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Lithofacies and Biofacies Analyses and Reconstruction of the Pli-Pleistocene Evolution of the Orogenic Belt and Foreland Basin in Central Taiwan
|Contributors: ||NTOU:Institute of Applied Geosciences|
|Issue Date: ||2011-06-28T07:13:36Z
|Abstract: ||摘要:為了了解台中地區頭嵙山層的沉積環境變化以及台中前陸盆地的演變過程，本研究選擇了麓山帶、大肚台地、清水海岸平原的野外露頭及井下岩心的資料，來從事岩性觀察和岩相分析，並使用生物地層的資料輔助時間上的先後順序，探討在更新世頭嵙山層的沉積環境演變過程。 在沉積岩相分析方面，一共區分出9 種岩相，並歸納成6種岩相組合，並分別解釋為陸上的礫岩辮狀河、砂質辮狀河和曲流河等環境，海陸交界的潮坪環境，以及海域的濱面和遠濱的環境。 在麓山帶、大肚台地及清水海岸平原的環境演變過程，是從一開始的海相的遠濱環境開始，逐漸陸化變成陸相的辮狀河環境。麓山帶首先抬昇，台中盆地為其前陸盆地，後來大肚與后里台地繼續抬昇，使得麓山帶併入前陸盆地褶皺衝斷帶，台中盆地亦轉為背負型盆地，清水海岸平原則是成為新的前陸盆地沉降而累積沉積物。清水海岸平原因為前陸盆地的沉降而造成二次的海水入侵，其時間分別在46 萬年前到26 萬年前(NN20 超微化石帶)以及26 萬年前至今日(NN21 超微化石帶)。整個區域的環境變化顯示前陸盆地的演變是持續由東向西往歐亞大陸板塊的方向移轉，而舊的前陸盆地則依續併入造山帶中。|
abstract:In central Taiwan, the outcrops and cores of the western Foothill, the Dadu Tableland and the Chingshuei Coastal Plain were studied for lithofacies analysis. The lithofacies and biofacies data are then integrated to interpret the paleo-environments from the late Pliocene to Pleistocene time. Nine lithofacies are recognized and ascribed into six facies associations. The six facies associations are interpreted respectively as conglomerate braided river, sandy braided river, meandering river, tidal flat, shore face and offshore environments. Based on the temporal and spatial distributions of the six facies associations the evolution of the regional environments and it accompanied tectonic processes have been discussed and reconstructed. In general, from the Pliocene to Pleistocene time, the paleoenvironment of the central Taiwan is evolved from an offshore shallow-upward into a terrestrial braided river setting. From east to west, along the course of orogeny, the eastern studied area was first uplifted from foreland shallow marine into coastal environment. Meanwhile, the present Taichung Basin was subsided into shallow foreland basin.Through the Pleistocene, the Dadu and Houli tablelands were thrusted and arised. In the same time, the Pliocene eastern coastal environment was uplifted further merging into foreland foldthrust belt as the present western Foothill, the western-most part of the Taiwan Orogeny. Behind the thrusted tableland, the area was relatively subsided resulting in the Taichung piggyback basin. Westward, in front of the tableland, the newly formed foreland basin was infilled into the Chingshuei Coastal Plain. According to the evolution of the regional environments, the Taiwan orogeny was continually evolving westwards. As a result, the foreland basin gradually switched its location from east to west. The previously existed foreland basin was sequentially thrusted and merged into the Orogenic belt.
|Appears in Collections:||[應用地球科學研究所] 研究計畫|
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