應用空載光達數值地形精進火成岩與沉積岩混合區地質圖：以海岸山脈地區玉里地質圖幅為例

Using airborne LiDAR-derived DEM to improve the geologic map in igneous and sedimentary rock terrains: a case study of the Yuli map in the Coastal Range

趙柏濂(Po-Lien Chao)

指導教授 ： 詹瑜璋

共同指導教授 ： 胡植慶(Jyr-Ching Hu)

國立臺灣大學/理學院/地質科學研究所/碩士(2021年)

https://doi.org/10.6342/NTU202101583

摘要

過去繪製二維地質圖時，受限於台灣植被茂密與地形陡峭，在野外露頭能取得的資料有限，因此難以提高地質圖製圖解析度。近年來，光達技術產製的數值高程模型，已濾除覆蓋地表的植被，展示精細裸露地形，而廣泛應用於斷層、山崩、地質製圖等分析。前人研究證實在沉積岩與輕度變質岩地區，運用高精度與高解析度的數值地形，判釋層面與構造的地形特徵，具精進地質圖的潛力。本研究將以海岸山脈地區玉里地質圖幅為例，進一步討論新的製圖方式，是否適用於火成岩與沉積岩混合區，並且探知海岸山脈中段地質構造型態。海岸山脈主要出露岩層為中新世火成岩層：都鑾山層，以及上新世到更新世早期沉積岩層：蕃薯寮層與八里灣層。研究製圖流程分為四大步驟：首先，將數值高程模型套入ArcGIS Pro，計算日照陰影圖與坡度圖。接著，在三維工作環境下，以不同尺度與方向的觀察視角，判釋岩層線、地層邊界與構造線。然後，計算層面與斷層面位態，並到野外查核。最後，將資料整合成更高解析度的地質圖。透過以上步驟，本研究重新繪製一張1:50000海岸山脈地區玉里地質圖，以及三條地質剖面。製圖結果顯示在火成岩與沉積岩層，可以藉由差異侵蝕的地形特徵，精細辨識岩層線與地層邊界，並增加位態數據。另外，從高解析度數值地形中，亦能觀察因植被覆蓋而過去未發現的構造。像是都鑾山層內的剪切帶與斷層：灣潭剪切帶與三間屋山斷層，位在海岸山脈西緣由深層重力滑坡變形所引起的麻汝蘭山–石公山正斷層系統，火成岩與沉積岩邊界的高角度逆斷層：樂合斷層與長濱斷層，以及花東山地區都鑾山層的單斜構造。本研究為無法到達的地方補足地質資料，且在火成岩與沉積岩混合地區，提供高精度與高解析度的製圖方式。這些製圖成果，可望在未來作為大比例尺地質研究與工程應用的基礎。

關鍵字

地質圖 ； 光達高解析度數值地形模型 ； 三維地質製圖 ； 火成岩與沉積岩混合區 ； 海岸山脈 ； 玉里

並列摘要

It is challenging to produce a large scale geologic map in Taiwan, because the dense vegetation and steep terrain in mountainous areas cause the data that can be obtained in the field is limited. Recently, airborne LiDAR-derived DEM has filtered out the vegetation covering the ground surface and exhibited bare terrain, so it has been widely used in the fault identification, landslide characterization, and geologic mapping. Previous studies have proved that high-resolution DEM has potential to improve geologic maps in sedimentary terrain and low-grade metamorphism area by interpreting geomorphic features of beddings and fault traces. This study takes the Yuli geologic map in the Coastal Range, eastern Taiwan, for example to further discuss whether the new mapping method is suitable for the igneous and sedimentary rock terrain, and to investigate structures in the middle section of the Coastal Range. The stratigraphic units in the study area mainly include Miocene igneous rock: Tuluanshan Formation, and Pliocene to early Pleistocene sedimentary rock: Fanshuliao Formation and Paliwan Formation. The mapping process is divided into four steps. First, input DEM into ArcGIS Pro, and derive hillshade and slope layer. Second, observe the terrain with different view direction and scale, and identify beddings, boundaries and fault traces. Third, calculate attitude of bedding and fault plane. Last, integrate the data and redraw the geologic map in the study area. Through steps above, this study successfully produced a 1:50000 Yuli geologic map in the Coastal Range and three geologic profiles. The results showed that in both igneous rock and sedimentary rock, by tracing differential erosion terrain, bedding traces and boundaries could be thoroughly identified, and more strike and dip data could be obtained. Besides, some new structures were explored in DEM. For example, the shear zone and the fault in Tuluanshan Formation: Wantan Shear Zone and Sanjianwushan Fault, the deep-seated gravitational slope deformation along the western edge of the Coastal Range: Majulanshan-Shihkungshan Normal Fault System, high angle reverse faults between igneous and sedimentary formation: Loho Fault and Changbin Fault, and the monocline in Tuluanshan Formation along Huatung Mountain. By using high resolution DEM, the limitation of traditional geologic mapping is concurred; moreover, the geologic information in the map is complement in igneous and sedimentary terrain. It is anticipated that the mapping result in this research will be capable to act as renovated application for geology studies and engineering purposes.

並列關鍵字

geologic map ； LiDAR-derived high resolution digital elevation model (DEM) ； geomorphic mapping in 3D environments ； igneous rock and sedimentary rock terrain ； Coastal Range ； Yuli

參考文獻

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