A Test of Models for the Evolution of Water-Column Anoxia in the Black Sea Over the Past 8.5 Years

过去8.5年黑海水柱缺氧演变模型的检验

• 批准号: 9628344
• 负责人: Michael Arthur
• 金额: $ 8.5万
• 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: 1997
• 资助国家: 美国
• 起止时间: 1997-02-01 至 1998-08-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9628344&HistoricalAwards=false
• 关键词: Test; Models; Evolution; Water; Column

9628344 Arthur This proposal seeks to resolve a debate as to the intensity and depth distribution of oxygen deficiencies in the water column of the Black Sea and to provide a test of the efficacy of new techniques for elucidating paleoenvironments of ancient "black shales". Previous workers have suggested, on the basis of interpretation of the fabric and geochemical characteristics of sediments deposited from about 8 ka to 2 ka, that finely laminated, organic-carbon (OC) rich sediments of Unit II, often referred to as sapropels, either were deposited under an anoxic water column for which initiation of anoxia was time transgressive, beginning earlier in deeper water, or were produced under an anoxic water column as the result of high surface-water productivity. New results from the study of Black Sea cores recovered during the 1988 R/V Knorr expedition suggest that the onset of water-column anoxia at about 7.5 ka was virtually synchronous across the basin over a depth range of about 200 m to 2250 m, and that anoxia prevailed throughout deposition of Unit II. However, the concentration, accumulation rate, and degree of preservation of organic matter all decreased in the upper part of Unit II, perhaps as a result of decreasing productivity and possible erosion of the top of the chemocline. Various redox-sensitive geochemical indicators have been interpreted by different workers in contrasting ways. In the proposed study, we will use two new techniques, one involving pyrite (framboid) size distributions that constrain the site of pyrite precipitation (water column vs. within sediment), and the other a set of organic biomarker compounds indicative of the presence of photosynthetic sulfide-oxidizing bacteria in the water column. These techniques will be used in analysis of a depth transect of available Black Sea gravity cores that recovered complete sequences of Unit II in order to test models of the Holocene evolution of the Black Sea and the origin(s) of sediments enriched in organic car bon in general.

9628344 Arthur该提案旨在解决有关黑海水柱中氧不足的强度和深度分布的辩论，并为阐明新技术阐明古代“ Black“ Black Sanles”的古环境的功效进行测试。 Previous workers have suggested, on the basis of interpretation of the fabric and geochemical characteristics of sediments deposited from about 8 ka to 2 ka, that finely laminated, organic-carbon (OC) rich sediments of Unit II, often referred to as sapropels, either were deposited under an anoxic water column for which initiation of anoxia was time transgressive, beginning earlier in deeper water, or were produced under an anoxic water column as the高地表水生产率的结果。 在1988年R/V Knorr探险期间回收的黑海核心研究的新结果表明，在约200 m至2250 m的深度范围内，水柱缺氧的发作实际上是在约7.5 ka的情况下同步的，并且在整个单元II的沉积中，缺氧始终存在。 但是，有机物的浓度，积累率和保存程度在II单元的上部都下降了，这可能是由于生产率降低和化学上顶部的可能侵蚀而导致的。 不同工人以对比的方式解释了各种氧化还原敏感的地球化学指标。 在拟议的研究中，我们将使用两种新技术，一种涉及黄铁矿（Framboid）尺寸分布，这些分布限制了黄铁矿沉淀的位点（水柱与沉积物内的水柱），另一种是有机生物标志物化合物，表明存在光合作用的硫化物氧化细菌在水柱中。 这些技术将用于分析可用的黑海重力核心深度样本，该深度核心恢复了II单元的完整序列，以测试黑海的全新世演化模型和一般有机汽车上富含有机汽车的沉积物的起源。