Kinematic analysis of a transtensional fault system: the Atuel depocentre of the Neuquén basin, Central Andes, Argentina.

BECHIS, F., GIAMBIAGI, L., GARCÍA, V., LANÉS, S., CRISTALLINI, E..Y TUNIK, M.

JOURNAL OF STRUCTURAL GEOLOGY

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2010 vol. 32 p. 886 - 899

0191-8141

The Atuel depocentre of the Neuquén basin was originated as an Upper Triassic to Lower Jurassic rift system, later inverted during compressive deformation in the present southern Central Andes. In order to study the extensional architecture and the kinematic evolution of this depocentre, we collected a great amount of field and sub-surface data, consisting of slip data from outcrop-scale normal faults, thickness and facies distribution within the synrift deposits, and structural data from angular and progressive unconformities. The Atuel depocentre has a NNW trend, showing a bimodal distribution of NNW and WNW major faults (first and second order faults). On the other hand, from kinematic indicators measured on outcrop-scale faults (third and fourth order faults), we found a mean NE internal extension direction, which is oblique to the general trend of the sub-basin. Taking into account these particular characteristics, we interpreted the Atuel depocentre as an oblique rift system. We evaluated two mechanisms in order to explain the development of this transtensional system: 1) reactivation of upper-crustal NNW-oriented weak discrete fabrics, and 2) oblique stretching of a previous wide NNW-oriented lithospheric weakness zone.