| 摘要: | 台灣造山帶將侵蝕沉積物搬運到沉積盆地中，除了岩石碎屑沉積物以外，同時有機材料也會經來源區侵蝕後隨著沉積系統搬運到沉積盆地。隨著沉積物加積埋藏，有機物在經過埋藏受到生物降解以及熱埋藏的影響開始分解以及碳化，這些有機材料將會記錄盆地埋藏的歷史。另一種觀察盆地埋藏的方法則是黏土礦物轉化，也是觀察盆地埋藏重要的證據。台灣西部前陸盆地有機成熟度過去已有大量研究，本研究選擇台灣東部海岸山脈弧前盆地做為研究區域。六條剖面由北而南分別是水璉北溪、豐濱、奇美、樂合溪、三仙溪以及馬達吉達溪採集砂泥岩樣本後浮選有機質，進行鏡煤素反射率量測以及熱裂分析。除此之外，本研究以X-光繞射以及短波紅外光法，觀察盆地埋藏訊號。六條海岸山脈剖面鏡煤素反射率均反映浮選的有機材料有往年輕地層鏡煤素反射率變高的趨勢，且標準差大，所量測的反射率分布較為離散﹔然而碳化漂木的鏡煤素反射率則隨著埋藏深度而增高。搭配熱裂分析結果，較有顯著差異的是南段馬達吉達溪剖面的蕃薯寮層有幾個樣本S1高於S2峰，而幾乎所有八里灣層的S2峰特高。另一個特點是三仙溪剖面有些樣本Tmax均小於400 ̊ C。利用海岸山脈八里灣層和蕃薯寮層採集的樣本進行鏡煤素反射率量測以及熱裂分析，顯示樂合溪以及馬達吉達溪的蕃薯寮層已經進入初期成熟階段，透過反射光觀察主要材料來源為III型（鏡煤素）、IV型（惰煤素）為主產氣型材料。而浮選有機材料之年輕地層鏡煤素反射率變高，反映了再積性有機材料之影響。在黏土礦物方面，水璉北溪剖面（均採自蕃薯寮層）與馬達吉達溪剖面則的短波紅外光譜（SWIR）均觀察到反射光譜在1900nm黏土礦物層間水特徵吸收峰（D1900）吸收深度逐漸減小。然而在馬達吉達剖面中SWIR轉化的機制也反映了在深度2000m以下的層間水特徵吸收峰吸收深度（D1900）逐漸減小，暗示了地層隨著埋藏而黏土礦物層間水減少。本研究也利用拉曼光譜碳質物方法分別根據脊梁山脈東側六條河川滾石和海岸山脈三條剖面之水璉礫岩進行分析，經觀察可發現脊梁山脈東側六條河川滾石溫度隨著往南變低。海岸山脈礫岩層中採集的礫石可發現北段水璉礫岩較馬達吉達溪剖面在2Ma時期所接收的礫石變質溫度較高。而沉積年代在1.24-1.07 Ma的奇美剖面礫岩層已經接收到較高變質程度的礫石。另一方面，再積性鏡煤素反射率在2-3.99%的再積材料在六條剖面的蕃薯寮或八里灣層均有，且可比對到葡萄石-綠纖石相，此現象可指示海岸山脈沉積年代3.35Ma板岩層已經出露到地表接受侵蝕且沉積到海岸山脈。鏡煤素反射率1-1.99 %於北邊四條剖面擁有較高比例，說明了北邊四段剖面持續且大量接收此反射率來源區的材料。;Taiwan orogeny eroded sediments then transported to adjacent basins. The eroded materials contain not only detrital from inorganic rocks but also organic matters. After the sediments being deposited in basin, organic matters prone to bio-degradation and coalification through burial time, and preserve the basin burial history. Transformation of clay mineral is another technique to observe basin burial history. Although there are many thermal burial history studies in western Taiwan because of the evaluation petroleum potential, however Coastal Range of eastern Taiwan is comparingly less studied. So, it served as a good candidate to observe the thermal burial history. This study collected sedimentary rocks and coalified woods from north to south with Shuilien, Fengpin, Chimei, Loho, Sanshien, and Madagida sections. We used the coalified woods and separated organic matters from sedimentary rocks and made into pellets to measure their vitrinite reflectance (Ro%). Furthermore, Rock- Eval pyrolysis was applied to acquire the Tmax, a parameter for maturity evaluation. Additionally, X-ray Diffraction (XRD) and Short Wavelength Infrared (SWIR) techniques were used in this study. Ro% of Separated organic materials showed increase and highly disperse through younger upward of stratigraphic column, on the other hand, the coalified woods exhibited increase Ro with depth. Combined with Rock-Eval pyrolysis method, Madagida section showed some S1 peak higher than S2 peak, and Tmax lower than <400 ̊ C in Sanshien section. The result indicates organic matters from Fanshuliao Formation of Loho and Madagida sections belonged to early mature stage, with gas prone organic matters (Type III, IV). The upward increase of Ro% implied inclusion of the reworked detritus organic materials. On the other hand, clay mineralogy such as SWIR from Shuilien and Madagida sections, exhibited D1900nm decreased through burial depth of selected stratigraphic columns. Finally, Raman Spectrocopy Carbonaceous Materials (RSCM) was also used in this study, the results of the northern part Coastal Range had receveived relative higher metamorphic grade gravel sediments than southern part in 2Ma. However Chimei section in the central part of Coastal Range had received gravel sediments with metamorphic grade up to green schists facies. Compared with the reworked vitrinite reflectance results, Ro% constraint in 2-3.99 indicated six sections of Coastal Range received sediments with the Prehnite -Pumpellyite facies since 3.35Ma. |
