On the origin of NE-SW fracturing in the Aínsa Basin-External Sierras (Central Pyrenees)
DOI:
https://doi.org/10.55407/geogaceta108702Keywords:
pyrenean Chain, structural analysis, monocline, conjugate faults, salt tectonicsAbstract
A fracture system found in the Aínsa basin-External Sierras (Central Pyrenees) area is here analysed. This study performs a structural analysis of fracture geometry and orientation along three stratigraphic units: The calcareous Guara Fm., the Sobrarbe Fm., and the Escanilla Fm. The general structure is characterised by a kilometer-scale monocline underlain by the South Pyrenean main thrust. The mapping and the analysis of fractures data allows to define three main sets: the first set presents a NE-SW direction, the second one a NW-SE direction and the last one a N-S direction. Kinematic indicators of the N-S set indicate a clear dextral movement, and cartographic features show that the NE-SW set is constituted by steeply-dipping normal faults with downthrown blocks to the SE. The main fracture sets (NE-SW and N-S) can be interpreted as an initially conjugate strike-slip system where the σ1 axis is located around 020. Subsequently, these faults could be reactivated as steeply-dipping normal faults due to salt tectonics related to extrusion of the Upper Triassic towards the Naval diapir.
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Copyright (c) 2025 Lorena Bentué Lalueza, Teresa Román-Berdiel, Antonio Casas Sainz
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