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

Virginia Polytechnic Institute And State University, Blacksburg VA

Investigators

Abstract

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.