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首页> 外文期刊>Brazilian Journal of Geology >Geochemical paleoredox indicators in organic-rich shales of the Irati Formation, Permian of the Paran?? Basin, southern Brazil
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Geochemical paleoredox indicators in organic-rich shales of the Irati Formation, Permian of the Paran?? Basin, southern Brazil

机译：波兰二叠纪伊拉提组富含有机质页岩的地球化学古氧化还原指示物？巴西南部盆地

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摘要

Paleoredox indicators were used to assess the depositional environment of the Permian Irati Formation, and discuss the controls on the accumulation of organic-rich sediments. Geochemical data were measured for 43 drill-core samples in southern Paran?? Basin. We infer that redox boundary was located at the sediment-water interface during the accumulation of these sediments. Trace-element data demonstrate that Irati shales were similar to average shales, except during deposition of two organic-rich beds in which U and Mo are enriched, suggesting fully anoxic conditions. The variable degree of oxygenation of bottom waters is also attested by DOP T , Fe T /Al, and sedimentological indicators of episodic ventilation. DOP T and Fe and S correlation points to an iron-limited environment, where the main sulfur sink is organic matter rather than pyrite. Cu and Cu/Mo ratio suggests bottom-water anoxia driven by increased organic flux. The Irati Formation was probably deposited in a salinity-stratified body of water, with positive water balance. The main control on the accumulation of the organic-rich sediments was the high organic carbon flux resultant from high primary productivity in surface waters. Anoxia arose as a consequence of increased productivity, not as the primary driver in the formation of these organic-rich rocks.
机译：古氧化还原指标被用来评估二叠纪Irati组的沉积环境，并讨论了对富含有机物沉积物的控制。在巴拉那州南部测量了43个钻芯样品的地球化学数据。盆地。我们推断这些沉积物的积累过程中氧化还原边界位于沉积物-水界面。痕量元素数据表明，Irati页岩与普通页岩相似，不同之处在于沉积了富含U和Mo的两个富含有机物的床，表明存在完全缺氧的条件。 DOP T，Fe T / Al和间歇通风的沉积学指标也证明了底部水的可变氧化程度。 DOP T和Fe和S的相关性指向铁限制的环境，其中主要的硫沉是有机物而不是黄铁矿。铜和铜/钼比表明由有机通量增加驱动的底水缺氧。 Irati组可能沉积在盐度分层的水体中，水平衡为正。富含有机物沉积物的主要控制措施是地表水初级生产力高而产生的高有机碳通量。缺氧是生产力提高的结果，而不是这些富含有机物岩石形成的主要驱动力。

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