Actividad Tectónica Sinsedimentaria en el Jurásico del Sur de la Cuenca Neuquina.

FREIJE, H.; AZÚA, G.; GONZÁLEZ, R.; PONCE, J.J.; ZAVALA, C.

Mar del Plata

Congreso; V Congreso de Exploración y Desarrollo de Hidrocarburos; 2002

Jurassic synsedimentary tectonics in the southern part of the Neuquén Basin. Detailed field studies in the Quebrada del Sapo – Picún Leufú area allowed the recognition of nine unconformity-bounded stratigraphic units, which are partially equivalent to Los Molles, Lajas, Challacó, Lotena, Tordillo, Vaca Muerta and Quintuco formations. These units ranging in age from Early Bajocian to Late Tithonian, and often display folding, truncation and onlap relationships at their boundaries. These characteristics strongly suggest a tectonic control in their origin. The number and significance of different tectonic episodes is consistent with a complex deformational history mainly acting along two different structural axes, which were roughly oriented east-west and  north-south. The east-west axis provides the best resolution due to the number of units involved. According to the stratigraphy, this last structure shows along time evidences of both compression and extension, that could be related to the shallow expression of  tectonic movements of a deep high-angle (basement-involved?) fault system. Main compressive activity seems to occurred during the Bathonian, which is substantially older that previously considered for the area (Intramalm unconformity). Broadly speaking, compressive activity appears to be occurred during the deposition of overall regressive units (Lajas, Challacó and Tordillo formations), while major transgressions (Lotena and Vaca Muerta formations) apparently coincided with extensional events. These observations provide new insights to discuss the eustasy vs. tectonics imprints in the stratigraphic record of the Neuquén basin. On the other hand, if the main buried fault responses to regional stresses, then the recorded activity could be used to analyze the progressive geodynamic evolution of the basin during the studied interval.