首页> 外文期刊>Sedimentology: Journal of the International Association of Sedimentologists >Mudstones of the Tanqua Basin, South Africa: an analysis of lateral and stratigraphic variations within mudstones, and a comparison of mudstones within and between turbidite fans
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Mudstones of the Tanqua Basin, South Africa: an analysis of lateral and stratigraphic variations within mudstones, and a comparison of mudstones within and between turbidite fans

机译:南非坦夸盆地的泥岩:对泥岩内横向和地层变化的分析,以及浊浊扇内和之间的泥岩比较

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摘要

Permian deep-water mudstones in the Tanqua Basin, South Africa, have been studied using geochemical and spectral gamma ray techniques. The mudstones occur as thick sequences between sand-rich submarine fans, but also occur as thinner mud-rich units within each fan. The interfan mudstones are interpreted to have accumulated during transgression and the consequent period of relatively high sea-level, while the submarine fans and their intrafan mudstones were deposited during regression and relatively low sea-level. Geochemical analyses revealed systematic differences between interfan and intrafan mudstones because the two types of mudstones have slightly different source lithologies. Differences between the two types of mudstone suggest that changes in relative sea-level played a role in controlling exposure of sediment source areas. There are geochemical signals that display systematic stratigraphic trends within both interfan and intrafan mudstones. These are best explained by gradual denudation, exposure and weathering of different lithologies within a single sediment source area. Both interfan and intrafan mudstones have uniform geochemical signals along the flow direction except for the relative amount of uranium. It is most likely that the basinward increase in uranium in the mudstones is the result of reduced clastic dilution of uranium-bearing pelagic fallout.
机译:南非坦夸盆地的二叠纪深水泥岩已使用地球化学和光谱伽玛射线技术进行了研究。泥岩在富砂海底风机之间以较厚的序列出现,但在每个风机内也以较薄的富泥单元出现。扇间泥岩被解释为在海侵期间和海平面相对较高的时期积累,而海底扇及其扇内泥岩则在回归和海平面相对较低的时期沉积。地球化学分析显示,扇间和扇内泥岩之间存在系统差异,因为两种类型的泥岩的源岩性略有不同。两种类型的泥岩之间的差异表明,相对海平面的变化在控制沉积物来源地区的暴露中发挥了作用。有地球化学信号显示扇间和扇内泥岩内部的系统地层趋势。最好通过在单个沉积物源区内逐渐剥蚀,暴露和风化不同岩性来解释这些现象。除铀的相对含量外,扇间和扇内泥岩沿流动方向均具有统一的地球化学信号。泥岩中铀向盆地的增加很可能是含铀中上层沉积物碎屑稀释减少的结果。

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