Characterizing mantle input during the Cenomanian/Turonian oceanic anoxic event using osmium isotopes

使用锇同位素表征塞诺曼阶/土伦阶海洋缺氧事件期间的地幔输入

• 批准号: NE/G009678/1
• 负责人: David Selby
• 金额: $ 4.52万
• 依托单位: Durham University
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2009
• 资助国家: 英国
• 起止时间: 2009 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FG009678%2F1
• 关键词: Characterizing; mantle; input; during; Cenomanian

The fundamental goal of Earth Science is to reconstruct geologic history in order to understand how past events have shaped the evolution of planet Earth. Rock deposits from the Earths ancient oceans hold clues to the past events. The Earth's history periodically records evidence that the ocean's abruptly become depleted in oxygen (anoxic) for short periods of time (0.5 to 1 million years). It is believed oceanic anoxic events are linked to lapses in key oceanic current circulations, climate perturbations, and/or intense magmatic activity that have resulted in the deposition of black carbon-rich rocks. The causes of these global oceanic anoxic events remain a hotly debated topic and resolution of the problem will have profound implications for our understanding of why oceanic anoxic events are common just to the Cretaceous. One specific oceanic anoxic event we propose to study occurred 93.5 million years ago at the boundary of the Cenomanian-Turonian geologic time stages. Geoscientists who study ancient oceans rely on chemical signals in oceanic sediment to reconstruct oceanic processes and environments, for example isotopes of carbon, oxygen and strontium. Isotopes of osmium determined from oceanic sediments can also be used, whereby they monitor changes in the input and flux of continental weathering and magmatic activity in to the oceans. Our current understanding suggests that the Earth 93.5 million years ago had a similar plate tectonic structure to today's Earth for which we have well established ocean current circulation paths and a single osmium isotope composition that suggests that osmium is predominantly derived from detritus from the Earth's crust. However, just prior to the Cenomanian-Turonian boundary oceanic anoxic event a recent study suggests that osmium in the oceans is sourced from intense magmatic activity, which may have triggered a global oceanic anoxic event. However, osmium isotope values from two sections we have studied compared to this recent study show that these time-correlative values are disparate, suggesting that the osmium isotope budget in the ocean was drastically different. Thus very unlike today's ocean. As a result this raises an important question: can osmium isotope values from one location, which researchers have relied on thus far, be used to interpret global processes? Detailed osmium isotope analysis across two global sections will aid in defining a comprehensive understanding of the osmium isotope homogeneity in the ocean during the Cenomanian-Turonian boundary oceanic anoxic event. This will permit an improved understanding of individual oceanic areas (e.g., inputs into the ocean and weathering rates) and global ocean currents. As a direct result the research will test the hypothesis of whether magamtic activity triggered the cause of global oceanic anoxia. Especially significant is that the outcome of the proposed study will benefit researchers who are investigating the ocean to understand the Earths evolution.

地球科学的基本目标是重建地质历史，以了解过去的事件如何塑造地球的演变。来自地球古代海洋的岩石沉积物为过去的事件提供了线索。地球的历史周期性地记录了海洋在短时间内（0.5至100万年）突然耗尽氧气（缺氧）的证据。据信，海洋缺氧事件与关键洋流环流、气候扰动和/或导致黑色富碳岩石沉积的强烈岩浆活动有关。这些全球海洋缺氧事件的原因仍然是一个激烈争论的话题，解决这个问题将对我们理解为什么海洋缺氧事件在白垩纪很常见产生深远的影响。我们建议研究的一个特定的海洋缺氧事件发生在9350万年前的Cenomanian-Turonian地质时代的边界。研究古代海洋的地球科学家依靠海洋沉积物中的化学信号来重建海洋过程和环境，例如碳，氧和锶的同位素。从海洋沉积物中测定的锇同位素也可用于监测大陆风化和岩浆活动输入和流入海洋的变化。我们目前的理解表明，9350万年前的地球具有与今天地球相似的板块构造结构，我们已经确定了洋流循环路径和单一的锇同位素组成，这表明锇主要来自地壳的碎屑。然而，就在Cenomanian-Turonian边界海洋缺氧事件之前，最近的一项研究表明，海洋中的锇来源于强烈的岩浆活动，这可能引发了全球海洋缺氧事件。然而，我们研究的两个部分的锇同位素值与最近的研究相比表明，这些时间相关的值是不同的，这表明海洋中的锇同位素预算是截然不同的。与今天的海洋非常不同。因此，这就提出了一个重要的问题：研究人员迄今所依赖的来自一个地点的锇同位素值是否可以用来解释全球过程？详细的锇同位素分析在两个全球部分将有助于确定在海洋中的锇同位素均匀性的全面了解在Cenomanian-Turonian边界海洋缺氧事件。这将有助于更好地了解个别海洋区域（例如，输入到海洋和风化率）和全球洋流。作为直接结果，这项研究将检验岩浆活动是否引发了全球海洋缺氧的假设。特别重要的是，拟议研究的结果将有利于研究海洋以了解地球演变的研究人员。

项目成果

Marine 187Os/188Os isotope stratigraphy reveals the interaction of volcanism and ocean circulation during Oceanic Anoxic Event 2

• DOI: 10.1016/j.epsl.2013.12.024
• 发表时间: 2014-03-01
• 期刊: EARTH AND PLANETARY SCIENCE LETTERS
• 影响因子: 5.3
• 作者: Du Vivier, Alice D. C.;Selby, David;Voigt, Silke
• 通讯作者: Voigt, Silke

Ca isotope stratigraphy across the Cenomanian-Turonian OAE 2: Links between volcanism, seawater geochemistry, and the carbonate fractionation factor

• DOI: 10.1016/j.epsl.2015.02.001
• 发表时间: 2015-04-15
• 期刊: EARTH AND PLANETARY SCIENCE LETTERS
• 影响因子: 5.3
• 作者: Du Vivier, Alice D. C.;Jacobson, Andrew D.;Sageman, Bradley B.
• 通讯作者: Sageman, Bradley B.