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首页> 外文期刊>Paleoceanography >Astronomically Driven Variations in Depositional Environments in the South Atlantic During the Early Cretaceous
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Astronomically Driven Variations in Depositional Environments in the South Atlantic During the Early Cretaceous

机译：白垩纪南大西洋沉积环境中的天文驱动的变化

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The extent and persistence of anoxia in the South Atlantic Ocean during its early opening phase in the Early Cretaceous is not well constrained, hindering a holistic understanding of the processes and mechanisms that drive past changes in water column redox conditions, as well as the impacts of such changes on marine ecosystems. Here we provide high-resolution geochemical records from Deep Sea Drilling Project Site 364 that document variations in redox conditions, chemocline depth, marine productivity, and marine ecosystem dynamics in the northern South Atlantic during the Aptian. We show that many of these parameters varied across discrete sedimentary cycles expressed in the Deep Sea Drilling Project 364 succession. Our data indicate that during the initial stages of basin development, anoxic and euxinic conditions were prevalent and occasionally extended into the upper water column. However, strong cyclicity in sedimentological and geochemical parameters imply that the anoxia/euxinia was not a persistent state. We argue that the water column redox conditions during the Aptian were driven by changes in the hydrological cycle, induced by variations in astronomical forcing. We suggest that the episodically amplified hydrological cycle not only enhanced nutrient availability and marine productivity, but might also have caused density-driven upper ocean stratification. The presence of black shales of similar age in other ocean basins suggests that this mechanism is broadly important for the formation of Early Cretaceous organic-rich successions.
机译：南大西洋在早期白垩纪早期开放期间缺氧的程度和持续性并不受到很大的限制，阻碍了对越过水柱氧化还原条件的流动变化的过程和机制以及影响的整体理解海洋生态系统的这种变化。在这里，我们提供来自深海钻探项目现场364的高分辨率地球化学记录，在安踏期间南大西洋北部大西洋的氧化还原条件，化学系列，海洋生产力和海洋生态系统动态的文献变化。我们表明，许多这些参数在深海钻探项目364连续的离散沉积循环中变化。我们的数据表明，在盆地发育的初始阶段，缺氧和迅速的条件普遍存在，偶尔延伸到上水柱中。然而，沉积物和地球化学参数的强烈循环意味着缺氧/ exinia不是持续状态。我们认为，APTIAN期间的水柱氧化还原条件是由水文循环的变化驱动的，通过天文迫使的变化诱导。我们建议，整容性放大的水文循环不仅提高了营养可用性和海洋生产力，而且也可能引起了密度驱动的上海分层。其他海洋盆地在其他海洋盆地的黑色神话的存在表明这种机制对于形成早期的白垩纪有机化的演替是非常重要的。

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