Research Frontiers in Appalachian Geology: A Pre-EARTHSCOPE (USArray) Workshop Proposal

地球望远镜是迄今为止最大的地球科学计划，旨在为我们理解北美大陆的4维演化做出新的和根本的贡献。这一计划的美国阵列组件“将极大地改进大陆岩石圈和更深地幔的地震成像，并将这些图像整合到大陆结构、演化和动力学的悬而未决的问题中”(www.Earthscope e.org)。为了实现这一愿景，地球科学研究人员有必要开始批判性地评估我们目前关于大陆形成的4-D演化记录的知识状况，并提出将对EarthScope提出智力挑战的新问题。美国大陆内的阿巴拉契亚造山带为探索有关大陆演化的一些关键问题提供了地质模板。例如：地体如何共生？吸积地体及其大陆基础设施的三维结构是什么？识别深度侵蚀的地体及其相关缝合带的三维结构特征，将有助于更严格地解释现代增生过程，并有助于区分美国中部常见的埋藏缝合带。岩石圈结构及其变形历史对东海岸现今被动边缘内火山裂谷边缘的发育有何影响？地震数据能否有效地用于成像埋藏的被动边缘、前陆盆地和推断盆地几何形状？关于地体增生机制或逆冲构造的新知识能否与是否存在长寿的古生代沉积中心有关？什么岩石圈结构与阿巴拉契亚山脉的新构造活动有关？该地区发生了许多破坏性的板中地震，岩石圈的详细成像有可能回答关于板中地震的基本问题。高分辨率地震数据能否成为区分中大陆1500 Ma花岗岩-流纹岩省和1000 Ma格伦维尔省的最关键的判别式，该省被认为是阿巴拉契亚古生代的基础？它可能提供了解释阿巴拉契亚造山带许多火成岩/火山岩起源的缺失环节。整个大陆的变形的空间和时间尺度是什么？阿巴拉契亚造山带在其历史的大部分时间里一直处于板块边界，其变形历史/机制的记录可以被识别到北美内部。在整个大陆发展这种地质关系是EarthScope的愿景。研讨会将为所有地球科学家提供一个公开论坛，在EarthScope计划内合作制定新的研究机会，特别是涉及阿巴拉契亚山脉提供的自然实验室的研究机会。讲习班的另一个重要目标是，根据地球范围的更广泛目标，启动开发天气数据库的进程，以确定阿巴拉契亚造山带目前的知识状况。将邀请数据库科学家协助了解利用信息技术分析多学科数据的研究益处。讲习班将进行广泛宣传，并向所有人开放，但计划参加人数限制在50人左右，包括研究生和机构代表。这将能够及时和明确地制定科学主题，从而能够利用EarthScope设施，特别是US阵列组件。研讨会指导委员会包括A.K.Sinha(弗吉尼亚理工大学首席调查员)、J.F.Read(弗吉尼亚理工大学)、Art Goldstein(高露洁大学)和Larry Brown(康奈尔大学)，并将监督研讨会议程的发展。他们还将编写最后的研讨会报告，以便在国家地球科学学会杂志上发表，并提交给国家科学基金会。研讨会的形式将包括分组讨论和全体会议。全体会议将提出当前和大胆的新想法，随后将举行一轮突破性会议。分组会议的报告将产生一套共识建议，以推进阿巴拉契亚地区的研究机会。这些建议将构成研讨会的最后报告。

EarthScope is the largest earth science initiative to date, designed to make new and fundamental contributions to our understanding of the 4-D evolution of continental North America. The U.S.Array component of this initiative "will dramatically improve the seismic imaging of the continental lithosphere and deeper mantle, and integrate these images to unresolved issues of continental structure, evolution and dynamics" (www.Earthscope.org). Towards this vision, it is necessary that earth science researchers begin the process of critically evaluating both the status of our current knowledge regarding the 4-D evolutionary record of continent formation, as well as formulating new questions that will provide the intellectual challenge for EarthScope. The Appalachian orogen within the continental United States provides a geologic template to explore some of the key questions concerning continental evolution .For example:How do terranes accrete? What is the structure in three dimensions of the accreting terrane and its continental infrastructure? Recognizing structural features in 3-D of deeply eroded terranes and associated suture zones will allow for a more rigorous interpretation of both modern accretionary processes, as well as helping discriminate buried suture zones common in the central United States.What is the effect of lithospheric structure and its deformation history on the development of volcanic rifted margins within the present passive margin along the eastern seaboard? Can seismic data be used effectively to image buried passive margins, foreland basins and infer basin geometry? Can new knowledge of terrane accretionary mechanisms or thrust tectonics be related to presence/absence of long lived Paleozoic depocenters? What lithospheric structure is associated with neotectonic activity in the Appalachians? A number of destructive mid-plate earthquakes have occurred in the region, and detailed imaging of the lithosphere holds the potential to answer fundamental questions about mid-plate seismicity.Can high resolution seismic data become the most critical discriminant for distinguishing the 1500Ma granite-rhyolite province of the mid-continent from the 1000 Ma Grenville province assumed to underlie the Paleozoic Appalachians? It may provide the missing link in interpreting the origin of many of the igneous/volcanic rocks of the Appalachian orogen.What are spatial and temporal scales of deformation across the continent? The Appalachian orogen has been at a plate boundary for most of its history, and the record of its deformation history/mechanisms can be recognized into the interior of North America . Developing such geologic relationships across the continent is an EarthScope vision.The workshop will provide an open forum for all earth scientists to collaboratively formulate new research opportunities within the EarthScope program, particularly those involving the natural laboratory provided by the Appalachian Mountains. Another significant objective of the workshop, in keeping with the broader goals of EarthScope, will be to initiate the process of developing synoptic databases that identify the current state of knowledge in the Appalachian orogen. Database scientists will be invited to facilitate the understanding of the research benefits of analyzing multidisciplinary data through use of information technology. The workshop will be widely advertised and open to all, but it is planned that the attendance be limited to approximately 50 individuals, including graduate students and agency representatives. This will enable timely and explicit formulation of science themes that can take advantage of EarthScope facilities, especially the US Array component. The workshop steering committee includes A.K.Sinha (Principal Investigator, Virginia Tech, pitlab@vt.edu), J.F.Read, (Virginia Tech), Art Goldstein (Colgate University) and Larry Brown (Cornell University), and will oversee the development of the workshop agenda. They will also prepare the final workshop report for publication in a national earth science society magazine, as well as for submission to NSF.The workshop format will consist of breakouts coupled with plenary sessions. Plenary sessions will present both current and bold new ideas, and will be followed by a round of breakouts. The reports from the breakout sessions will lead to a consensus set of recommendations for advancing research opportunities in the Appalachian region. These recommendations will constitute the final workshop report.