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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Biologically induced initiation of Neoproterozoic snowball-Earth events
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Biologically induced initiation of Neoproterozoic snowball-Earth events

机译：新元古代雪球地球事件的生物诱导引发

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摘要

The glaciations of the Neoproterozoic Era (1,000 to 542 MyBP) were preceded by dramatically light C isotopic excursions preserved in preglacial deposits. Standard explanations of these excursions involve remineralization of isotopically light organic matter and imply strong enhancement of atmospheric CO2 greenhouse gas concentration, apparently inconsistent with the glaciations that followed. We examine a scenario in which the isotopic signal, as well as the global glaciation, result from enhanced export of organic matter from the upper ocean into anoxic subsurface waters and sediments. The organic matter undergoes anoxic remineralization at depth via either sulfate- or iron-reducing bacteria. In both cases, this can lead to changes in carbonate alkalinity and dissolved inorganic pool that efficiently lower the atmospheric CO2 concentration, possibly plunging Earth into an ice age. This scenario predicts enhanced deposition of calcium carbonate, the formation of siderite, and an increase in ocean pH, all of which are consistent with recent observations. Late Neoproterozoic diversification of marine eukaryotes may have facilitated the episodic enhancement of export of organic matter from the upper ocean, by causing a greater proportion of organic matter to be partitioned as paniculate aggregates that can sink more efficiently, via increased cell size, biomineralization or increased C:N of eukaryotic phytoplank-ton. The scenario explains isotopic excursions that are correlated or uncorrelated with snowball initiation, and suggests that increasing atmospheric oxygen concentrations and a progressive oxygenation of the subsurface ocean helped to prevent snowball glaciation on the Phanerozoic Earth.
机译：在新元古代时代（1000至542 MyBP）的冰川期之前，保存在冰川前沉积物中的轻度C同位素漂移很明显。这些游览的标准解释包括同位素轻质有机物的再矿化和暗示大气中二氧化碳温室气体浓度的显着提高，这显然与随后的冰川活动不一致。我们研究了一种情景，在该情景中，同位素信号以及全球冰川活动是由于有机物从上层海洋向缺氧地下水和沉积物的出口增加所致。有机物通过硫酸盐还原或铁还原细菌在深度进行缺氧再矿化。在这两种情况下，这都可能导致碳酸盐碱度和溶解的无机物池变化，从而有效降低大气中的二氧化碳浓度，从而可能使地球陷入冰河时期。这种情况预示着碳酸钙的沉积增加，菱铁矿的形成以及海洋pH值的增加，所有这些都与最近的观察结果一致。晚期新元古代海洋真核生物的多样化可能通过使较大比例的有机物分配为可通过增加细胞大小，生物矿化或增加而更有效地下沉的颗粒状聚集体，从而促进了从上层海洋中有机物出口的激增。真核浮游植物的C：N。该场景说明了与雪球引发相关或不相关的同位素漂移，并表明增加的大气中氧气浓度和地下海洋的逐步充氧有助于防止幻雪在地球上的冰川化。

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    Eli Tziperman; Itay Halevy; David T. Johnston; Andrew H. Knoll; Daniel P. Schrag;

  • 作者单位

    Department of Earth and Planetary Sciences, Harvard University, 20 Oxford Street, Cambridge, MA 02138;

    Division of Geological and Planetary Sciences, California Institute of Technology, MC 100-23, 1200 East California Boulevard, Pasadena, CA 91125;

    Department of Earth and Planetary Sciences, Harvard University, 20 Oxford Street, Cambridge, MA 02138;

    Department of Earth and Planetary Sciences, Harvard University, 20 Oxford Street, Cambridge, MA 02138;

    Department of Earth and Planetary Sciences, Harvard University, 20 Oxford Street, Cambridge, MA 02138;

  • 收录信息 美国《科学引文索引》(SCI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    carbon isotopes; co2;

    机译：碳同位素;二氧化碳;

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