Paleontology, Sedimentology, and Isotopic Geochemistry of the Middle Proterozoic Bangemall Group, Western Australia

西澳大利亚中元古界 Bangemall 群​​的古生物学、沉积学和同位素地球化学

• 批准号: 8817662
• 负责人: Andrew Knoll
• 金额: $ 11万
• 依托单位: Harvard University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1989
• 资助国家: 美国
• 起止时间: 1989-01-15 至 1991-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8817662&HistoricalAwards=false
• 关键词: Paleontology; Sedimentology; Isotopic; Geochemistry; Middle

For the past century, most paleontological research has concentrated on sedimentary rocks deposited over the past 550 million years. It is now clear, however, that this conspicuous record of animals and plants documents only the latest 15% of the history of life on Earth. The earlier (pre-animal) biological record is written in the fossils of microorganisms, as well as in the chemical traces of microbial activity contained in sedimentary rocks. Rocks of Late Proterozoic age (900-550 million years) contain a rich fossil record that includes diverse planktonic algae and seaweeds, as well as bacteria of many kinds. The fossils indicate that this was a period of rapid evolutionary change. Chemical and geological data further suggest that the Late Proterozoic Earth was characterized by major changes in climate, tectonics, atmospheric chemistry, and the cycling of biologically important elements. In contrast, rocks of Early Proterozoic age (2500-1800 million years) reflect a very different world -- one in which an exclusively bacterial biota thrived in environments unaffected by the kinds of climatic and biogeochemical variability seen in the Late Proterozoic era. The key to understanding the transition from the Early Proterozoic Earth to the Late Proterozoic planet clearly must lie in rocks deposited during Middle Proterozoic times (1800- 900 million years). Careful field and laboratory studies will be conducted of the 1400-1300 million year of Bangemall Group, Western Australia -- a suite of rocks especially well suited to yield critical information on biological and environmental change during this period. Field measurements of the thickness, composition, and characteristic features of these rocks will be made; this will permit determination of the age and environmental relationships of the rocks. Samples collected within this matrix will be examined for their microfossil content, rock fabric and alteration history, and geochemistry (especially the ratios of the isotopes of carbon and strontium contained in certain of these rocks). The result will be a multidisciplinary data set that will provide critical insights into Middle Proterozoic biology and environments. Such data are of great importance in efforts to understand life's early evolution and how biology and Earth surface environments have influenced each other through time to produce the modern world. Although this research is basic in nature, it has important applications to mineral and petroleum exploration in Proterozoic rocks. Documentation of fossil and geochemical marker distributions will improve our ability to correlate Proterozoic rocks, the important first step in geological prospecting. A better understanding of Earth's environmental history will additionally serve to constrain patterns of exploration for the rich deposits of stratabound ores locked in Proterozoic sedimentary rocks.

在过去的一个世纪里，大多数古生物学研究都集中在过去 5.5 亿年沉积的沉积岩上。 然而现在很清楚，这些动植物的显着记录仅记录了地球生命历史的最新 15%。 早期（动物出现之前）的生物记录记录在微生物化石以及沉积岩中微生物活动的化学痕迹中。 晚元古代（900-5.5亿年）的岩石含有丰富的化石记录，其中包括多种浮游藻类和海藻，以及多种细菌。 化石表明这是一个快速进化变化的时期。 化学和地质数据进一步表明，晚元古代地球的特点是气候、构造、大气化学和生物重要元素循环的重大变化。 相比之下，早元古代（2500-18亿年）的岩石反映了一个非常不同的世界——在这个世界中，一种独特的细菌生物群在不受元古代晚期气候和生物地球化学变化影响的环境中繁衍生息。 理解早元古代地球向晚元古代行星转变的关键显然在于中元古代（1800-9亿年）沉积的岩石。 将对西澳大利亚班格马尔群（Bangemall Group）的 1400-13 亿年进行仔细的实地和实验室研究，这是一组特别适合提供这一时期生物和环境变化的关键信息的岩石。 将对这些岩石的厚度、成分和特征进行现场测量；这将有助于确定岩石的年龄和环境关系。 将检查在该基质中收集的样本的微化石含量、岩石结构和蚀变历史以及地球化学（特别是某些岩石中所含的碳和锶同位素的比率）。 其结果将是一个多学科数据集，将为中元古代生物学和环境提供重要的见解。 这些数据对于理解生命的早期进化以及生物学和地球表面环境如何随着时间的推移相互影响以产生现代世界非常重要。 尽管这项研究本质上是基础性的，但它对元古界岩石的矿产和石油勘探具有重要的应用。 化石和地球化学标记分布的记录将提高我们关联元古代岩石的能力，这是地质勘探的重要第一步。 更好地了解地球的环境历史还将有助于限制对元古代沉积岩中丰富的层控矿石矿床的勘探模式。