INVESTIGADORES
MESCUA Jose Francisco
congresos y reuniones científicas
Título:
Tectonostratigraphic evolution of the Atuel depocenter as an oblique rift system during the Late Triassic to Early Jurassic, Neuquén Basin, Argentina
Autor/es:
BECHIS, F.; GIAMBIAGI, L.B.; TUNIK, M.; MESCUA, J.F.
Lugar:
Concepción
Reunión:
Congreso; XV Congreso Geológico Chileno; 2018
Institución organizadora:
Sociedad Geológica de Chile
Resumen:
The Neuquén basin presents an almost continuous record from the Late Triassic until the Paleocene, making itan excellent case study that registers the most relevant tectonic stages of southern South America during theMesozoic. It was initiated in the Late Triassic to Early Jurassic as a continental rift basin in the context of awidespread extensional stage that affected western Gondwana and culminated with the break-up of thesupercontinent.The Atuel depocenter is located in the northern sector of the basin. Synrift and sag units are represented byUpper Triassic to Lower Jurassic siliciclastic marine and continental sedimentary rocks, and it bears the oldestmarine deposits of the basin, of Upper Triassic age. The depocenter infill has been deformed and exhumedduring the Andean orogeny, being presently exposed in the northern sector of the Malargüe fold and thrust belt. Inorder to study the tectono-sedimentary evolution of this depocenter, we integrated a large set of stratigraphic,sedimentologic and structural data into a multidisciplinary approach. We integrated data from facies andthickness distribution of the synrift units, provenance studies on sandstone samples, detrital zircongeochronology data, kinematic data from outcrop scale normal faults, angular and progressive unconformitiesand subsurface information.The structural architecture of the Atuel depocenter is interpreted as related to an oblique rift system, on the basisof the following characteristics: i) a general NNW orientation of the sub-basin, ii) a bimodal distribution of NNWand WNW normal faults, iii) an oblique NE-directed internal extension obtained from kinematic indicatorsmeasured on outcrop-scale faults. It was interpreted as controlled by oblique reactivation of a NNW-orientedlithospheric weakness zone under a regional NNE extension.A paleogeography dominated by active normal faulting controlled marked lateral variations of the depositionalsystems within the depocenter during the synrift stage. Two NNW-trending major normal faults, La Manga andAlumbre, controlled most of the basin subsidence, the distribution of the sedimentary environments and thedrainage patterns. Provenance studies on sandstone samples highlight a major change in the detrital sourcesthat could either be related to the synrift to sag transition, or to a renewed synrift phase by the Toarcian. Thismajor change is also consistent with previous data from detrital zircon analysis.