應用空載光達數值地形解析海岸山脈南段地質構造

Abstract

海岸山脈是菲律賓海板塊與歐亞板塊弧陸碰撞作用下的產物，記錄了島弧火山從出生到死亡的歷史。其主要由火成岩及沉積岩組成，火成岩區地勢高聳、植被分佈茂密且野外觀察不易，前人的野外位態資料相較沉積岩區來得稀缺，進而對地質構造抱持不同見解。由此可見，海岸山脈火成岩區地質構造尚待後人釐清。此外，新一代地質圖製圖帶有不確定性，如何說明製圖的不確定性亦為本文欲解決的問題。本文研究區域為玉里地質圖幅以南的海岸山脈地質區，旨在利用空載光達產製的2米解析度數值地形解析研究區域內地質架構及歷史：將數值地形輸入ArcGIS Pro後，於三維環境藉由視角轉換繪製數值地形之構造線型，同時將地形根據層理地形特徵強弱分為四類。接著計算迴歸平面位態、實際至野外以UAV輔助查核，並輔以前人文獻，釐清研究範圍內地質架構的同時，補足都鑾山層位態資料。最終產製新一代海岸山脈南段五萬分之一地質圖及層理地形分級圖。繪製成果顯示，運用高解析度的數值地形進行三維判釋有助使火成岩與沉積岩的地層邊界更加精確。找出都鑾山層中斷層構造（如：成廣澳斷層、七里斷層、小馬斷層以及石厝溝斷層）的同時，使花東山斷層分佈的位置更加明確。並發現前人未曾報導過的羅山剪切帶、萬人山正斷層系統以及泰源盆地南端的大規模山崩。本研究以三維地形製圖解析海岸山脈南段地質構造，精進五萬分之一地質圖，提高製圖解析度；並將層理地形特徵根據強弱進行分級，初步說明了地形製圖的不確定性；而UAV輔助查核則獲取地勢高聳及遙遠處露頭資訊，使海岸山脈南段野外露頭資訊更為完整。研究成果將可作為未來地質研究及工程施作參考。

The Coastal Range of Taiwan is a product of the arc continent collision between the Philippine Sea Plate and the Eurasian Plate, which records the history of island arc volcanoes from birth to death. Coastal Range is mainly composed of igneous rocks and sedimentary rocks. The igneous rock area has a high terrain, dense vegetation distribution, and field observation is not easy. Compared with the sedimentary rock area, field data within the igneous rock area is scarce, which lead to different views on the geologic structure. Geologic structures of igneous rock area in the Coastal Range have yet to be clarified. In addition, there are uncertainties of the new generation geological mapping, how the uncertainties to be explained is also a problem to be solved by this study. The research area of this study is the southern part of Coastal Range. This study aims to use the 2-meter resolution airborne LiDAR derived DEM to study the geologic structure and the history of the area. After inputting the DEM into ArcGIS Pro, this study delineated the structure lineament in the 3D environment through different perspectives, at the same time, ranking the terrain into four types according to the strength of the bedding topographic features. Calculaing the attitude data of the bedding regression plane then go to field to verify the delineated results. Supplemented by previous study, this study clarifies the geological structure within the research area, and to supplement the attitude data in the Tuluanshan Formation. Finally, a new generation of 1/50,000 geological map and bedding characteristic ranking map of the southern Coastal Range were produced. The mapping results show that using high-resolution DEM for 3D interpretation makes the stratigraphic boundaries between igneous and sedimentary rocks more precise. While finding out the fault structure in the Tuluanshan Formation (such as: Chengguang'ao fault, Qili fault, Xiaoma fault and Shicuogou fault), the location of the Huatungshan Fault distribution become clear. This study also discovered the Loshan shear zone, the Mt. Wanren normal fault system, and the large-scale landslide at the southern part of the Taiyuan Basin, which have not been reported before. In this study, 3D topographic mapping is used to analyze the geologic structure of the southern Coastal Range, and the 1/50,000 geologic map is refined to improve the mapping resolution, and the bedding topographic characteristics are ranked according to their strength, which preliminarily explains the uncertainty of topographic mapping. The UAV-assisted verification obtains information on high-lying terrain and outcrops in distant places, making the information on outcrops of the southern Coastal Range more complete. The research results can be used as a reference for future geologic research and civil engineering.