Active tectonics,fault patterns,and stress field of Deception Island: A response to oblique convergence between the Pacific and Antarctic plates |
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| Institution: | 1. Department of Earth Sciences, University of Bristol, Wills Memorial Building, Bristol, BS81RJ, UK;2. Centre for Geographical Studies, Institute of Geography and Spatial Planning, University of Lisbon, Lisbon, Portugal;3. Dept. Géographie & Centre d’études nordiques, Université Laval, Quebec, Canada;4. Institute of Earth Sciences Jaume Almera, ICTJA-CSIC, Lluis Solé i Sabaris s/n, 08028 Barcelona, Spain;5. Centro de Investigación, Seguimiento y Evaluación, Parque Nacional de la Sierra de Guadarrama, Rascafría (Madrid), Spain;6. Centre for Ecological Research and Forestry Applications (CREAF-CSIC), Cerdanyola del Vallès, Catalonia, Spain;7. Centre for Hydrographical Studies (CEDEX), Madrid, Spain;1. Institute of Earth Sciences Jaume Almera, ICTJA-CSIC, Group of Volcanology, SIMGEO (UB-CSIC), Lluís Solé i Sabarís s/n, 08028 Barcelona, Spain;2. Centro de Geociencias, Universidad Nacional Autónoma de México, Campus Juriquilla, Querétaro, Qro. 76230, Mexico;1. Laboratório de PaleoEcologia Tropica, Departamento de Geologia Marinha, Instituto de Geociências, Universidade Federal Fluminense, Avenida Litorânea s/n, 24210-340 Niterói, RJ, Brasil;2. LAGEMAR, Instituto de Geociências, Universidade Federal Fluminense, Avenida Litorânea s/n, 24210-340 Niterói, RJ, Brasil;3. Laboratório de Análise Micropaleontológica - MicroCentro, Departamento de Geologia, Universidade Federal do Rio de Janeiro, Ilha do Fundão, 21949-900 Rio de Janeiro, RJ, Brasil;4. Instituto Oswaldo Cruz, Fundação Oswaldo Cruz, Av. Brasil 4365, 21040-900 Rio de Janeiro, RJ, Brasil;1. Department of Geology, Portland State University, Portland, OR 97201, USA;2. Institute for Geophysics, University of Texas, Austin, TX 78758, USA;3. Dept. of Civil & Environmental Engineering, Pennsylvania State University, University Park, PA 16802, USA;4. Department of Biology, University of New Mexico, Albuquerque, NM 87131, USA |
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| Abstract: | Palaeostress results derived from brittle mesoscopic structures on Deception Island (Bransfield Trough, Western Antarctica) show a recent stress field characterized by an extensional regime, with local compressional stress states. The maximum horizontal stress (σy) shows NW–SE and NNE–SSW to NE–SW orientations and horizontal extension (σ3) in NE–SW and WNW–ESE to NW–SE directions. Alignments of mesofractures show a maximum of NNE–SSW orientation and several relative maxima striking N030-050E, N060-080E, N110-120E, and N160-170E. Subaerial and submarine macrofaults of Deception Island show six main systems controlling the morphology of the island: N–S, NNE–SSW, NE–SW, ENE–WSW to E–W, WNW–ESE, and NNW–SSE. Geochemical patterns related to submarine hydrothermally influenced fault and fissure pathways also share the same trends. The orientation of these fault systems is compared to Riedel shear fractures. Following this model, we propose two evolutionary stages from geometrical relationships between the location and orientation of joints and faults. These stages imply a counter-clockwise rotation of Deception Island, which may be linked to a regional left-lateral strike-slip. In addition, the simple shear zone could be a response to oblique convergence between the Antarctic and Pacific plates. This stress direction is consistent with the present-day movements between the Antarctic, Scotia, and Pacific plates. Nevertheless, present basalt-andesitic volcanism and deep earthquake focal mechanisms may indicate rollback of the former Phoenix subducted slab, which is presently amalgamated with the Pacific plate. We postulate that both mechanisms could occur simultaneously. |
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