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1 GROUP of SPECIALISTS on ANTARCTIC NEOTECTONICS (ANTEC) REPORT to XXVI SCAR, JULY, 2000 Activities 1998 – 2000 Plans for 2001

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1 GROUP of SPECIALISTS on ANTARCTIC NEOTECTONICS (ANTEC) REPORT to XXVI SCAR, JULY, 2000 Activities 1998 – 2000 Plans for 2001 GROUP OF SPECIALISTS ON ANTARCTIC NEOTECTONICS (ANTEC) REPORT TO XXVI SCAR, JULY, 2000 Activities 1998 – 2000 Plans for 2001 - 2002 1.0 EXECUTIVE SUMMARY Working from the Terms of Reference for ANTEC developed at XXV SCAR, ANTEC members convened a series of meetings to develop a set of science objectives and implementation strategies to promote research on Antarctic Neotectonics. The broad science questions to be addressed by the ANTEC initiative were defined. The overarching issues identified include: a) differentiating between glacial and tectonic kinematic signals; b) mapping the deep structure of the Antarctic lithosphere and asthenosphere; c) investigation of the seismotectonic features of the Antarctic plate; and d) understanding the nature of coupling between tectonics, climate and erosion. A set of 5 thematic science programs have been identified and coordinators for most of these programs have been specified: · Antarctic Plate-Scale Kinematics · Antarctic Lithospheric Structure and Stress · Active Regional Deformation · Surface Processes · Active Volcanic Processes Science observations required as input were catalogued and short-term and long-term goals for each program have been developed. The objectives and strategies were presented via poster, at community meetings, and posted on the ANTEC web site for comment and input by the Antarctic earth science community. In addition to science program development, major early achievements of ANTEC include: · Convening a symposium on Neotectonic Deformation of the Antarctic Plate at the European Geophysical Society, April, 2000. · Drafting a white paper outlining strategies to strengthen capabilities to conduct seismological research on Antarctic Neotectonics. · Planning optimum geodetic station configurations to measure both rebound and tectonic signals. · Identifying new remote sensing opportunities relevant to Antarctic neotectonics research. · Establishment of a web site and email listserver for communication of ANTEC plans and activities. A forward program for each science component of ANTEC is outlined in this report. The further development of the ANTEC program will be achieved through a science workshop planned for July, 2001, in Siena, Italy. Results of early compilation efforts and results of regional studies on Antarctic neotectonics will be presented at an international science conference planned for 2002 and a major symposium planned for the 9th International Antarctic Earth Science Symposium in 2003. 1 2.0 BACKGROUND The ANTEC Group of Specialists was proposed jointly by the Working Groups on Geology, Solid-Earth Geophysics, and Geodesy & Geographic Information and approved by SCAR at XXV SCAR, Concepcion, Chile, July, 1998. In order to develop an international approach to the study of Antarctic neotectonics and ensure international coordination of new research efforts, ANTEC was charged with a) identification of key sites for geodetic and seismic installations; b) encouraging coordinated deployment of instrument networks (GPS, seismic, gravity); c) promoting optimum protocols for data collection, archiving and distribution to meet the needs of the international Antarctic research community; and d) promotion of scientific research by holding workshops and symposia on the neotectonics and geodynamics of Antarctica. Dr. Terry Wilson, Ohio State University, USA, was appointed as ANTEC Convenor. After discussion between the SCAR Executive and the convenor, 6 additional members were invited to join the ANTEC GoS and membership was finalized in February, 1999. The 1999- 2000 ANTEC membership consisted of: Terry J. Wilson Ohio State University, USA [Neotectonic geology] (Convenor) Robin E. Bell Lamont-Doherty Earth Observatory, USA [Gravity; Crustal structure] Alessandro Capra University of Bologna, Italy [Geodesy] Reinhard Dietrich Technische Universitaet Dresden, Germany [Geodesy, Remote Sensing] Jesus M. Ibañez Instituto Andaluz de Geofisica, Spain [Seismology] Tom James Geological Survey of Canada, Canada [Post-Glacial Rebound] John Manning AUSLIG, Australia [Geodesy, Geographic Information] Andrea Morelli Istituto Nazionale di Geofisica, Italy [Seismology] 3.0 ANTEC SCIENCE PROGRAM 3.1 Definition Of “Neotectonic” To Be Used For Antarctica Recognizing the wide range of time scales used in the diverse research areas relevant to the ANTEC program, including yearly motion rates resolved by GPS, thousand-year time scales of glacial rebound modeling, and million-year time scales of geological processes, it was agreed to establish 5 Ma as the older time limit for the “neotectonic” regime in Antarctica. This will allow an adequate amount of data of geological nature to be compiled, noting that such data is vital to establishing the time scale over which modern regimes may have persisted. 