Long-lasting diapir growth history in the Basque- Cantabrian basin
(Northern Spain): a review
Abstract
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.