Collaborative Research: Isotopic, Geochronologic, and Tectonic Character of the Western Piedmont, Virginia - Implications for the Closing of Iapetus

Iapetus洋是早古生代的一级海洋带，它将北美东部与冈瓦南周边的地壳块体分开。它的关闭，将北美与阿巴拉契亚山脉的这些广域元素并列在一起，给全球水圈和大气施加了新的循环机制，这是朝着最终合并泛大陆的超大陆迈出的重要一步。尽管Iapetus在全球古生代演化中具有重要意义，但人们对其关闭的时间和性质知之甚少，主要是因为北美和冈瓦纳元素之间的原始界面，即主要的Iapetus缝合线，在美国阿巴拉契亚山脉尚未被发现。根据区域地质关系和缺乏的同位素资料，假设弗吉尼亚州中部的Chopawamsic断裂代表了美国阿巴拉契亚山脉的主要Iapetan缝合线。该项目通过整合断层两侧岩浆岩的Nd-和Pb-同位素研究结果来验证这一假设；通过对断层两侧及断层上方地层碎屑锆石种群的U-Pb锆石年代学研究；通过对选定的岩浆单元进行高分辨率U-Pb年代学分析，并对断层进行运动学和年代学分析。这项研究是北卡罗来纳州立大学和德克萨斯农工大学的研究人员共同努力的结果。阿巴拉契亚地质管理着北美人口最稠密的地区的资源（矿物、水），并影响着人们的健康（地震灾害）；从逻辑上讲，对基岩地质的基本了解对该地区的进一步开发和可持续发展至关重要。这项研究的结果也将采取多种途径进入更广泛的教育和推广领域。该项目部分资助了8名学生，其中包括两名女性。主要研究人员正在积极招募来自城市高中和少数族裔的新生参与这个项目。参与该项目的德州农工大学学生被鼓励成为志愿者，并参与Brazos Valley自然历史博物馆建立的外展活动。研究生打算在专业会议和弗吉尼亚科学教师协会的会议上展示他们的发现，并通过弗吉尼亚科学标准研究所传播结果。一旦有了重要的结果，项目人员将领导弗吉尼亚实地会议，这是一个每年一次的实地考察，迎合了广泛的参与者。此外，加拿大合作者和南非硕士候选人的参与为该项目增加了国际成分。来自该项目的科学成果将通过专业地球科学会议的报告和同行评议的科学文献传播。

The Iapetus Ocean is a first-order early Paleozoic oceanic tract that separated eastern North America from peri-Gondwanan crustal blocks. Its closure, which juxtaposed North America with these Gond¬wan¬an elements in the Appalachians, imposed new circulation regimes upon the global hydrosphere and atmosphere and it was a major step toward the eventual amal¬gamation of the supercontinent of Pangea. Despite the importance of Iapetus in the global evolution of the Paleozoic, little is known about the timing and nature of its closure, mainly because the original interface between North American and Gondwanan elements, the main Iapetan suture, is unrecognized in the U.S. Appalachians. On the basis of regional geological relationships and scant isotopic data, it is hypothesized that the Chopawamsic fault in central Virginia represents the main Iapetan suture in the US Appalachians. This project is testing this hypothesis by inte¬grating the results of Nd- and Pb- isotopic studies of magmatic rocks on either side of the fault; by a U-Pb zircon geochron¬ologic study of detrital zircon populations from either side of, and in strata lying above, the fault; by using high resolution U-Pb geochronology on selected magmatic units, and by a kinematic and geochronologic analysis of the fault. This study is a collaborative effort between researchers at North Carolina State University and Texas A&M University.Appalachian geology governs resources (mineral, water) for, and influences the wellbeing (seismic hazards) of, the densest human population in North America; logically, a basic understanding of the bedrock geology is essential to further development and sustainability in the region. Results of this study will also take multiple paths into the broader domains of education and outreach. The project partially supports eight students, including two females. The principal investigators are actively recruiting incoming freshman from urban high schools and from minority groups to work on this project. Texas A&M students involved in the project are encouraged to volunteer and participate in established outreach functions with the Brazos Valley Museum of Natural History. Graduate students intend to present their findings at both professional meetings and at meetings of the Virginia Association of Science Teachers, and disseminate results through the Virginia Science Standards Institute. Once significant results are available, project personnel will lead the Virginia Field Conference, an annual field trip that caters to a broad array of participants. In addition, the involvement of Canadian collaborators and a South African MS candidate adds an international component to the project. Scientific results that derive from the project will be disseminated via presentations at professional geoscience meetings and the peer-reviewed scientific literature.