Carbonate Cementation in Quiet Water Environments: Role of Bacterial-Microalgal Films

安静水环境中的碳酸盐胶结：细菌微藻膜的作用

• 批准号: 9315056
• 负责人: Susan Gaffey
• 金额: $ 19.47万
• 依托单位: Rensselaer Polytechnic Institute
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1994
• 资助国家: 美国
• 起止时间: 1994-02-01 至 1997-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9315056&HistoricalAwards=false
• 关键词: Carbonate; Cementation; Quiet; Water; Environments

9315056 Gaffey Cementation in modern shallow-water marine carbonate sediments is believed to be confined to the intertidal zone, restricted environments with high salinity, and reefs and sand shoals at platform margins. Boring by microbial endoliths, resulting in micritization or destruction of grains, is thought to be the dominant diagenetic process in other shallow marine environments. However, published studies by various workers, and preliminary work by the investigator, indicate that significant volumes of cement are precipitating in low to moderate energy, normal marine phreatic environments, a fact with important implications for cycling and storage of carbonate within protected settings. It is also widely believed that marine cementation is largely a physicochemical process, and that the role of microorganisms in carbonate cementation is restricted to inducing precipitation of carbonate by changing pH and Eh of pore waters. However, sample collection and preparation methods commonly used by sedimentologists degrade or destroy organic structures, so that their role in cementation often goes unrecognized. The proposed work will assess the role of chasmolithic bacteria, cyanobacteria, and microalgae in cementation by using techniques designed to preserve the microbial component of samples intact, and will develop new criteria for recognition of calcified chasmoliths in ancient sediments. In contrast with high energy, platform margin settings, calcification of chasmoliths rather than physicochemical precipitation of carbonate appears to be the dominant cement- forming process in sands from low energy marine phreatic environments. There also appear to be variations in cement types and abundance between different subenvironments within low energy settings. the proposed work will characterize the types and amounts of cements, and their distribution with bioclastic sands in a low, an intermediate, and a high energy lagoon on San Salvador Is land. Bahamas, and relate types and distributions of cements in these three settings to environmental factors such as sea grass cover, wave and current energy, and degree of bioturbation. Characterization of cement types and of their distributions in relation to environmental factors will provide useful criteria for interpreting early diagenetic environments of ancient shallow marine carbonate sediments.

9315056 Gaffey 现代浅水海洋碳酸盐沉积物中的胶结作用被认为仅限于潮间带、高盐度的限制环境以及台缘的礁石和沙滩。 微生物内岩的钻孔导致颗粒微晶化或破坏，被认为是其他浅海环境中的主要成岩过程。 然而，不同工作人员发表的研究以及调查人员的初步工作表明，大量水泥在低至中等能量、正常的海洋潜水环境中沉淀，这一事实对受保护环境中碳酸盐的循环和储存具有重要影响。 人们还普遍认为，海洋胶结在很大程度上是一个物理化学过程，微生物在碳酸盐胶结中的作用仅限于通过改变孔隙水的pH和Eh来诱导碳酸盐沉淀。 然而，沉积学家常用的样品采集和制备方法会降解或破坏有机结构，因此它们在胶结作用中的作用常常被忽视。 拟议的工作将通过使用旨在保存样品中微生物成分完整的技术来评估裂隙细菌、蓝细菌和微藻在胶结中的作用，并将制定识别古代沉积物中钙化裂隙岩的新标准。 与高能量、平台边缘设置相反，碎石的钙化而不是碳酸盐的物理化学沉淀似乎是来自低能量海洋潜水环境的砂中的主要胶结物形成过程。 低能量环境下不同子环境之间的水泥类型和丰度似乎也存在差异。 拟议的工作将描述水泥的类型和数量，以及它们在圣萨尔瓦多岛上的低能、中能和高能泻湖中与生物碎屑砂的分布。 巴哈马，并将这三种环境中水泥的类型和分布与海草覆盖、波浪和海流能量以及生物扰动程度等环境因素联系起来。 胶结物类型及其与环境因素的分布特征将为解释古代浅海碳酸盐沉积物的早期成岩环境提供有用的标准。