Translation, collision and vertical-axis rotation in the Organyà and Montsec minibasins (South-Central Pyrenees, Spain)
Resumen
This paper presents a sequentially restored cross-section of the Organyà and Montsec minibasins based on geological mapping, new field observations and available borehole data. The main objective was to describe the geometry and evolution of both basins in terms of salt tectonics and minibasin mobility. To this end, a comprehensive palaeomagnetic database has been used to constrain vertical-axis rotations potentially related to minibasin translation and pivoting. The Organyà minibasin constitutes an asymmetric depocentre formed during the Upper Jurassic-Lower Cretaceous by translation above a southerly inclined salt layer. Salt evacuation and minibasin touchdown induced salt accumulation on the northern side of the basin that culminated in the development of the major Santa Fe unconformity during the late Albian—early Cenomanian. Indicative of salt quiescence is the following isopachous Cenomanian to lower Santonian sequence Salt tectonics resumed during the late Santonian—Palaeocene, with the Montsec minibasin downbuilding coinciding with the onset of Pyrenean convergence. Changes of the base-salt topography reflects regional-scale geodynamic processes. The acceleration of crustal thinning in the North Pyrenean zone during the late Albian-early Cenomanian favoured uplift in the Axial Zone, increasing slope and triggering salt mobilization in the Southern Pyrenees. Likewise, the onset of contraction renewed the downslope gliding of the Organyà and Montsec minbasins, and supports the idea that the early stages of basin inversion were governed by gravity tectonics. The kinematic reconstruction suggests that the more that 30° counterclockwise vertical axis rotation records pivoting during the suprasalt translation of the Organyà minibasin rather than solely the Iberian microplate rotation.
Descripción
Highlights The sequential growth of the Organyà and Montsec minibasins have been kinematically reconstructed. The Organyà minibasin records translation, vertical rotation and collision processes similar to offshore minibasins. The Santa Fe angular unconformity was formed by salt accretion after the welding of the minibasin to the basement. The uplift of the Axial Zone provides the potential energy to move the salt-detached system southwards. Vertical-axis rotation from the Organyà mobile minibasin may not represent the exact kinematics of the Iberian Plate in the Cretaceous.
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