The inverted margin of the French Alps and foreland basin inversion

Abstract

The whole of the Western Alpine realm can be considered to result from the inversion of the European margin of Ligurian Tethys as a consequence of the collision between Apulia and Europe. The margin was developed due to Tethyan rifting during the Liassic and Middle Jurassic and regional thermal subsidence as the Ligurian ocean was spreading in the Late Jurassic and Early Cretaceous. Coevally, the margin underwent additional stretching in response to North Atlantic rifting. Inversion was initiated by Late Cretaceous times when the Ligurian oceanic crust began to be subducted, with localized obduction, beneath the previously passive margin. The most recent inversion of the Western Alps occurred in the external Molasse basin of Manosque-Digne-Valensole during the Late Miocene and Pliocene. Regions of mild inversion allow useful comparisons to be made with more strongly inverted basins. The geometric characteristics of the inverted basins depend on the lithology, geometry of the extensional structures, orientation of extensional faults with respect to the compressive Alpine stresses and the amount of compression. Comparisons of the external and internal zones suggest that the ductilely deformed thrust sheets may have originated from inverted half-grabens.

Mechanisms of margin inversion in the external Western Alps: Implications for crustal rheology

“…During the Liassic to Dogger times, the crust was stretched and steep normal faults dissected the upper crust into several tilted blocks separated by halfgrabens with thick depocenters of marly sediments (Barféty et al, 1979;Lemoine et al, 1981;Lemoine et al, 1986;Tricart and Lemoine, 1986;de Graciansky et al, 1989). Since the end of Dogger times the oceanic basin opened and a thick post-rift sedimentary cover was deposited.…”

Cenozoic contractional reactivation of Mesozoic extensional structures in the Eastern Cordillera of Colombia

“…In fact, in many regions the recognition of reactivated extensional structures during shortening helped to reveal the salient structural features of mountain belts. Impressive examples include the western Alps [Gillcrist et al, 1987;Graciansky et al, 1989;Coward et al, 1991], the Santa Barbara structural province of NW Argentina [Grier et al, 1991;Mon and Salfity, 1995;Kley and Monaldi, 2002] or the Atlas Mountains of Morocco [Teixell et al, 2003]. For a better understanding of the spatial and temporal evolution of orogens it is therefore important to consider their structural framework in the context of preexisting anisotropies and zones of weakness in the crust.…”

Inversion of a transfer system into lateral ramps: An example from the South-Central Pyrenees (Spain)

“…Subsurface examples have been described by Badley et al (1989), Letouzey (1990) and Ziegler (1983), and surface examples by Butler (1989), Graciansky et al (1989) and Doglioni (1992). Inversion processes involving Mesozoic (Berastegui et al 1990;Boillot and Capdevila 1977) and even Paleogene sedimentary rocks (Hayward and Graham 1989;Martínez et al 1989;Pujadas et al 1989) have been recognized in the Pyrenees.…”