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

在过去的一个世纪里，大多数古生物研究集中在过去5.5亿年前沉积的沉积岩上。然而，现在很清楚的是，这一引人注目的动植物记录只记录了地球上生命历史的最新15%。更早的(动物前)生物记录被记录在微生物的化石中，以及沉积岩中包含的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，其中包括各种浮游藻类和海藻，以及多种细菌。这些化石表明，这是一个快速进化的时期。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的循环发生了重大变化。相比之下，早元古代(2500-1.8亿年)的岩石反映了一个非常不同的世界--在这个世界里，只有细菌生物群在不受晚元古代气候和生物地球化学变化影响的环境中茁壮成长。理解早元古代地球向晚元古代地球过渡的关键显然在于中元古代(1800-9亿年)沉积的岩石。将对西澳大利亚州邦戈马尔集团1400-1300亿年进行仔细的野外和实验室研究--这是一套特别适合提供有关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。在该基质中收集的样品将被检查其微化石含量、岩石组构和蚀变历史以及地球化学(特别是某些岩石中所含碳和锶的同位素比率)。其结果将是一个多学科的数据集，将提供对中元古代生物学和环境的关键见解。这些数据对于了解生命的早期进化以及生物和地球表面环境如何随着时间的推移相互影响而形成现代世界具有重要意义。虽然这项研究是基础性的，但它在元古界岩石的矿产和石油勘探中具有重要的应用。化石和地球化学标志分布的记录将提高我们对比元古界岩石的能力，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元古代沉积岩中层控矿石丰富矿藏的勘探模式。

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.