INSTITUTO ARGENTINO DE NIVOLOGIA, GLACIOLOGIA Y CIENCIAS AMBIENTALES
Unidad Ejecutora - UE
Geodynamic context for the deposition of coarse-grained deep-water axial channel systemas in the Patagonian Andes
GHIGLIONE, M.C.; LIKERMAN, J.; BARBERON, V.; GIAMBIAGI, L.,; AGUIRRE-URRETA B.; SUAREZ, F.
WILEY-BLACKWELL PUBLISHING, INC
Lugar: Londres; Año: 2014 vol. 26 p. 726 - 726
Distribution of Mesozoic rifts is a first-order control determining along-strike variations in the structural style of the Andes, associated with a grand scale geotectonic segmentation. We present a tectonic model for the structural segmentation of the Southern Patagonian Andes, integrating the fold thrust belt between Lago Viedma and Seno Última Esperanza (49º 30´ - 51º 30´ SL) through updated geological mapping and balanced cross-sections. This area is part of the northern Austral (Magallanes) basin where Mid to Late Jurassic rifting tectonosequences are overlaid by a thick tabular sedimentary section of Cretaceous to Cenozoic sag and foreland basin deposits. The structural geometry and the transition between domains of the fold-thrust belt is illustrated by four ~E-W serial balanced cross-sections. Master faults and structural boundaries where mapped and correlated throughout the cross-sections showing strong along axis variations in width and lateral position of the structural domains. Variations take place in three discrete ~E-W transition zones: the two northern zones coincide with Viedma and Argentino lakes, while the southern one runs at ~50º 55` LS, just north of Sarmiento lake. Our observations where extrapolated to define a regional pattern of transverse segmentation and lateral variation in structural style between 48º and 53º SL. All in all, we show that the structural trend is characterized by overall thick-skinned deformation involving Paleozoic basement north of San Martín lake (Makena transition zone), thin-skinned deformation between San Martín and Argentino lakes, and inversion tectonic southward from there. Two competing factors are recognized as the responsible for changes in the structural style from thin-skinned or thick-skinned deformation: (i) variations in thickness of sag plus foreland sequences and (ii) differential development of extensional master faults. We conclude that the distribution of extensional depocenters from the Jurassic rifting phase controlled the two mentioned factors, that on time shaped the north-south structural contrasts and along axis variations of the structural domains. In our presented model, east-west oriented transition zones are located, quantified, and, based upon previous proposals, interpreted as the superficial expression of accommodation zones separating Jurassic synrift sub-basins.