應用高解析度數值地形模型精進輕度變質岩區地質圖-以頭城地質圖幅為例

地質圖與區域地質剖面為了解區域地質架構的重要基礎資料，然而陡峭地形、濃密植被等因素限制了地質調查時在野外直接量測的地質證據。臺灣相關部門自2005年以來開始以光達測繪獲得高解析度數值地形模型已逐漸完備，電腦軟體三維環境顯示與編修技術逐漸成熟，前人研究在臺灣西部麓山帶以光達精進地質圖已獲良好結果，本研究在前述基礎上，於頭城地質圖幅內，對雪山山脈漸新世至中新世輕度變質岩地層，以室內地形學判釋與野外查核，並參考前人於此地區之研究，進行地質製圖。判釋過程中，我們以高解析度地形與其衍生之陰影圖、坡度圖等於軟體三維環境下，觀察不同光源、視角下地形特徵，進行層理面之判釋，並根據繪圖尺度由大而小標示區域參考線、層理特徵線，最後是斷層系統。過程中以自製之可程式化人機介面裝置－連點君輔助製圖，可大幅提昇標記密度與製圖效率。根據標記得出的兩千六百餘條層理特徵線與野外查核資料，本研究繪製頭城圖幅五萬分之一地質圖一張，區域構造為一北陡南緩之鶯仔瀨向斜，斷層系統則有區分西部麓山帶地層與雪山山脈地層之屈尺斷層、重新定位後金瓜寮斷層與三叉坑斷層、枋腳斷層重新解釋為切穿鶯仔瀨向斜軸部之背衝斷層、研究區域南側提出大金面山正斷層系統，分為蕃薯寮、外澳-福德坑、四堵-石牌-金面山等三大區塊。本研究成功克服上述不利於傳統地質工作的限制，為難以抵達的區域獲得了更詳細的地質證據與區域構造解釋，提供未來地質研究等各項用途的重要參考資料。

關鍵字

三維地質製圖；地質圖；高解析度數值地形；頭城；雪山山脈；變質岩區

並列摘要

Geologic map and regional geologic cross-section are the important base map to understand the local geologic conditions. In the past, however, geologists could collect very limited field data due to the heavy vegetation, steep terrain, human activity, etc. The previous studies used LiDAR-based high-resolution DEM to interpret geomorphic features and improved the geologic map in the fold and thrust belts in northern Taiwan. In this study, we focus on the low-grade metamorphism area in Toucheng, northern Taiwan. The age of the formations is from Oligocene to Miocene and lithology contains quartzite, argillite, shale, sandstone and their alternations. We overlay the pseudocolored DEM, hillshade and slope layers in the 3D GIS environment, where we can not only adjust view angle and illumination but also mark geomorphic features directly. In the mapping stage, a custom-built human interface device, Liandianjun, can improve the mapping efficiency. We first identify the regional structure reference lines and then map the feature lines of bedding carefully. Finally, fault lineaments are determined based on the different attitudes between the two walls. With 2600 feature lines of bedding and field verification, we finish the 1:50000 Toucheng geologic map. One fold and five major faults are in the study area. Yingzilai syncline is an asymmetric fold where beddings in the north are steeper than the south ones. The location of Jingualiao fault and Sanchakeng are modified based on geomorphic evidence. Fangjiao fault is reinterpreted as a back-thrust fault that cut the north limb of Yingzilai syncline. The Dajinmianshan normal fault system is introduced for the first time in the southern study area. It can be further divided into three regions: Fanshuliao region, Wai’ao-Fudekeng region and Sidu-Shipai- Jinmianshan region. We have successfully concurred the difficulties of the traditional geologic mapping work and provided detailed geologic information in the metamorphic area. The map can be used as the base map of future research in this area.

並列關鍵字

Geologic map ； Geomorphic mapping in 3D environment ； Hsuehshan Range ； High-resolution digital elevation model ； Metamorphism rock ； Toucheng

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應用高解析度數值地形模型精進輕度變質岩區地質圖-以頭城地質圖幅為例

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