Cosmic impact versus terrestrial origin of the Azuara structure (Spain): A review

Abstract

The Azuara structure is the largest one proposed so far in Spain as possibly related to a cosmic impact event. A review of the evidence set forward in favor of and against its cosmic origin indicates that the discussion is not yet finished. Some megascopic features (inverted stratigraphy, megabreccia, negative gravity anomalies) and shock-metamorphic effects (planar deformational features) have been described in relation with the structure, although their real significance has been questioned and is still being debated. Comparison with other similar-sized verified impacts suggests that unequivocal impactogenic features are yet to be found before the Azuara structure can be related to a cosmic impact. Until then, the Azuara structure should be considered as an unverified impact structure, and should not be included in global comprehensive maps of terrestrial impact structures.