台湾西部前陆盆地的构造格局和演化规律

基于对台湾岛、台湾海峡和周边海域(南海、东海)的盆山系统、相应动力学机制、构造单元以及其他诸多造山带和毗邻前陆盆地的研究,提出了台湾西部前陆盆地演化的4阶段模式,即:①增生楔发育-单向物源阶段;②挠曲响应-双向物源阶段;③前陆盆地系统形成阶段;④造山带坍塌-前陆衰退阶段。并对各阶段的构造特征、沉积特征和物源供给方式的差异给予了探讨,认为在增生楔发育-单向物源阶段,尽管增生楔业已推覆至陆缘层序之上,但盆地依然呈被动陆缘的外廓特征,以大陆方向为盆地的唯一物源;在挠曲响应-双向物源阶段,盆地开始明显出现挠曲响应,增生楔开始具备并逐步加大向盆地供应沉积物质的能力,但依然以大陆方向为主要物源方向;在前陆盆地系统形成阶段,前渊和前隆区逐步形成,在来自唯一物源、后陆方向造山带物质的快速充填下,前陆期层序快速向前隆方向超覆,形成典型的前陆楔形体;在造山带坍塌-前陆衰退阶段,伸展作用出现并快速扩展,前渊抬升,前陆层序遭受剥蚀,火山作用重新出现。并探讨了该模式是否具有周缘前陆盆地的普遍适用性。

STATIC FRAMEWORK AND DYNAMIC EVOLUTION OF WESTERN TAIWAN FORELAND BASIN

Based on research about the trench-arc-basin system, its geodynamic mechanism, tectonic units like orogens and forelands, a 4-stage model about the evolution of Western Taiwan Foreland Basin was proposed in this paper. The model consists four stages, namely, 1. Stage of accretionary wedge development - unidirection source. Although the developing accretionary wedge was superimposed on the passive continent strata (PCS) during this phase, the profile of basin still retains characteristics of classical PCS and the continent remains as the only source of material for depositing. 2. Stage of response of flexing - bidirection source. During this phase response of flexing is becoming more and more evident, accretionary wedge begins to play an increasingly important role of supplying material to basin, but the continent is still the major source of material for deposition in the basin. 3. Stage of formation of foreland system. During this phase foredeep, especially forebulge, was formed. The spectacular orogen in the hinterland becomes the major source of depositing materials. The classical foreland depositional wedge is formed and overlaps towards the forebulge gradually. 4. Stage of collapsing of orogen - waning of foreland. During this phase extension commences and expands rapidly. Denudation happens to those foreland strata owing to the uplifting of foredeep and volcanism appears again impressively. Eventually, discussions were made about a detailed explanation on hard-to-be-unraveled questions available and some further thoughts were proposed.