IBIGEO   22622
INSTITUTO DE BIO Y GEOCIENCIAS DEL NOA
Unidad Ejecutora - UE
artículos
Título:
Late Miocene to recent morphotectonic evolution and potential seismic hazard of the northern Lerma valley: Clues from Lomas de Medeiros, Cordillera Oriental, NW Argentina
Autor/es:
GARCÍA, VÍCTOR; HONGN, FERNANDO; CRISTALLINI, ERNESTO
Revista:
TECTONOPHYSICS
Editorial:
ELSEVIER SCIENCE BV
Referencias:
Lugar: Amsterdam; Año: 2013 p. 1238 - 1253
ISSN:
0040-1951
Resumen:
The Lomas de Medeiros are lowrelief hills located at the northern extreme of the Lerma valley,where newstructural,morphological and topographic key data have been collected and integrated with the available stratigraphic and geochronological data in order to elucidate the morphotectonic evolution of the region during the last ~10 Ma. In this area, Pliocene to Lower Pleistocene conglomerates and siltstones (Piquete Formation) are deformed delineating an asymmetrical anticline with eastward vergence, axial plane trending N10°E, and progressive unconformities at the backlimb. Syntectonic sedimentation has been documented as related toN?S trending normal faulting near the fold axis as well. Middle Pleistocene to Holocene thick fluvial conglomerates cover unconformably the Piquete Formation as strath terraces with a few meters of thickness. The higher and oldest terrace has been uplifted more than 160 m respect to the top of Calvimonte Formation conglomerates (~0.33 Ma), its stratigraphic correlate at the undeformed Lerma valley. Detailed topographic profiles of the terraces showevidences of progressive uplifting by folding and the presence of scarps relatedwith reverse faulting. The anticline has been modeled using the fault propagation folding mechanism with a blind ramp dipping 32° to the west and a decollement level located 2.7 km below the surface, at the contact between the Cenozoic cover and the Paleozoic basement. The integration of these observationswith previously published data allowed to establish the morphotectonic evolution of this region during the last 10 Ma. Folded and faultedMiddle Pleistocene to Holocene terraces at Lomas deMedeiros and Upper Pleistocene deposits uplifted at Mojotoro range are strong evidences of the seismogenic potential of the faults related with these morphostructures. Applying relationships with the subsurface rupture length, earthquakes with maximum moment magnitudes (Mw) of 6.5, 7.0 and 7.1 have been estimated for Medeiros, Lesser and Mojotoro faults respectively.