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Syn-sedimentary Dome-shaped Folding in the Southern Flank of the Sorbas Basin (SE Spain)

Damien Do Couto, Laurent Jolivet, Romain Augier, Charles Gumiaux, Noëmie Lebret, and Nicoloas Folcher

In the Internal zones of the Betic Cordillera, the Sorbas Basin forms part of a mosaic of synorogenic sedimentary basins that initiated during the Serravalian-Tortonian. It has recorded a nearly continuous sedimentation since its initiation and is considered as the reference onshore basin of the Messinian Salinity Crisis. The Sorbas Basin underwent two successive extensional and compressional deformation stages that affected the sedimentation. Synkinematic growth-strata structures of Upper Tortonian age reflect the intense beginning of the compressional tectonic period. Compression suddenly affected the basin at the transition with the Messinian, when the basin was uplifted and intensely eroded. Afterwards, the effects of deformation progressively decreased to reach the present-day overall synclinal geometry of the basin.

In the southern uplifted flank of the Sorbas Basin, more precisely along the Barranco del Infierno, the Messinian Erosional Surface, corresponding to the subaerial erosion of the basin during the Messinian second sea-level fall, has been observed and carefully mapped at the transition between Messinian gypsum and Early Zanclean coastal to deltaic deposits. Structural and geometrical analyses of the post-evaporitic coastal calcareous sandstone (Sorbas Member) reveal several folded structures above the evaporitic formation. Their geometries characterise dome-shaped to antiformal saddle open folds. These structures show two directions of anticlinal fold axis, respectively NE-SW and NW-SE oriented. The cores of folds, where observed, are composed of undeformed gypsum layer exhibiting perfect twinned selenite crystals. The deformation acted during the Zanclean (Pliocene) as syn-kinematic continental deposits are filling the accommodation created between the folds.

We describe and model the 3D geometry of this folds system and discuss the presence of such compressional system above evaporitic layers, raising the question of a component of gravitational sliding in the deformation.

AAPG Search and Discovery Article #90161©2013 AAPG European Regional Conference, Barcelona, Spain, 8-10 April 2013