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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Origin of a global carbonate layer deposited in the aftermath of the Cretaceous-Paleogene boundary impact
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Origin of a global carbonate layer deposited in the aftermath of the Cretaceous-Paleogene boundary impact

机译：全球碳酸盐层的起源沉积在白垩纪古近缘边界撞击的后果中

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Microcrystalline calcite (micrite) dominates the sedimentary record of the aftermath of the Cretaceous-Paleogene (K-Pg) impact at 31 sites globally, with records ranging from the deep ocean to the Chicxulub impact crater, over intervals ranging from a few centimeters to more than seventeen meters. This micriterich layer provides important information about the chemistry and biology of the oceans after the impact. Detailed high-resolution scanning electron microscopy demonstrates that the layer contains abundant calcite crystals in the micron size range with a variety of forms. Crystals are often constructed of delicate, oriented agglomerates of sub-micrometer mesocrystals indicative of rapid precipitation. We compare the form of crystals with natural and experimental calcite to shed light on their origin. Close to the crater, a significant part of the micrite may derive from the initial backreaction of CaO vaporized during impact. In more distal sites, simple interlocking rhombohedral crystals resemble calcite precipitated from solution. Globally, we found unique calcite crystals associated with fossilized extracellular materials that strikingly resemble calcite precipitated by various types of bacteria in natural and laboratory settings. The micrite-rich layer contains abundant bacterial and eukaryotic algal biomarkers and most likely represents global microbial blooms initiated within millennia of the K-Pg mass extinction. Cyanobacteria and non-haptophyte microalgae likely proliferated as dominant primary producers in cold immediate post-impact environments. As surface-water saturation state rose over the following millennia due to the loss of eukaryotic carbonate producers and continuing river input of alkalinity, "whitings" induced by cyanobacteria replaced calcareous nannoplankton as major carbonate producers. We postulate that the blooms grew in supersaturated surface waters as evidenced by crystals that resemble calcite precipitates from solution. The microbial biomass may have served as a food source enabling survival of a portion of the marine biota, ultimately including life on the deep seafloor. Although the dominance of cyanobacterial and algal photosynthesis would have weakened the biological pump, it still would have removed sufficient nutrients from surface waters thus conditioning the ocean for the recovery of biota at higher trophic levels. (C) 2020 Elsevier B.V. All rights reserved.
机译：微晶方解石（Micrite）主导了在全球31个站点的白垩纪 - 古常（K-PG）影响的沉积记录，从深海到螯合冲击火山口的记录，间隔从几厘米到更多比十七米。此Micriterich层提供了有关冲击后海洋化学和生物学的重要信息。详细的高分辨率扫描电子显微镜表明该层含有各种形式的微米尺寸范围内的丰富方解石晶体。晶体通常由指示快速沉淀的亚微米晶体的精细，取向的附聚物构成。我们将晶体的形式与自然和实验性方解石进行比较，以阐明它们的起源。靠近火山口，显微部的重要部分可以从撞击过程中蒸发的初始反应。在更多远端部位，简单的互锁菱形晶体类似于溶液沉淀的方解石。在全球范围内，我们找到了与僵化的细胞外材料相关的独特方解石晶体，其在天然和实验室环境中通过各种细菌沉淀出来的脑脱毛。富含微粒和真核藻类生物标志物的微生物和真核藻类生物标志物最有可能代表在K-PG质量灭绝的千年内启动的全局微生物绽放。蓝细菌和非触觉微藻可能在冷的立即影响环境中作为占优势初级生产者的增殖。由于表面 - 水饱和状态由于真核碳酸酯生产商的丧失和碱度的持续河流的丧失而导致的表面水饱和状态升高，由Cyanobacteria诱导的钙质甘露糖蛋白诱导为主要碳酸盐生产商。我们假设绽放在超饱和表面水中增长，如晶体从溶液中沉淀的晶体所证明的。微生物生物量可能已经用作能够生存一部分海洋生物群的食物来源，最终包括在深海地板上的生命。虽然蓝藻和藻类光合作用的优势将削弱生物泵，但它仍然会从表面水域中消除足够的营养素，从而调节海洋以在更高的营养水平下恢复生物群。 （c）2020 Elsevier B.v.保留所有权利。

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