Early foreland deformation of the Fuegian Andes (Argentina): Constraints from the strain analysis of Upper Cretaceous-Danian sedimentary rocks |
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| Institution: | 1. Centro Austral de Investigaciones Científicas (CADIC-CONICET), Bernardo A. Houssay 200, 9410 Ushuaia, Tierra del Fuego, Argentina;2. Instituto Geológico del Sur (INGEOSUR-CONICET), Departamento de Geología, Universidad Nacional del Sur, San Juan 670, 8000 Bahía Blanca, Buenos Aires, Argentina;1. NEG-LABISE, Departamento de Geologia, UFPE, Recife, PE, 50740-550, Brazil;2. INSUGEO, Universidad de Tucuman, Tucuman, 4000, Argentina;3. Departamento de Geología, Centro de Excelencia en Geotermia de los Andes, Universidad de Chile, Santiago, Chile;4. Departamento de Geologia e Geofísica Aplicada, Instituto de Geociências, UFBA, Salvador, BA, 40170-290, Brazil;5. Instituto de Agrobiología y Recursos Naturales CSIC, 37071, Salamanca, Spain;1. Universidad Nacional de la Patagonia San Juan Bosco, Dpto. de Geología, Argentina;2. Laboratorio de Geodinámica Interna, IDEAN, Universidad de Buenos Aires, Argentina;3. CONICET, Argentina;4. Instituto Geofísico Sismológico Ing. F.S. Volponi (IGSV), San Juan, Argentina;5. CAPSA-Capex, Argentina;6. YPF S.A, Argentina;1. Instituto Geofísico Sismológico Volponi, FCEFN, Universidad Nacional de San Juan, CONICET, Ruta 12 Marquesado (Jardín de Los Poetas), Rivadavia, San Juan, Argentina;2. IDEAN-CONICET, Universidad de Buenos Aires, Argentina |
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| Abstract: | This contribution addresses new structural data from Upper Cretaceous-Danian sedimentary rocks of the Fuegian Andes orogenic front in Argentina. The structures studied, called D′, were formed during the early foreland deformation of the orogen, in the Late Cretaceous-Danian, in times when South America and Antarctica were still connected. The strain analysis of these structures indicates that deformation occurred at upper-crustal depths, and was characterized by flexural folding accompanied by formation of pressure-solution tectonic foliations in zones of higher strain. Deformation intensities increase toward the hinterland and with depth. The history of deformation involved progression from layer-parallel shortening to folding above a detachment, and further formation of a forward-propagating thrust wedge. Layer-parallel shortening and incipient folding recorded in Maastrichtian-Danian rocks indicate the leading edge of D′ deformation. Non-coaxial finite strain orientations were involved during formation of D′ structures along the Fuegian Andes front. These finite strain orientations cannot be explained with the SW-NE regional contraction usually assumed to have driven Andean deformation in this region; alternatively, we consider that N-S contraction combined with buttressing against the cratonic foreland comprise a more suitable interpretation for D′ and younger deformation. |
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