A Triassic syndepositional detachment system, Ischigualasto Provincial Park, northwestern Argentina
The Ischigualasto basin of northwest Argentina contains ~4 km of non-marine strata. In the southeast part of the basin, the Middle Triassic Los Rastros Formation contains a ~1 km ^2 area where rocks exhibit both extensional and contractional deformation features. To the east, both high angle and listric normal faults are the dominant structures. To the west, deformation consists of reverse and thrust faults, in addition to upright and overturned folds. Faults in both areas sole into a sub-horizontal detachment surface, below which rocks are undeformed. Deformed Los Rastros Formation strata are overlain by lightly-deformed/undeformed rocks of the Upper Triassic Ischigualasto Formation. The Agua de la Peña detachment system is interpreted to have formed as a result of gravity spreading/depositional loading of lacustrine delta platform and fluvial deposits above an overpressured shale décollement. Although 2-3 orders of magnitude smaller, the cross-sectional shape and interpreted driving mechanisms of the Agua de la Peña detachment are similar to paired extensional-contractional fault systems formed along continental margins. Based on reconstructed geometry and interpreted rheology, the contractional portion of the detachment can be modeled as a critical-tapered wedge, and provides a small-scale analogue for fold-thrust belts formed in passive-margin settings.
School Location:USA - Ohio
Source Type:Master's Thesis
Keywords:structural geology extension contraction critical tapered wedge
Date of Publication:01/01/2005