Fingerprinting and Calibrating Low Oxygen Conditions Using Vanadium Isotopes

在海洋沉积物中发现、测试和开发化学代用品（遗迹材料），以揭示地球地质历史中近地表环境条件的强氧化或弱氧化程度，这对于理解海洋化学、生物进化和灭绝以及气候之间的相互作用非常重要。迄今为止，科学家们还没有一个低氧但非零氧条件的替代品——这种条件很可能在地球历史上重要的生物时期占据主导地位。在这个项目中，研究人员将在现代海洋的一系列氧气条件下研究底水氧浓度与痕量金属钒(V)同位素之间的关系。基于试验数据、理论计算和溶解的海水V浓度，他们认为岩心顶部沉积物的稳定V同位素比率将在一系列底水氧气条件下系统地相关。通过分析这些材料，研究小组希望建立V同位素与底水氧浓度之间的关系。考虑到化学代用物对量化过去气候变化的重要性，这项研究的结果对现代和古海洋学界以及建模者更好地了解地球历史上广泛的氧变化具有重要意义。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，但在了解整个地球历史上的低氧条件方面仍存在重大差距。因此，开发新的古氧化还原代用物，为这些重要的地球历史时期的海洋氧化还原条件提供额外和补充的知识是非常重要的。在这项研究中，科学家将分析大块沉积物及其有机和锰铁矿物组分，以研究不同沉积组分中的V同位素变化。（由于底水氧浓度的差异，这些样品包括富有机到富锰铁的沉积物。）利用钒同位素重建海洋低氧环境将填补古氧化还原代工具箱的空白。为了能够将钒同位素作为准确的古氧化还原指标，需要对现代沉积物中的V同位素变化进行开发、校准和指纹化。

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.