Quaternary deformation around the Palo Negro area,Pampa Norte,Argentina |
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| Authors: | E Brunetto M Iriondo L Zamboni G Gottardi |
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| Institution: | 1. Centro de Investigaciones Científicas (CICyTTP-CONICET) – Materi y España s/n – CP: 3105. Diamante, Entre Ríos, Argentina;2. CONICET, CC. 487, (3100) Paraná, Argentina;1. Centro de Investigaciones Geológicas – CONICET – FCNyM (UNLP), Diagonal 113 N°275, La Plata, Argentina;2. Cementos Avellaneda S.A., Planta San Jacinto, Casilla de Correo 53, Paraje San Jacinto, 7400 Olavarría, Argentina;1. Research School of Earth Sciences, The Australian National University, Canberra, ACT 0200, Australia;2. School of Ocean and Earth Science, University of Southampton, National Oceanography Centre, Southampton SO14 3ZH, UK;1. Departamento de Geología, Universidad Nacional de Río Cuarto, Ruta Nac. Nº 36, Km 601, X5804BYA, Río Cuarto, Córdoba, Argentina;2. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina;1. XR-GEOMAP, R. Durand Av. N 397, Grand Bourg, Salta, Argentina;2. Universidad Nacional de Río Negro, Av. Roca 1242, 8332 General Roca, Río Negro, Argentina;3. University of Saskatchewan, Department of Geological Sciences, 114 Science Place, Saskatoon, Saskatchewan S7N 5E2, Canada;4. Universidad Nacional de La Plata, Paseo del Bosque s/n, 1900 La Plata, Argentina;1. Centro de Investigación y Transferencia de Jujuy (CIT, Jujuy-CONICET), Instituto de Geología y Minería, Universidad Nacional de Jujuy, Av. Bolivia 1661, San Salvador de Jujuy, Argentina;2. Centro de Investigaciones en Ciencias de la Tierra (CICTERRA-CONICET), F.C.E.F. y N., Universidad Nacional de Córdoba, Av. Vélez Sarsfield 1611, X5016GCA Córdoba, Argentina;3. Instituto de Geociencias, Universidad Austral de Chile, Campus Isla Teja, Casilla 567, Valdivia, Chile;4. Aix-Marseille Université, CNRS, IRD, UM 34 CEREGE, Europôle méditerranéen de l''Arbois, BP 80, 13545 Aix-en-Provence Cedex 4, France;5. INCITAP (CONICET) – Universidad Nacional de La Pampa, Avenida Uruguay 151, 6300 Santa Rosa, La Pampa, Argentina;1. Instituto de Geología y Recursos Minerales, Servicio Geológico Minero Argentino, Colectora de Avenida General Paz 5445, edificio 25, piso 2, oficina 201, San Martín, Buenos Aires, 1650, Argentina;2. Instituto de Ciencias de la Tierra y Ambientales de La Pampa, Universidad Nacional de La Pampa-Conicet, Avenida Uruguay 151, 6300, Santa Rosa, La Pampa, Argentina |
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| Abstract: | The Pampa Norte region is a great plain characterized by low slopes and accumulation of hundreds of meters of thick loose sediments. A high morphostructure denominated San Guillermo block stands out in the central plain, the Tostado–Selva scarp forming its western boundary. It is located in an intraplate setting characterized by low tectonic activity. However recent uplift can be inferred by means of terrain analysis and the sedimentology of the Palo Negro Fm. Pond deposits (Palo Negro Fm.) observed in the scarp suggest topographic inversion during the Late Quaternary in the Palo Negro area. The morphology indicates that the deformation was widely distributed, forming a gentle (ca. 5 m amplitude and 13 km wavelength) asymmetric fold. Low sinuosity lineaments located in the base of the scarp, coincident with knick points in the topographic profile, can be interpreted as the projection of tip-lines by high-angle fault-propagation. This geometry is compatible with reverse kinematics on blind faults.A deformation style with reactivation of pre-existing faults is consistent with structural observations. Seismic reflectors suggest the presence of Cretaceous high-angle normal faults, and the orientation of lineaments is similar to the orientation of the graben systems and transverse accommodation zones originated during the opening of the South Atlantic Ocean.One OSL dating of 67.4 ± 5.1 kyr B.P (from Palo Negro Fm. supposed as deposited on a flat plain floor) and a height difference of 9.5 m measured in the Tostado–Selva scarp account for an averaged uplift rate of 0.14 mm/year. |
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