COLLABORATIVE RESEARCH: Presaging Paleoproterozoic Global Change: Geobiology of the Late Archean Eon

该项目将对2004年夏季新采集的太古代沉积物岩心进行综合地质、古生物和地球化学研究。这一长度约为1000米的连续岩心将对西澳大利亚皮尔巴拉盆地哈默斯利盆地最近2.5亿年的太古代地层进行取样。取样的岩性将包括玄武岩、碳酸盐岩、燧石和几个干酪根黄铁矿页岩单元，这一建议之所以成为可能，是因为与美国航天局天体生物学研究所天体生物学钻探方案有了前所未有的合作机会。ADP将为该核心的收购提供资金。国家科学基金会的资金将用于初步鉴定岩心材料，包括详细研究干酪根沉积物中的古生态学和古环境。重要的是，核心恢复将由PI别克监督，并专门针对拟议的research.Intellectual优点：拟议的研究的一般动机是描述生命的性质和环境在太古代晚期，不久之前，大气中的氧气上升。许多研究人员正在研究这种氧化还原转变的时间，以及它与可能包括全球冰河时代在内的同期气候振荡的关系。该团队的兴趣，有点不同，但互补，是了解太古代生物圈如何为这种独特的环境转变奠定基础。该项目的一个主要目标是确定不同类型微生物在晚太古代海洋环境中的相对重要性，并通过岩相关系研究环境对其分布的控制。通过对干酪根沉积物中烃类分子生物标志物、氧化还原指示物和生物地球化学循环的综合研究，清洁钻井方法、即时取样和快速分析将使我们能够明确地确定这些岩石中是否存在具有分类学诊断意义的甾烷和三萜类烃。这些化合物在现有的、保存较差的哈默斯利盆地钻孔岩芯中含量丰富，如果不是污染物，则构成了真核生物和蓝藻的最早生物标志物。此外，分析新的核心应该允许我们检查的相对丰度和同位素组成的化合物在环境背景下，产生有关生态关系的信息。其他目标是描述太古代晚期主要地球化学循环的特征，并通过对整个岩芯进行沉积学和地球化学勘测，为未来的调查提供一个可靠的基线。总的来说，这项工作将测试的假设，即产氧蓝藻和好氧微生物存在于太古代生态系统，这些metabolisms的环境印记保持沉默了数亿年后，他们的起源。更广泛的影响：有三个领域的更广泛的影响。首先，约6名研究生将参加一个跨越六所主要研究型大学的综合性和多学科研究项目。虽然每个人都将扎根于该计划的一个方面，这些学生将有大量的机会跨越学科和机构。其次，由于计划中的岩心最终将根据ADP章程公开提供，这项工作将为更广泛的研究界提供有益的岩性和化学地层框架。第三，希望NSF和NASA的合作将为其他研究人员的未来努力提供一个积极的先例，最终可能演变成一个更广泛的跨机构“深时钻探计划”。

Project will integrate geological, paleobiological and geochemical examination of a freshly-collected Archean sediment drill-core that will be obtained in the summer of 2004. This continuous core, ~ 1000 m in length, will sample the last ~ 250 million years of Archean stratigraphy in the Hamersley Basin of the Pilbara Craton, Western Australia. Sampled lithologies will include basalt, carbonate, chert and several kerogenous pyritic shale units.This proposal is possible because of an unprecedented opportunity for collaboration with the Astrobiology Drilling Program (ADP) of the NASA Astrobiology Institute. The ADP will fund acquisition of this core. The NSF funds will be used for initial characterization of core materials to include a detailed study of paleoecology and paleoenvironment in kerogenous sediments. Importantly, core recovery will be over-seen by PI Buick and is geared specifically toward the proposed research.Intellectual Merit: The general motivation of the proposed research is to characterize the nature of life and its environment in the late Archean, shortly before the rise of atmospheric oxygen. Many workers are examining the timing of this redox transition and its relationship to contemporaneous climatic oscillations that may include global ice ages. The team's interest, somewhat different but complementary, is to understand how the Archean biosphere set the stage for this singular environmental transformation. Specifically, a major goal of this project is to characterize the relative importance of different types of microbes in late Archean marine environments and, through lithofacies relationships, to study the envi-ronmental controls on their distributions. This goal will be achieved through integrated examination of hydrocarbon molecular biomarkers, redox indicators and biogeochemical cycling in kerogenous sediments.Clean drilling methods, immediate sampling and prompt analysis will allow us to unambiguously deter-mine if taxonomically diagnostic sterane and triterpenoid hydrocarbons are indigenous to these rocks. These compounds are abundant in existing, poorly-preserved Hamersley Basin drill core and, if not contaminants, constitute the earliest biomarkers of eukaryotes and cyanobacteria. Further, analysis of the new core should permit us to examine the relative abundances and isotopic compositions of such compounds in an environmental context, yielding information about ecological relationships. Additional goals are to characterize the status of major biogeochemical cycles in the late Archean and generate a robust baseline for future investigations by conducting sedimentological and biogeochemical reconnaissance of the entire core. Collectively, this work will test the hypothesis that oxygen-generating cyanobacteria and aerobic microorganisms were present in Archean ecosystems and that the environmental imprints of these me-tabolisms remained muted for hundreds of millions of years after their origins.Broader Impact: There are three areas of broader impact. First, ~ 6 graduate students will participate in an unusually integrative and multi-disciplinary research project spanning six major research universities. While each will be rooted in a single aspect of the program, these students will have substantive opportunities to bridge across subdisciplines and institutions. Second, because the planned drill core will ultimately be openly available in accordance with the ADP charter, this work will provide a lithological and chemostratigraphic framework of benefit to the wider research community. Third, it is hoped that this NSF-NASA collaboration will provide a positive precedent for future efforts by other investigators that might ultimately evolve into a broader inter-agency "Deep Time Drilling Program".