COLLABORATIVE RESEARCH: Geochemical and Isotopic Constraints on Mesproterozoic Ocean Chemistry Working Toward a Global Perspective

合作研究：中元古代海洋化学的地球化学和同位素约束面向全球视角

• 批准号: 9725397
• 负责人: Tracy Frank
• 金额: $ 2.61万
• 依托单位: Pennsylvania State Univ University Park
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-01-15 至 1999-06-09
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9725397&HistoricalAwards=false
• 关键词: COLLABORATIVE; RESEARCH; Geochemical; Isotopic; Constraints

9725397 Frank The Mesoproterozoic Eon (1600-1000 Ma) represents a critical period in Earth history from the standpoint of eukaryotic diversification (Knoll, 1991), fundamental transitions in the oxidation state of the Earth's atmosphere and oceans (Des Marais et al., 1992; Canfield and Teske, 1996), and global tectonic reorganization (Dalziel, 1991). Yet despite this obvious significance, the Mesoproterozoic remains one of the most poorly understood and poorly documented intervals in Earth history. For example, in reference to an apparent stability in the Mesoproterozoic marine carbon isotopic record, the era between 1600 Ma and 1000 Ma has been reported as 'the dullest time in Earth's history' (Buick et al., 1995). However, a large positive shift (3-4%) in marine carbonate (13C values has recently been recognized in late Mesoproterozoic (1300 Ma) successions from Siberia, Arctic Canada, Greenland, and the United States. Rather than a short-lived excursion, this shift appears to represent a prolonged and fundamental change that may represent a significant transition in the Earth's global carbon cycle. The timing of this observed transition, between ~1300 and ~1150 Ma, is particularly intriguing in that it occurs in conjunction with the early assembly of the Rodinian supercontinent and a purported rise in the concentration of atmospheric oxygen. The goal of the proposed research is to generate carbon, sulfur and strontium isotopic data for this interval and, thereby, document and begin to address mechanistically the most fundamental (first-order) shifts in the chemistry of the Mesoproterozoic ocean. These objectives will be achieved through a multidisciplinary study that integrates depositional, diagenetic, and geochemical information into a single comprehensive framework. Although no single stratigraphic succession adequately encompasses the interval surrounding the observed carbon isotopic shift, two distinct successions (Society Cliffs Formation, northern Baffin Island; Dismal L akes Group, Coppermine homocline, Northwest Territories) can be effectively spliced to provide coverage across the interval of the observed transition. Each of these successions has been chosen on the basis of accessibility and exposure of stratigraphic units, the presence of a wide variety of facies and lithologies suitable for geochemical analysis, and the abundance of a variety of allochems and marine cements from different depositional environments. Combined, these prerequisites assure recognition of depositional and diagenetic trends that would otherwise hamper the interpretation of geochemical and isotopic data. Such an integrated approach will provide the clearest path toward understanding the complex evolution of the Proterozoic biosphere.

9725397 Frank The Mesoproterozoic Eon (1600-1000 Ma) represents a critical period in Earth history from the standpoint of eukaryotic diversification (Knoll, 1991), fundamental transitions in the oxidation state of the Earth's atmosphere and oceans (Des Marais et al., 1992; Canfield and Teske, 1996), and global tectonic reorganization (Dalziel, 1991). 然而，尽管具有显而易见的意义，但中元仍然是地球历史上最糟糕的间隔之一。 例如，指的是中古代海洋碳同位素记录的明显稳定性，据报道，1600 Ma和1000 MA之间的时代已被报道为“地球历史上最乏味的时间”（Buick等，1995）。 然而，海洋碳酸盐的巨大转变（最近已经在中间龙仓晚期（1300 ma）的继任中得到认可（13C值），从西伯利亚，北极加拿大，格陵兰岛和美国认识到。而不是短暂的旅行。这种转变似乎代表了这一延长和基本变化，这可能代表了地球上的重大转变。 〜1150 Ma特别有趣，因为它与罗丹尼亚超级大陆的早期组装结合，并且所提出的研究的目的是产生碳，硫和层的同位素数据，并在此间隔（首先是，从而开始依次），该研究的目的是产生碳，硫和金腹的数据。中元的海洋将通过一项多学科研究来实现，该研究将沉积，成岩和地球化学信息整合到一个全面的框架中。西北地区可以有效地拼接，以在观察到的过渡的间隔内提供覆盖范围。沉积和成岩趋势否则会阻碍地球化学和同位素数据的解释。