本研究綜合台灣西北部海域及陸域之反射震測剖面與井測資料，繪製前陸盆地堆積時期各地層的時間深度構造圖、等時線圖與等深度圖；研究晚漸新世五指山層至早更新世下部頭嵙山層的沉積環境與層序地層。藉此來討論台灣西北部，漸新世至更新世盆地之演育過程與層序變化。 震測剖面之分析結果顯示，五指山層至頭嵙山層，各層頂部之深度由東向西逐漸變淺。南港層與其下伏地層，東西向之厚度變化不大，南莊層由東往西尖滅；前陸盆地時期桂竹林層至頭嵙山層以往西上覆之型態堆積於觀音高區上。 前陸盆地各地層之深度構造圖顯示，盆地形貌最深處位於研究區域南端。盆地走向自西北端的東北-西南走向，往南漸變為東北東-西南西走向與前陸盆地發育前之張裂盆地走向一致，顯示前陸盆地發育前之盆地形貌對前陸盆地發育，有重大的影響。地層等厚度圖顯示，盆地沉積中心由西北向造山帶*東南方)加深。 本研究分析6口之電測相，區分出8類沉積環境，包括2種淺海大陸棚環境、3種海岸環境與3種陸相環境； 3類主要的沉積體系: 1. 波浪為主的河口灣-堰洲島沉積體系、2. 波浪為主的潟湖沉積體系、3.波浪和暴風為主的淺海大陸棚沉積體系。再由沉積環境的垂直變化，建立9種次層序，以次層序疊加方式，於五指山層至中段桂竹林層間，解析20個層序。 被動大陸邊緣時期沉積環境受控於全球海水位面變化，呈現數個大陸棚-海岸環境的循環；前陸盆地則受造山發育與遷移的影響，沉積環境由桂竹林層之遠濱-濱面相環境，向上加深為遠濱相或遠濱-濱面相環境的錦水頁岩，而後向上變淺為頭嵙山層的陸相環境。 The tectonic environment in NW Taiwan and its vicinity is a latest Miocene ~ Recent foreland basin developing on top of mid-Oligocene to Miocene passive-margin sequences. This study integrated reflection seismic and well-log data to reveal the stratigraphic development in the study area since the Oligocene by combined analysis on well-log sequences and mapping of sediment thickness. Seismic data show that all the stratigraphic units deepen toward the east due to orogenic loading. Stratigraphic units deposited during Oligocene to Miocene passive-margin stage show no distinct thickness variation in the east-west direction with the exception of the Nanchuang Formation. This formation abruptly terminates against the offshore Kuanyin basement high in the west, interpreted as extensional fault-controlled deposition. Stratigraphic units of the foreland basin thicken toward the Taiwan orogen and thin westward toward the Kuanyin basement high. Seismic mapping show that the depositional strike of the foreland basin changes from NE-direction in the west to NEE-direction in the east and southeast. This indicates that the pre-existing NEE-striking extensional basin center during the deposition of the Nanchuang Formation has facilitated later foreland subsidence. Analysis on wireline log facies identifies 8 types of paleo-environments ranging from offshore to fluvial environments. The vertical change of paleo-environments indicates that there are 9 types of parasequences in the Oligocene-Pleistocene succession. This study recognizes 20 sequences through the study of stacking patterns for individual parasequence and identifications for major stratal surfaces. Our results indicate that the passive-margin succession consists of a few offshore-coastal sedimentary cycles and those cycles roughly correspond to eustatic sea-level changes. By contrast, the foreland basin succession is floored by a deepening-upward succession (i.e. from Kueichulin Formation to Chinshui Shale) followed by an overall shallowing-upward trend (i.e. from Cholan Formation to Toukoshan Formation). The later shallowing-upward trend is apparently controlled by the growth and encroachment of Taiwan orogenic belt east of the study area.