3.2 ANTEC Science Objectives A series of overarching science objectives and questions have been defined by the ANTEC GoS: 3.2.1 Differentiate between glacial and tectonic kinematic signals · Which tectonic features are active? · What rebound patterns are resulting from mass load changes? · Have glacially-induced stresses and strains produced faulting, e.g. as seen in Fennoscandia? Or, did this occur in the Neogene? · What crustal motions are occurring in response to present-day changes in ice mass distribution? 2 3.2.2 Map the deep structure of the Antarctic lithosphere and asthenosphere · How are the mechanical properties of the crust and upper mantle distributed? · What are the thermal properties of the crust and upper mantle? 3.2.3 Investigate the seismotectonic features of the Antarctic plate · What is the actual level of intraplate seismicity? · Do patterns of seismicity / aseismicity relate to ice-mass loads and/or unloading? · What plate kinematics and dynamics are indicated by the seismicity? 3.2.4 Understand the nature of coupling between tectonics, climate and erosion · What is the distribution of active faulting? Actively subsiding rift basins? · What are current and Neogene rates of uplift and denudation? · Documentation of the ages and evolution of landscape patterns. · Is there any relation between uplift and active or post-glacial faulting? · What are the links between active volcanism, postulated mantle plumes, uplift and tectonism? 3.3 ANTEC Science Programs During ad hoc and formal ANTEC meetings, 5 principal science programs were identified. Relevant observations required for each science program and short-term and long-term objectives for each program have been developed. The ANTEC science program is summarized in table format in Appendix 1. The programs are outlined in the sections that follow. In order to solicit broad feedback on this program, Wilson introduced it at a joint meeting of the Working Groups on Geology, Solid Earth Geophysics, Geodesy & Geographic Information, and Glaciology at XXVI SCAR. 3.3.1 Antarctic Plate-Scale Kinematics This program will investigate Antarctic plate motion in the context of global plate motion and plate circuits, possible intraplate motions (e.g., between East and West Antarctica), and continental scale post-glacial rebound patterns. The program will require integration of input from geodesy, post-glacial rebound modeling, ice-sheet mass balance models, relative sea level records and remote sensing. Short- and long-term goals are outlined in Appendix 1. 3.3.2 Antarctic Lithospheric Structure and Stress This program will investigate plate-wide stress patterns, the rheology of the lithosphere as a whole, and crustal rheology and discontinuities. The program will focus on integration of stress models predicted from plate-boundary forces and ice-mass loads, the distribution of seismicity, seismic tomography of the crust and upper mantle, and potential field data on crust and mantle structure. Short- and long-term goals are outlined in Appendix 1. 3.3.3 Active Regional Deformation 3 Three regional intraplate areas are known or suspected to be undergoing active regional deformation: the Scotia Arc/Antarctic Peninsula; the Ross Sea region; and portions of East Antarctica (see Appendix 2). For each of these areas it will be necessary to compile data on neotectonic fault kinematics, crustal structure from remote sensing and potential field data, crustal stress measurements, microseismicity, active displacements from GPS deformation networks, and models of glacial rebound from local ice centers. Short- and long-term goals are outlined in Appendix 1. 3.3.4 Surface Processes The surface processes program will encompass landscape evolution, the relation between glaciation and uplift, and relative sea level records. Data input will be from glacial geology and geomorphology, tectonic geomorphology, uplift chronology and rates, surface exposure dating and remote sensing. Short- and long-term goals are outlined in Appendix 1. 3.3.5 Active Volcanic Processes There will be two main components of this program, consisting of evaluation of mantle thermal anomalies or plumes, and the dynamics of active volcanoes. Input data will include volcanological records of eruption histories, petrological studies, regional seismic tomography and potential field data to map crust and mantle structure, and motion monitoring using remote sensing (altimetry, INSAR), geodesy and seismology. Short- and long-term goals are outlined in Appendix 1. 4.0 1999 – 2000 ACTIVITIES 4.1 Meetings ANTEC members held ad hoc meetings for discussion and planning purposes at a number of international meetings in 1999 and 2000, and held a formal GoS meeting in 2000. Discussions
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