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Long-lasting diapir growth history in the Basque- Cantabrian basin (Northern Spain): a review
  • Yohann Poprawski,
  • Christophe Basile
Yohann Poprawski
Independant geologist

Corresponding Author:[email protected]

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Christophe Basile
ISTerre, 1381 Rue de la Piscine, 38610 Gières, FRANCE
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The Basque-Cantabrian basin is located in northern Spain in the westernmost part of the Pyrenees. It is a Mesozoic rift, inverted during the Tertiary. In this basin, a subsiding deep-water depocenter, called the Basque Trough formed during the Early Cretaceous, in response to the opening of the Bay of Biscay. In the Basque-Cantabrian basin, the Triassic salt-bearing red clays are exposed in several diapirs that display discordant contacts with the Mesozoic and the Tertiary successions, suggesting a long-lasting halokinetic growth at regional scale. The synthesis of previously published works, together with the analysis of the geological maps from the Spanish geological survey (IGME) as well as the building of new structural cross-sections, allows reviewing the history of halokinesis in the basin. At least four distinct areas may be defined according to the paleogeographical locations of the diapirs: the northern and southern margins of the Basque Trough, and the southern and eastern areas of the Basque-Cantabrian basin. In the northern margin of the Basque Trough, the Bakio and Gernika diapirs mainly recorded an Aptian-Albian growth history, although older and younger growth cannot be ruled out. These diapirs were growing in relatively deep-water environments and created some paleo-highs where isolated carbonate platforms developped. In the southern margin of the Basque Trough, the Villasana de Mena, Orduña, Murguía diapirs recorded an Early Cretaceous to Late Turonian growth evolution. These diapirs were growing in relatively shallow-water environments at the shelf of the southern margin. In the southern area of the Basque-Cantabrian basin, the Salinas de Rosío and Salinas de Añana diapirs recorded a Cretaceous salt growth in a shallow-marine to continental environment and the Tertiary reactivation during the inversion of the basin. The Salinas de Rosío diapir shows a salt glacier overlying the adjacent Tertiary Villarcayo Syncline that displays a mini-basin shape with a strong thinning of the Tertiary succession toward its margins. In the eastern area of the Basque-Cantabrian basin, five diapirs (Estella, Alloz, Salinas de Oro, Ollo and Anoz) are aligned along the Pamplona fault, that represent a Cretaceous transverse fault bounding the Basque Trough to the east. The Tertiary succession covers the older units masking the possible Cretaceous salt growth evolution. However, strong thinning of the Tertiary succession toward these diapirs together with the lateral facies changes highlights the Tertiary reactivation of these structures during the basin inversion. The compilation of all these data allows creating a geological chart that depicts the evolution of the salt structures through time and in the different areas of the Basque-Cantabrian basin.