Direct Re-Os Dating of Ordovician Graptolite Biozones: Refining Global Correlations and Earth Time

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。合作研究：奥陶系笔石生物带的直接Re-Os定年：精炼全球相关性和地球时间judith Hannah and J. maletz【摘要】沉积岩沉积的绝对年龄可以通过富碳页岩中有机物质的放射性定年法确定，利用铼（Re）向锇（Os）的衰变。特别是有机壁笔石化石，通常被发现有足够的丰度，可以用Re-Os直接定年。历史上，在广阔的地理空间中，沉积单元的对比依赖于化石组合的比较来确定相对年龄（生物地层学）。大多数基于放射性测年法的年龄只能通过测年更老或更年轻的单位来确定沉积时间。pi们提出，笔石的re - o定年将以与生物地层学相同的分辨率提供准确和精确的年龄，但具有确定绝对时间的未开发优势。地质记录中化石的绝对年龄将确定地质阶段边界和笔石生物带的时间。此外，时间尺度分辨率的提高大大提高了对一系列过程速率的定义，包括沉积、海平面变化、生物演化以及岩石圈板块的垂直和水平运动。pi已经组建了一个多元化的跨学科团队，他们在Re-Os地质年代学、沉积学和富泥系统地层学、笔石分类和古生态学以及构造学方面具有专业知识。PIs将在纽芬兰西部富含笔石的早、中奥陶世沉积层序中放置时间针，以在目前可用的绝对年龄很少的情况下，为奥陶系的一个关键区间提供可靠的年龄控制。此外，在其他几个大陆上也发现了这些相同的笔石组合，这为确定不同地理领域生物进化速度的时间变化提供了可能。进一步发展这一地质年代学工具并证明其在各种条件下的适用性，对石油工业具有直接的利害关系。Re-Os地球化学表明，它有望作为一种示踪剂，将运移的石油与烃源岩联系起来，同时确定运移的时间——这是业内为完善盆地尺度模型而高度寻求的信息。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). Collaborative Research: Direct Re-Os dating of Ordovician graptolite biozones:Refining global correlations and Earth TimeJudith Hannah and J. MaletzColorado State University EAR-0844213AbstractAbsolute ages for the deposition of sedimentary rocks can be determined by radiometric dating of organic material in carbon-rich shales, using the decay of rhenium (Re) to osmium (Os). In particular, fossils of organic-walled graptolites are commonly found in sufficient abundance for direct dating by Re-Os. Historically, correlation of sedimentary units across broad geographic space has relied on comparison of fossil assemblages to establish relative age (biostratigraphy). Most ages based on radiometric dating could only bracket the time of deposition by dating older or younger units. PIs propose that Re-Os dating of graptolites will provide accurate and precise ages at a resolution equal to biostratigraphy, but with the untapped advantage of pinning absolute time. Absolute ages for fossils in the geologic record will fix the time of geologic stage boundaries and graptolite biozones. In addition, increased resolution in the time scale greatly improves the definition of rates for a host of processes, including sedimentation, sea-level change, biologic evolution, and vertical and horizontal motion of lithospheric plates. PIs have assembled a diverse, cross-disciplinary team with expertise in Re-Os geochronology, sedimentology and stratigraphy of mud-rich systems, graptolite taxonomy and paleoecology, and tectonics. PIs will place time pins in the graptolite-rich Early and Middle Ordovician sedimentary sequence in western Newfoundland to provide solid age control in a critical interval of the Ordovician system with few currently available absolute ages. Moreover, these same graptolite assemblages are found on several other continents, opening the potential for defining temporal variations in the rate of biologic evolution in different geographic realms.Further development of this geochronologic tool and demonstration of its applicability under varied conditions is of immediate interest to the petroleum industry. Re-Os geochemistry shows promise as a tracer to link migrated oil with its source rocks, and simultaneously define the time of migration - information highly sought by the industry to refine basin-scale models.