摘要
沉积历史的分析表明,华南古大陆边缘带经历了三个阶段的板块构造演化:裂谷作用阶段(?一Z)以发育北东向地堑地垒为特征.被动大陆边缘阶段(Z—O)主要是稳定下沉与沉积充填作用;陆架边缘随时间发生大规模向海推进;大陆边缘沉积特征从早期至晚期渐趋规则、统一.闭合造山阶段(O—S)前期大陆边缘急剧下沉,台地变为深水盆地;晚期接受来自与前期物源完全相反方向的大量粗碎屑物质,以至最终隆起成山.
Abstract
The analysis of sedimentary history indicates that, paleocontinental mar-gin in South China underwent multistage plate tectonic evolution of rift, pas-sive margin and clousure orogeny from Late Presinian to Silurian. A series of grabens stretching NE developed during the rift stage(Presinian-Early Sinian). they were filled with a series of coarse clastic rocksmainly by gravity flow and intercalated beds of basaltic volcanic breccia whichbelongs to A- series or T-series on the diagram of NaO+KO versus SiOand tuff. Isolated carbonate platforms and ambient deeper-water basins weredeveloped inside the young passive margin(Middle Sinian-middle Early Camb-riam), and then sedimentary filling made it an extensive shallow-water car-bonate platform: deep-water starved basins appeared rapidly after the rifting. In the outer side of the young passive margin, only silicalite of tens ofmeters thick was developed. Matured passive Margin(late Early Cambrian-Early Ordovician) was characterized by the development of a huge carbona-te wedge along the shelf break zone. In the outer shelf and shelf margin,algal reefs and carbonate banks usually developed well: the associationof slope and slope-toe was dominated by various kinds of gravity flow se-diments in the early stage and was characterized by contourites in the latestage; pelagic laminated marls and shales developed in the basin. Ano-ther important character was that the shelf margin migrated towards sea,leading to distictive prograding sedimentation on the slope. During theclousure orogeny stage of the Middle Ordovician-Silurian, the direction ofsediment transportation changed opposite, and coarse clastics prograded pro-gressively from southeast to northwest even overlapped onto the central partof the paleo-Yangzi Plate. This process formed a shallowing-upward se-quence which composed of a thick clastic rock that changed from turbidites inbottom to coastal sediments in top till continental deposits. This orogenyfinally ended up with the widespread uplift in the end of the Silurian.
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