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

该项目将对将于2004年夏天获得的新收集的太古宙沉积物钻芯进行地质、古生物和地球化学检查。这个连续的岩芯长约1000米，将对西澳大利亚皮尔巴拉克拉通哈默斯利盆地最后约2.5亿年的太古宙地层进行采样。采样的岩性将包括玄武岩、碳酸盐、硅质岩和几个干酪生黄铁矿页岩单元。这一提议是可能的，因为与NASA天体生物研究所的天体生物钻探计划(ADP)合作的机会前所未有。ADP将为收购这一核心提供资金。美国国家科学基金会的资金将用于岩心物质的初步表征，包括对煤质沉积物中的古生态和古环境进行详细研究。重要的是，岩心回收将由皮别克监督，并专门针对拟议的研究。智力价值：拟议的研究的总体动机是描述太古宙晚期的生命及其环境的特征，就在大气氧气上升前不久。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期在内的同期气候振荡的关系。该团队的兴趣是了解太古宙生物圈是如何为这种独特的环境变化奠定基础的，这一兴趣略有不同，但具有互补性。具体地说，该项目的一个主要目标是表征晚太古代海洋环境中不同类型微生物的相对重要性，并通过岩相关系来研究环境对其分布的控制。这一目标将通过对煤质沉积物中的碳氢分子生物标志物、氧化还原指示剂和生物地球化学循环的综合检查来实现。清洁的钻井方法、立即采样和及时分析将使我们能够明确地确定这些岩石是否含有分类学诊断的甾烷和三萜烃。这些化合物在现有的保存完好的哈默斯利盆地钻探岩心中含量丰富，如果不是污染物，也是真核生物和蓝藻最早的生物标志物。此外，对新核心的分析应使我们能够在环境背景下检查这些化合物的相对丰度和同位素组成，从而产生关于生态关系的信息。其他目标是确定晚太古宙主要生物地球化学旋回的状况，并通过对整个岩芯进行沉积学和生物地球化学勘察，为未来的调查建立可靠的基线。总而言之，这项工作将检验一种假设，即太古宙生态系统中存在产氧蓝藻和好氧微生物，这些代谢作用的环境印记在它们起源后的数亿年里仍然保持沉默。广泛影响：有三个更广泛的影响领域。首先，约6名研究生将参与一个跨越六所主要研究型大学的非同寻常的综合性和多学科研究项目。虽然每个学生都将植根于该项目的一个方面，但这些学生将有大量机会跨越各个子学科和机构。其次，由于计划中的钻探岩芯最终将根据ADP章程公开提供，这项工作将为更广泛的研究界提供一个有益于岩性和化学地层的框架。第三，希望NSF和NASA的这一合作将为其他调查人员未来的努力提供积极的先例，这些努力最终可能演变为更广泛的机构间“深部时间钻探计划”。

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".