，為晚第四紀以來之河、湖相沖積物所覆蓋，而鮮為人所注意。本研究著重於河流沖積層的地形、形貌分析，其所呈現的地質及構造特徵，為了進一步探討地形特徵形成的年代以及構造活動的速率。本研究目標之一為應用宇宙放射性核素定年法於階地的出露年代，進而在不同時間尺度下探討區域的抬升與下切速率；其二為得到詳細的地貌量化和時間控制，進而重構四川盆地前緣褶皺逆衝帶之地貌與構造演育。 After the 1999 Chichi Earthquake, several active structures are well study at the fold-and-thrust belt in western Taiwan. Some of these morphological marks (e.g. alluvial fan, river terrace, etc.) and tectonic characteristics have been observed from the surface deformation. Combined to the tectonic offsets, the chronological framework of emplacement and abandonment of these geomorphic markers is thus a fundamental data to determine fault slip-rates integrated over several tens to several hundreds of thousands years. But, alluvial material younger than 50 ky old could be dated through radiocarbon method the datable material is generally poorly preserved due to the weathering context. To achieve these scientific goals, the analysis should combine both the quantitative geomorphology and the statistical curve fitting from the cosmogenic nuclides concentration (10Be, 26Al) measured in alluvial terraces profile. Accurate dating requires both the quantities of the post-depositional production of 26Al and 10Be, and the sampling depths could be up to 10-20 meters. By using the cosmogenic radionuclide concentration at depth profile, the method deduces both the inheritance and the deposition age of the surface. On 12 May 2008, the devastating magnitude 8.1 (Wenchuan) earthquakes struck the eastern edge of the Tibetan plateau, collapsing buildings and killing thousands in major cities aligned along the western Sichuan basin in China. The surface rupture zone generated by the Wenchuan earthquake and aftershocks are distributed along the NE-trending Longmenshan tectonics belt. The Sichuan basin, the flat area (Chendu plane) is dense population and heavy of industry, the tectonics activity and geological hazard within this area basin becomes a major concerns. This project is organized around methodological and thematic tasks aiming at characterizing deformation behaviour of different morphostructural units, activity changes along fault and landscape evolution. Within the highly active context of the western Taiwan, this project objectives are quantifying the uplift/incision rates at different time scales using in situ-produced cosmogenic nuclides in river-borne sediments and alluvial terrace deposits), and (2) reconstructing the tectonic and landscape evolution of the fold-and-thrust belt, detailed geomorphic quantification and time controls will be obtained using cosmogenic radionuclides dating.
顯示於類別:	[地質系] 研究計畫

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