Plio-Quaternary extension in the Venezuelan Andes: Mapping from SAR JERS imagery

Copyright © 2005 Elsevier B.V. All rights reserved.Damien Dhont, Guillaume Backé and Yves Hervouëthttp://www.elsevier.com/wps/find/journaldescription.cws_home/503362/description#descriptio

Spatial and temporal relationships between compression, strike-slip and extension in the Central Venezuelan Andes: Clues for Plio-Quaternary tectonic escape

Copyright © 2006 Elsevier B.V. All rights reserved.Guillaume Backé, Damien Dhont and Yves Hervouëthttp://www.elsevier.com/wps/find/journaldescription.cws_home/503362/description#descriptio

Neogene tectonostratigraphic history of the southern Neuquén basin (39°-40°30′S, Argentina): Implications for foreland basin evolution

International audienceAlthough the Neuquén basin in Argentina forms a key transitional domain between the south-central Andes and the Patagonian Andes, its Cenozoic history is poorly documented. We focus on the sedimentologic and tectonic evolution of the southern part of this basin, at 39-40°30′S, based on study of 14 sedimentary sections. We provide evidence that this basin underwent alternating erosion and deposition of reworked volcaniclastic material in continental and fluvial settings during the Neogene. In particular, basement uplift of the Sañico Massif, due to Late Miocene-Pliocene intensification of tectonic activity, led to sediment partitioning in the basin. During this interval, sedimentation was restricted to the internal domain and the Collon Cura basin evolved towards an endorheic intermontane basin. From stratigraphic interpretation, this basin remained isolated 7-11 Myr. Nevertheless, ephemeral gateways seem to have existed, because we observe a thin succession downstream of the Sañico Massif contemporaneous with the Collon Cura basin-fill sequence. Comparisons of stratigraphic, paleoenvironmental and tectonic features of the southern Neuquén basin with other foreland basins of South America allow us to classify it as a broken foreland with the development of an intermontane basin from Late Miocene to Late Pliocene. This implies a thick-skinned structural style for this basin, with reactivation of basement faults responsible for exhumation of the Sañico Massif. Comparison of several broken forelands of South America allows us to propose two categories of intermontane basins according to their structural setting: subsiding or uplifted basins, which has strong implications on their excavation histories

Plio-Quaternary thin-skinned tectonics along the crustal front flexure of the southern Central Andes: A record of the regional stress regime or of local tectonic-driven gravitational processes?

We present here a record of Plio-Pleistocene deformations above the flexural front of the southern Central Andes of Argentina. We combine a seismic profile with structural and geomorphological observations to show that thin-skinned extension located on top of the crustal front flexure is coeval with thin-skinned shortening at the toe of the topographic bulge. The seismic line shows that a flat zone with no internal deformation separates the stretched and shortened domains. Such features are usually interpreted as the result of strike-slip faulting along basement faults, or tangential longitudinal strain folding in the soft sedimentary cover above crustal bending. We propose an alternative linking extension at the apex of the crustal anticline, to basal contraction by the downslope translation of a rigid thin nappe of sediments (30 × 30 km2 in area) above evaporites at a depth of 700-900 m. The size of such a process is unusually large onshore (630-810 km3) but mimics the gravity gliding observed in deltas and passive margins. Since this process disconnects zones with a shallow stress field from deeper crustal levels, it could allow extension above a compressive deformation front and should not be interpreted merely as a record of the crustal stress regime. Large-scale gravity gliding of the cover down the slope of a structural high could also explain some of the extension observed in mountain hinterlands.Peer reviewe