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首页> 外文期刊>Precambrian Research >Shallow water anoxia in the Mesoproterozoic ocean: Evidence from the Bashkir Meganticlinorium, Southern Urals
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Shallow water anoxia in the Mesoproterozoic ocean: Evidence from the Bashkir Meganticlinorium, Southern Urals

机译：浅水缺氧在中环佐科奇海洋：来自Bashkir Mugicaltlium的证据，南乌拉尔斯

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The apparent lag between the first permanent rise of atmospheric oxygen to appreciable levels and oxygenation of the deep ocean has focused efforts in deciphering the evolution of seawater chemistry across the Proterozoic Eon (2.5-0.542 Ga). It is generally accepted that from similar to 1.85 Ga oxic shallow marine waters were widespread while the deep ocean remained dominantly ferruginous (Fe(ID-rich), with episodic euxinia confined to productive continental margins and intracontinental basins. The geochemical record that informs this picture, however, is currently sparse, and further studies are required to adequately evaluate temporal and spatial variability in ocean redox conditions across this vast expanse of time. Here, we report Fe-S-C systematics, alongside major (Al, Mn) and trace metal (Mo, U) data for similar to 1.6-0.8 Ga marine sediments from the Bashkir Meganticlinorium (BMA), Southern Urals, Russia. Our Fe speciation data reveal a water column dominated by ferruginous conditions, no evidence for euxinia, and oxygenated waters confined to only the shallowest, near coastal settings. Trace metal data support these findings, with Mo and U enrichment factors in anoxic sediments implying the operation of a particulate Fe (oxyhydr)oxide shuttle under ferruginous conditions as the main mechanism for generating moderate authigenic Mo enrichments. Sulfur isotope systematics imply that predominantly low dissolved sulfate concentrations prevailed throughout the deposition of the BMA succession, which, in combination with a low organic carbon loading, promoted the development of ferruginous, rather than euxinic, water column conditions. The restriction of oxic conditions to the shallowest, near-coastal depositional settings within the Bashkir basin contrasts to other redox studies from this period. Such discrepancies highlight major uncertainty in our understanding of the temporal and spatial evolution of water column redox chemistry across the Mesoproterozoic Era,
机译：第一次永久性氧气之间的明显滞后与深海的明显水平和氧合的氧气已经致力于破译海水化学的演变，在正古代EON（2.5-0.542 GA）上。普遍认为，从类似于1.85的GA良浅海水水域普遍存在，而深海仍然是占型铁素（Fe（富含Fe），局限性的exinia局限于生产的大陆边缘和脑内盆地。地球化学记录通知这幅画然而，目前是稀疏的，并且需要进一步的研究来充分评估在这个广泛的时间内的海洋氧化还原条件下的时间和空间变异。在这里，我们报告Fe-SC系统，以及主要（Al，Mn）和痕量金属（ Mo，U）类似于Bashkir Muticinallorium（BMA），南乌拉尔州的1.6-0.8 Ga海洋沉积物。我们的FE形态数据揭示了由铁艺条件下辖的水柱，没有肠炎的证据，并限制氧气水域只有最浅的，近沿海设置。跟踪金属数据支持这些调查结果，用MO和U富集因子在缺氧沉积物中暗示了术语的操作在铁素条件下吃Fe（氧水）氧化物梭是产生中度Authigenic Mo富集的主要机制。硫同位素系统暗示，在BMA连续的整个沉积中，主要是低溶解的硫酸盐浓度，其与低有机碳载荷组合，促进了铁素，而不是肠道水柱条件的发育。在Bashkir盆地内对氧化条件到最浅的，近沿海沉积设置的限制对比此时的其他氧化还原研究。这种差异突出了我们了解我们对中索古代时代水柱氧化还原化学的时间和空间演变的重大不确定性，

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