Abstract

ARIZA, Juan et al. Interpretación estructural de una sección geológica en las nacientes del río San Juan, a partir de datos geológicos y validación geofísica. Rev. Asoc. Geol. Argent. [online]. 2015, vol.72, n.4, pp.495-505. ISSN 0004-4822.

We present a subsurface structural reconstruction from a NE-SW cross section at the San Juan river headwaters, in the Western Precordillera. The stratigraphy of study area is mainly represented by marine rocks of lower-middle Paleozoic age which are uncomformably covered by Neopaleozoic continental and marine rocks. The structure is characterized by thrust and fold systems of different scales. The thrusts have been separated into two groups: Group I corresponds to NW-SE thrusts with southwestward vergence, while Group II is represented by N-S thrusts with eastward vergence. The superficial relationship between the structures from both groups allows us to postulate that the Group I thrusts are older than Group II thrusts. The similar folds have southwestward vergence and they are frequently related to development of axial plane cleavage and a conspicuous low grade metamorphic event. The geometry of thrusts and folds on surface has allowed us to reconstruct their distribution in depth. Residual magnetic anomaly and analytical signal maps show the correspondence between the superficial structural frame and the magnetic properties in the study area. The solutions provided by the Werner method and its different structural indexes (dykes and contacts) have allow us to adjust and constrain the structural model up to a depth of 3500 m coincident with the subsurface region of maximum magnetic contrast.

Keywords : Magnetic map; Analytic signal; Andean structure; Pre-andean structure.

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