由堆積中心的變遷檢視臺北盆地的構造活動

本文利用臺北盆地已有詳盡岩柱記錄的深井，劃分界定地層系統和地層厚度，並由地層堆積中心的變遷來檢視盆地的斷層構造活動。盆地的基盤面、板橋層頂界的紋泥、景美層頂界、全新世中期的海侵紀錄和現今的地表，是臺北盆地堆積史上的等時面，雖然目前仍沒有是夠的絕對年代可供參考，因此無法瞭解不同地層堆積時期盆地的構造沉陷速率，但其等時面的意義應可確立。板橋層和五股層堆積時盆地的堆積中心在西側，顯示此二地層堆積時盆地西側山腳斷層的活動頻繁;而景美層堆積時盆地有二個堆積中心，顯示景美層堆積時盆地的構造活動不僅只有山腳斷層，穿越盆地中央的崁腳斷層的沉陷量甚至可能大於西側的山腳斷層;松山層堆積時盆地的堆積中心則轉移到盆地西北角。由臺北盆地的構造作用和地形發育來看，盆地的最低處應在盆地西北側，但板橋層和五股層堆積時的盆地中心卻在盆地的西側，推測此現象可能和當時大屯火山群的火成活動使盆地北側的地表抬昇有關。

Keywords

第四紀；沉積；地層；堆積中心；臺北盆地

Parallel abstracts

In order to investigate how deposits in the Taipei Basin responded to changes in structural activity beneath Taipei, the writer examines borehole stratigraphic data of the Taipei Basin and finds that migration of deposit centers is controlled by normal faults activity surrounding the basin. It is now apparent that the basement plane of the basin, the tops of laminated mud of the Banchiao Formation, the top of the Jingmei Formation, the transgression on the Middle Holocene of the Sungshan Formation, and the recent basin surface are different isochronal planes of the Taipei Basin deposit history; however, we cannot examine the rate of sinking due to a lack of radiochronological data for the different formations deposited. The deposit centers of the Banchiao and Wugu Formations are on the western part of the Taipei Basin, indicating Shanchiao normal fault activity occurred when those two formations were deposited. There are two deposit centers evident for the period when the Jingmei Formation was deposited indicating that the sinking activities of the Kanchiao fault at the center area of the basin might be more significant than activity attributable to the Shanchiao fault. During the deposit of Sungshan Formation, the deposit center migrated to the northwestern comer of the basin. Based on structure and topographic evolution, the lowest surface of the basin should be in the northwest area; however, the lowest area is actually located in the western part of the basin formed when the Banchiao and Wugu Formations were deposited indicating that the surface of the basin might have experienced uplift due to Tatun volcanic activities when these two Formations were deposited.