| 摘要: | 前人於馬達吉達溪區域出露的八里灣層與蕃薯寮層之磁地層與生物地層(浮游性有孔蟲、鈣質超微化石)整合研究，測定了上新世-更新世快速沉積的地層年代，剖面年代跨距自3.4Ma以迄約1.2Ma，其中有一長時間的地層缺失，約始於2.92Ma以至2.1Ma；另於三仙溪區域之研究，測定其年代跨距自1.69Ma至0.7Ma，綜觀前人對此區域尚未有以岩樣有機物成分為主的研究。本研究結合有機物地化分析與前人無機物的研究資料，討論海岸山脈南部不同地層單位之沉積環境變遷。使用的研究方法有三，一為煤岩分析鏡煤素反射率(Ro%)；二為Rock-Eval 熱裂分析，探討有機質成熟度，得到地層岩樣碳氫化合物含量與特性；三為X-射線繞射分析(XRD)，用於檢測岩樣的礦物組成。煤岩分析顯示馬達吉達溪露頭，較深較老的蕃薯寮層之Ro為0.5至0.8%，較淺年輕的八里灣層為0.8至1.2%，Tmax一致約430℃，均屬於成熟的有機材料。三仙溪岩層露頭均屬八里灣層，資料大致分為兩個群落，Ro為0.8至1%，Tmax為430℃屬成熟有機材料；Ro為0.3%，Tmax約為370℃，屬未成熟的有機材料。由碳化漂木的偏低Ro值，可知八里灣層之成熟有機材料應為外地生，未成熟有機材料應為本地生。進一步進行樣本XRD分析，確認材料的可能來源。由馬達吉達溪之XRD全岩分析初步分析結果，可知材料之礦物包含伊萊石、石英、方解石等，但因石英訊號太強，會降低黏土礦物成分的訊號可信度，故進一步利用化學方法，去除海鹽、碳酸鹽與降低石英成分後，再經由XRD儀器分析得到黏土礦物成份，以伊萊石為指標黏土礦物。煤岩分析的結果與伊萊石成分分析結果相比較，顯示年輕地層確實有來自中央山脈的材料變質。;Past study about magnetic and biostratigraphy from planktonic foraminifera and calcareous fossils of Baliwan formation and Fanshuliao formation in the Madagida-chi area and determined the stratigraphic age is the Pliocene-Pleistocene with rapid deposition. The profile spanned from 3.4 Ma to 1.2 Ma with a long time missing hiatus starting from 2.92Ma to 2.1Ma. On the other hand, the study of Sanxian-chi area determined the age is from 1.69Ma to 0.7Ma .However, in sedimentary rocks had not been thoroughly studied. This study combines the analysis of organic matter with previous inorganic studies so as examine the depositional environment of stratum units in the southern Coastal Range of Taiwan. Rock-Eval pyrolysis is used for maturity and characteristics of organic matters. Then, X-ray Diffraction analysis (XRD) is used to detect mineral composition especially clay minerals. In Madagida-chi area, the deeper Fanshuliao Formation exhibits Ro values from 0.5 to 0.8%, whereas the shallower Baliwan Formation exhibits Ro value from 0.8 to 1.2%. Tmax of both formations have a similar value about 430 °C. On the other hand, outcrops of Sanxian-chi belong to Baliwan Formation, the data can be divided into two groups：1) Ro value 0.8 to 1%, and Tmax is 430 ℃, a matured organic material. 2) Ro 0.3% and Tmax is about 370, an immature organic materials. Additionally from Ro of carbonized wood, it can be seen that the mature organic material of Bailiwan Formation should be allochthonous origin, whereas the immature organic material should be autochthonous material. XRD analysis was further performed to confirm possible sources of the material. According to results of XRD, most of samples from Madagida-chi contain illite, quartz and calcite. Because the signal of quartz is so strong that will influence the signal of other clay minerals, chemical method was performed to remove the salt, carbonate and quartz, before analyzing clay mineral composition. Finally the results of petrographic analysis are compare with the results of XRD, it confirmed that the metamorphic material from Central Mountain Range had been included in Baliwan Formation. |
