The Triangle Zone of the Argentine Precordillera: Insights From the Integration of Geological and Geophysical Data

Abstract

This paper reports the results of the combination of multiple geological and geophysical exploration techniques in both pre-drill and post-drill exploration stages. Detailed geological mapping and regional gravimetric and magnetoteluric surveys have been integrated with existing poor quality seismic data in order to search for buried traps at the northern triangle zone of the Argentine Precordillera. The model was tested by a 10000 feet study well whose lithological and structural data helped to calibrate the pre-drill interpretation. Outcropping foreland basin deposits delineates a NNE- oriented upright fold located at the downthrown block of a major east-verging thrust sheet. The fold has a fault near its crest and is dissected by a NE-SW trending left-lateral strike-slip fault. Near the edge of the triangle zone, high dipping beds of conglomerates are related to a series of NNW- striking backthrusts. The Bouguer anomaly map shows a clear tectonic boundary between basement-involved structures to the east and a lower density sedimentary fill of variable thickness to the west. Roughly E-W and N-S oriented magnetoteluric sections allowed the recognition of lateral variations on the resistivity response of the sedimentary cover that can be related to reverse fault juxtaposition. A deep high resistivity zone delineates a positive feature with a NW-SE strike that could be related to a west-verging fault-related fold. The analysis of the well path deviation, drilled lithology and beds and fractures orientation from image logs allowed the recognition of structural domains, fault zones and stratigraphic repetitions. Those features were successfully correlated with the outcropping geology resulting in a better understanding of the subsurface structural geometry. Post-drill data acquisition and reprocessing along a key magnetoteluric section improved the resolution of the model and recognized lateral variations that can be related to opposing vergence structures. The integration of surface and subsurface data helped to reduce the model uncertainty and provided methodological insights for future exploration at the triangle zone of the Argentine Precordillera and other fold and thrust belts.

AAPG Datapages/Search and Discovery Article #90217 © 2015 International Conference & Exhibition, Melbourne, Australia, September 13-16, 2015