臺灣西南部古亭坑層有孔蟲化石的氧同位素地層

臺灣西南部麓山帶的泥岩出露面積相當廣，但由於其岩性單調、眉理不明顯，常使地層界限的追蹤和對比發生困難，因此本文嘗試藉由泥岩地層中浮游性有孔蟲化石的氧同位素地層，來建立泥岩地層更詳細的地質年代參考座標。研究結果顯示，利用泥岩地層中保存良好的海相化石的氧同位素地層，來建立臺灣西南部泥岩年代地層的劃分和對比是值得考慮的可行方法之一。雖然受到造山運動的推升而出露在陸上的海相地層中的海洋微體化石，其殼體的碳氧同位素組成很容易受到二次結晶作用的影響，但由海相化石碳氧同位素組成明顯的往負(輕)的方向偏移，可以判別出出露在地表的海相地層中的有孔蟲化石受到再結晶作用的影響。本研究利用上新世/更新世的界限附近，末受到再結晶作用所影響的有孔蟲化石的氧同位素組成，透過與深海岩芯的對此顯示其相當於氧同位素地層63至73階，年代約為1.755至1.955Ma 之間，其中氧同位素地層第66階是臨近各冰期中最重(正)的，可能是受環境因素的影響所致，值得進一步討論。

關鍵字

浮游性有孔蟲；氧同位素地層；地球化學；古亭坑層；臺灣西南部

並列摘要

A large area in the foothills of southwestern Taiwan is composed mainly of a very thick marine mudstone sequence that is intercalated with thin-bedded sandy layers. Not is it difficult to identify the bedding plane or boundary in the mudstone sequence, but also it is very difficult to establish correlations with different formations. In this study, planktonic foraminifera isotope stages were used to construct a detailed age model for stratigraphic correlation in the Lower Gutingkeng Formation for the first time. For microfossils in ancient marine sediments, a likely factor that may overprint the pristine original geochemistry record is post-depositional diagenesis However, a previous study showed both carbon and oxygen isotopic compositions shifting: toward a more negative value for the evaluation of diagenetic artifacts of deeply buried sediments that have been uplift on land. The Pliocene/Pleistocene boundary for shells of foraminifera in the study area is free of carbonate recrystallization. Correlation between oxygen isotope stratigraphy in this study and deep-sea sediments shows that the oxygen isotope stage s arc from 63 to 73 and that the age is from 1.755 to 1.955Mn. In this study, the oxygen isotope composition of stage 66 is marc positive than that of nearby stages, which is in need of further investigations.

並列關鍵字

Planktonic foraminifera ； oxygen isotope stratigraphy ； geochemistry ； Gutingkeng Formation ； southwestern Taiwan

國際替代計量

臺灣西南部古亭坑層有孔蟲化石的氧同位素地層

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