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首页> 外文期刊>Journal of Palaeogeography >Modern Black Sea oceanography applied to the end-Permian extinction event
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Modern Black Sea oceanography applied to the end-Permian extinction event

机译：现代黑海海洋学应用于二叠纪末期的灭绝事件

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Abstract The modern Black Sea has a mixed upper layer in the top 150–200 m of the water column, below which the water is anoxic, separated from the mixed layer by a redox boundary. There is limited vertical movement of water. Pyrite framboids form in the water column of the anoxic zone, then have been traditionally interpreted to sink immediately and accumulate in the sediments of the Black Sea. Thus the occurrence of framboids in sediments in the rock record is widely interpreted to indicate poorly oxygenated to anoxic conditions in ancient environments. However, in the Permian–Triassic boundary (PTB) microbialites of South China, which formed in shallow marine conditions in contact with the atmosphere, the published occurrence of framboids is inconsistent with abundant gastropod and ostracod shells in the microbialite. Furthermore, in the modern Black Sea, (a) framboids may be suspended, attached to organic matter in the water column, thus not settle to the sea floor immediately after formation; and (b) the redox zone is an unstable complex area subject to rapid vertical water movement including occasional upwelling. The model presented here supposes that upwelling through the redox zone can lead to upward transport of suspended pyrite framboids into the mixed layer. Advective circulation could then draw suspended framboids onto the shelf to be deposited in oxygenated sediments. In the Permian–Triassic transition, if framboids were up-welled from below the redox boundary and mixed with oxygenated waters, sediment deposited in these conditions could provide a mixed signal for potentially misleading interpretations of low oxygen conditions. However, stratigraphic sampling resolution of post-extinction microbialites is currently insufficient to demonstrate possible separation of framboid-bearing layers from those where framboids are absent. Profound differences between microbialite constructors and sequences between the western and eastern Tethys demonstrate barriers to migration of microbial organisms. However, framboid occurrences in both areas indicate upwelling and emphasize vertical movement of water from the lower to upper ocean, yet the mixed layer advective motion may not have been as effective as in modern oceans. In the modern Black Sea, such advection is highly effective in water mixing, and provides an interesting contrast with the {PTB} times.
机译：摘要现代黑海在水柱顶部150–200 m处有一个混合上层，在该层以下是缺氧水，通过氧化还原边界与混合层隔开。水的垂直运动受到限制。硫铁矿黄铁矿在缺氧区的水柱中形成，然后传统上被解释为立即下沉并积聚在黑海的沉积物中。因此，岩石记录中沉积物中黄烷的出现被广泛地解释为表明在远古环境中氧被充斥到缺氧条件。然而，在华南的二叠纪-三叠纪界线（PTB）中，在与海洋接触的浅海条件下形成的微辉石，已公布的黄酮的出现与微辉石中丰富的腹足纲和成虫纲壳层不一致。此外，在现代的黑海中，（a）浮游生物可能会悬浮并附着在水柱中的有机物上，因此在形成后不会立即沉降到海底; （b）氧化还原带是一个不稳定的复杂区域，受垂直垂直水运动的影响，包括偶尔的上升流。这里提出的模型假设通过氧化还原带的上升流可以导致悬浮的黄铁矿磁石向上迁移到混合层中。然后，顺向循环可以将悬浮的果肉吸引到架子上，以沉积在含氧的沉积物中。在二叠纪-三叠纪过渡时期，如果从氧化还原边界之下向上升起黄烷并与含氧水混合，则在这些条件下沉积的沉积物可能会为低氧条件的潜在误导性解释提供混合信号。但是，消灭后微辉石的地层取样分辨率目前不足以证明可能将含黄烷的层与不含黄烷的层分离。微恶岩构造者之间的深远差异以及特提斯西部和东部之间的序列之间的差异表明了微生物迁移的障碍。然而，在这两个区域发生的黄褐色表明向上流动，并强调了水从低层海洋到高层海洋的垂直运动，但是混合层对流运动可能不如现代海洋那么有效。在现代黑海中，这种对流在水混合中非常有效，并且与{PTB}时代形成了有趣的对比。

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