--> ABSTRACT: Crustal Balanced Cross Sections and Post-Jurassic Evolution of the Pyrenees, by P. Desegaulx, F. Roure, and A. Villien; #91032 (2010)
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Crustal Previous HitBalancedTop Cross Sections and Post-Jurassic Evolution of the Pyrenees

P. Desegaulx, F. Roure, A. Villien

The ECORS deep seismic profile shows constraints on the crustal geometry of the Pyrenees, from the Ebro basin to the Aquitaine including the axial zone. Both forelands are flexed toward the axis of the belt, whereas nappes are north verging in the north and south verging in the south, giving a superficial V-shape to the Pyrenees.

At depth the Pyrenees are disymmetric. The lower Iberian crust plunges slightly northward underneath a wedge of the European lithosphere. This deforms the ancient plate boundary, with the north Pyrenean fault being cut by north-verging thrust planes.

Different models have been tested to restore previous geometries of the Pyrenees. They imply about 100 km of shortening since the Late Cretaceous. Two initial configurations are discussed to account for the left slip of Iberia during the opening of the Bay of Biscaye, Albian pull-apart basins, and Pyrenean metamorphism. The first involves crustal denudation along a large-scale detachment fault; the popular alternative combines strike-slip faulting and thinning of the European crust along a steep transform plate boundary.

Besides Albian and modern configurations, intermediate geometries reflect the kinematic evolution of the Pyrenees. Crustal shortening started along the southern European margin in the Late Cretaceous, inducing inversion of the Albian physiography and deposition of synorogenic flysches in the northern foredeep. During the Eocene, both the Iberian and European margins were shortened and flexed, giving rise to the fan shape of the Pyrenees. In late Oligocene and early Miocene time, only the southern front was tectonically active, responding to a limited subduction of the Iberian continental lithosphere. By Neogene times, uplift affected the axial zone, reflecting isostatic equilibrium of its crustal roots.

AAPG Search and Discovery Article #91032©1988 Mediterranean Basins Conference and Exhibition, Nice, France, 25-28 September 1988.