台灣西部麓山帶包括三個中新世含煤地層，由下而上分別為木山層、石底層和南莊層。前人研究多集中在中新世中後期，本研究將重心延伸到深層的木山層。這項研究收集來自苗栗地區野外露頭樣本，分析方法為岩石薄片之沉積岩岩象與X光粉末繞射分析(XRD)，並使用前人文獻中井下岩屑之生油岩評估數據，包含熱裂分析(Rock-Eval)，總有機碳分析（TOC%）與鏡煤素反射率(Ro%)。岩石薄片分析與XRD全岩分析結果顯示苗栗地區木山層礦物組成主要為石英(81.8-90.9%)，含有部份岩屑(2.7-5.1%)而長石含量少(1.4-1.8%)，礦物組成顯示沉積材料來源區地體構造為大陸區塊來源。綜合岩石薄片礦物組成對應古氣候條件，XRD黏土礦物分析之礦物組成百分比與伊萊石風化指數結果，指示出沉積環境為遠濱帶，濕潤的氣候條件，風化作用為受物理風化作用為主。生油岩評估數據顯示大部分的錦水和出磺坑井下岩屑樣本屬於低生油潛能，沉積物為IV型油母質，大多數樣品成熟度過高以致油氣散逸。;Western Foothill Belt of Taiwan includes three Miocene coal-bearing formations: namely Mushan, Shihti and Nanchuang Formations from bottom up. Based on previous middle-late Miocene studies, this study will focus on early Miocene Mushan Formation. Samples from field outcrops and boreholes were collected in this study. Analyses include petrographic thin section, XRD (X-ray diffraction analysis), Rock-Eval Pyrolysis, total organic carbon (TOC%), and vitrinite reflectance (Ro%). The results of petrographic thin section and XRD analyses indicate that mineral composition in Mushan formation, Miaoli area is mostly quartz (81.8-90.9%), some lithic fragments (2.7-5.1%) and feldspar (1.4-1.8%). Provenance terranes is indicated as continent block. Depositional sequence indicates an offshore environment. Esquevin index indicate samples exhibit physical weathering, whereas Kubler index indicate samples in deep diagenesis zone. Most of the Chinshui and Chuhuangkeng borehole samples were poor source rocks with type IV kerogen, most of samples are overmatured with already released hydrocarbon.
