IGEBA   23946
INSTITUTO DE GEOCIENCIAS BASICAS, APLICADAS Y AMBIENTALES DE BUENOS AIRES
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Constraints on the tectonic evolution of the Santa Cruz Patagonian Southern Andes from anisotropy of magnetic susceptibility and structural data (46°-48°SL)
Autor/es:
ARAMENDIA, I.; GHIGLIONE, M.; RAMOS, M.; MAFFIONE, M.; RAMOS, V.A.; GEUNA, S. E.; BOIXART, G.
Reunión:
Simposio; Primer Simposio de Tectónica Sudamericana; 2016
Resumen:
The Andean orogeny in the eastern Southern PatagonianCordillera is the result of the Mesozoic and Cenozoic subduction history.Particularly, the area located between the Buenos Aires- Carrera and Cochrane-Posadas Lakes (46°- 48°SL) offers an interesting example of the interactionbetween the development of the Patagonian fold and thrust belt in latestCretaceous and early Tertiary times and the Austral foreland basin. Althoughseveral previous works outline the main events in the tectonic evolution ofthis region of the Andes, the timing of deformation and the mechanism are notyet well constrained. In this study, we infer the nature and orientation of thepaleostrain field at the Southern Patagonian Andes during the Early Cretaceous(Aptian-Albian) and Miocene by using anisotropy of magnetic susceptibility(AMS) data. The AMS data are supported and integrated by field structuralevidences. In order to undertake this work, 7 Lower Cretaceous and 8 UpperMiocene sites within the fold and thrust belt were sampled. The stratigraphicrecord between these two periods is limited and does not meet the conditionsfor an AMS study. Interestingly the minimum principal susceptibility k3 is N-Sdirected for the Aptian-Albian trangresive successions of the Río Mayer and RíoBelgrano Formations. When interpreted in terms of strain, this would imply thatmaximum principal strain (s1), had an orthogonal distribution respect to theE-W Andean vergence, which could be related to the stress partitioning causedby subduction of old ridges identified in recent reconstructions. Some authorshave displayed, in their regional tectonic model, the break-up of the AntarcticPeninsula from the west side of Patagonian margin. The Antarctic Peninsuladetachment along with the Weddell Sea opening could be linked with a N-Sdirected compressional stress suffered by the Patagonian Andes. For theMiocene, synextensional growth strata were recognized in the JeinimeniFormation. The normal faults limit the progressive unconformities wedges,inferring a coeval sedimentation with extensional tectonics. The AMS studycarried out on these strata proves that the pulses of deformation andsedimentation are coeval, and can be linked to a late Miocene regionalextensional event. On the other hand, the growth strata could be representing arapid sedimentation in these transgressive successions related to a structuralcollapse.