Fingerprinting and Calibrating Low Oxygen Conditions Using Vanadium Isotopes

在海洋沉积物中发现、测试和开发化学替代物(遗迹材料)，揭示地球地质历史上近地表环境条件的氧化程度或强或弱，对于理解海洋化学、生物进化和灭绝与气候之间的相互作用极其重要。到目前为止，科学家们还没有一个代表低氧但非零氧气的条件--这种条件很可能在地球历史上具有重要生物学意义的时期占据主导地位。在这个项目中，研究人员将研究现代海洋中各种氧气条件下底层水氧浓度与痕量金属钒(V)的同位素之间的关系。根据试点数据、理论计算和溶解的海水钒浓度，他们认为，岩心顶部沉积物中稳定的钒同位素比率将在一系列底层水氧条件下系统地相互关联。通过分析这些材料，研究小组希望建立V同位素和底层水氧浓度之间的关系。考虑到化学替代物在量化过去气候变化方面的重要性，这项研究的结果将对现代和古海洋学界以及建模人员更好地理解地球历史上广泛的氧气变异性具有重要意义。尽管最近的研究提供了关于古代海洋氧化还原条件的丰富信息，但在整个地球历史上，对低氧条件的理解存在着显著的差距。因此，重要的是开发新的古氧化还原替代物，能够在地球历史的这些重要时期提供关于海洋氧化还原条件的额外和补充知识。在这项研究中，科学家们将分析大宗沉积物及其有机和锰铁矿物组分，以调查不同沉积组分中的V同位素变异性。(由于底水含氧量不同，这些样品由富有机到富含铁锰的沉积物组成。)使用钒同位素重建海洋低氧条件将填补古氧化还原代理工具箱中的空白。开发、校准和指纹化现代沉积物中的V同位素变异性，需要能够应用钒同位素作为准确的古氧化还原替代物。

Discovering, testing, and developing chemical proxies (relic materials) in marine sediments that reveal how strongly or weakly oxidizing near-surface environmental conditions were in the Earth's geological past are immensely important for understanding interactions between ocean chemistry, biological evolution and extinctions, and climate. To date scientists do not have a proxy for low but non-zero oxygen conditions -- the sort of conditions that are likely to have dominated in biologically important periods of Earth history. In this project, researchers will study the relationship between bottom water oxygen concentration and the isotopes of the trace metal vanadium (V) in a range of oxygen conditions in the modern ocean. Based on pilot data, theoretical calculations and dissolved seawater V concentrations they believe that stable V isotope ratios of core top sediments will correlate systematically over a range of bottom water oxygen conditions. By analyzing these materials, the research team expects to establish the relationship between V isotopes and bottom water oxygen concentrations. Given the importance of chemical proxies to quantify past climate change, the results of this study will be of great importance to the modern and paleoceanographic community, as well as for modelers to better understand a broad range of oxygen variability in Earth history.Although recent investigations have provided a wealth of information about the redox conditions of the ancient oceans, there is a significant gap in understanding low oxygen conditions throughout Earth history. Therefore, it is important to develop new paleoredox proxies that can provide additional and complementary knowledge about ocean redox conditions during these important periods of Earth history. In this study, scientists will analyze bulk sediments and their organic and ferromanganese mineral fractions to investigate the V isotopic variability within the various sedimentary components. (These samples comprise organic rich to ferromanganese rich sediments due to a range in bottom water oxygen concentrations.) Reconstructing marine low oxygen conditions using vanadium isotopes would fill a void in the paleoredox proxy toolbox. Developing, calibrating, and fingerprinting the V isotopic variability in modern sediments is required to be able to apply vanadium isotopes as an accurate paleoredox proxy.