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臺灣白堊紀－新生代盆地之地體演化
Tectonic Evolution of the Cretaceous- Cenozoic Basins of Taiwan
摘要
臺灣西部盆地之沉積發育及地體演化概略可分爲四個主要階段：第一階段爲從白堊紀早期的穩定大陸棚沉積到白堊紀晚期，古新世初期發生的地殼隆昇作用，造成中生界與新生界間地層之缺失，此一不整合分布廣泛。第二階段爲半地塹期，包括古新世大陸棚斷裂及沉降運動，形成臺灣北部海域各盆地及臺西，南日島盆地等，這些盆地形貌一直維持到始新世，並加上始新世又形成之澎湖盆地、雪山盆地;古新世、始新世之古海岸線主要受大陸棚斷裂方向之影響，當時澎湖以南之海域及北港以南之臺灣島，皆爲陸地。漸新世早期，現今臺灣中央山脈軸心以西皆隆起成爲侵蝕帶，這現象並配合中期以後漸新世全球大海退，因此造成臺灣第三紀中面積廣大的不整合面。臺灣古新世及始新世之盆地架構，在這次大海退後就消失，以後的沉積不太受前期大陸棚斷裂構造因素控制，代之而起的是第三階段之被動大陸邊緣期。由於北港及觀音二高區的形成，一直影響著晚期漸新世，中新世及上新世早期之沉積;第三階段整個大陸邊緣呈現較快速的沉降，北部大致以新竹，苗栗一帶爲沉積中心，沉積物來源以西邊或西北邊爲主，南部則增加了新形成的澎湖，北港以南之南部盆地；第四階段爲弧陸碰撞期，其盆地之地層與沉積之演變，於上新世晚期更新世時期，由於受菲律賓板塊的碰撞，臺灣造山運動急劇進行，此時臺灣已逐漸形成臺灣海峽並持續的沉降，第四階段之沉積最厚地區已由新竹，苗栗一帶，逐漸轉變爲臺中南投一帶，沉積物來源亦改成以東邊爲主。
並列摘要
The depositional history and tectonic evolution of the Western Taiwan Basins can be documented in four stages. The first stage: This stage represents the period between Early Cretaceous,which was dominated by stable continental shelf deposits, and Late Cretaceous-Early Paleocene, which was characterized with crustal uplifts. These uplifts had resulted in the erosion of strata and consequently the formation of the wide-spread Mesozoic-Tertiary unconformity. The second stage: Half-graben stage. The rifting and subsidence of the continental margin in Paleocene had resulted in the formation of various basins in the offshore northern Taiwan as well as the Taihsi and Nanjihtao Basins. The configuration of these basins remained unchanged in Eocene when the Penghu and Hsueshan Basins started to develop. The paleo-coastline in Paleocene and Eocene was controlled by the rifting pattern of the continental shelf and landmass existed south of Penghu and Peikang. The areas west of the present Central Range axis was all uplifted and being eroded in early Oligocene. This uplift phenomenon and the Oligocene global sea level regression were concurrent and thus resulted in the vast unconformity in theTertiary of Taiwan. The Paleocene and Eocene basin configuration disappeared after this sea level regression and the consequent sediment deposition was no longer controlled by the previous structural lineations initiated by continental rifting. The third stage: Passive continental margin stage. The Peikang and Kuanyin Highs had significant impact on the sedimentation in Western Taiwan Basins during Late Oligocene, Miocene. and Early Pliocene. The whole continental margin was marked by relatively rapid subsidence in this stage and the depositional centre in northern Taiwan was located in Hsinchu-Miaoli which was mainly sourced from the west and northwest. The Southern Basin south of Penghu and Peikang is initiated during this stage in southern Taiwan. The fourth stage: Arc Continent collision stage. The stratigraphy and sedimentation of the Western Taiwan Basins were affected by the rapid orogeny resulted from the collision of446m the North Luzon Arc in late Pliocene Pleistocene. The present Taiwan Strait was formed and had been in rapid subsidence since then. The depocentre with thickest sediment shifted from Hsinchu-Miaoli to Taichung-Nanto in this stage and the source of sediments was mainly from the east.