Facies distribution along salt walls: The Upper Cretaceous mixed siliciclastic-carbonate deposits of the Cotiella minibasins (Southern Pyrenees, Spain)

To assess the influence of growing salt structures on facies distribution, stratal pattern, and thickness trends, this paper provides the tectonostratigraphic framework of the outstandingly exposed Cotiella minibasins (South -Central Pyrenees, Spain). Based on detailed analysis of field cross-sections, our results showcase the syn-halokinetic upper Coniacian-lower Santonian Cotiella minibasins infill (1.5-3 km thick) records four shallow -marine depositional sequences, made of mixed siliciclastic-carbonate stratigraphic sequences. This infill is sub-divided in three tectonostratigraphic units, identified by using large and small-scale halokinetic structures (i.e. wedges, megaflaps) and variations in facies associations, thicknesses, stratal patterns from the salt wall flanks to the central part of the minibasins. The first unit records the onset of salt movement with overlying laterally continuous sheet-like sedimentary layers and progressive facies transitions over distances of kms. The influence of halokinesis on sedimentation patterns was minor, and only impacted thickness trends and depocenters localization. The second unit records salt evacuation at the surface with the presence of salt-wall derived detritus, the rapid downbuilding and a increase of sand-rich facies proportions. The stratal pattern is characterized by sheet like layers, laterally discontinuous over distances of 300-600 m downdip to the salt wall. Topographically elevated salt walls likely amplified tidal currents, implying sand-rich facies accumulation along the salt wall margin. The halokinesis influence on sedimentation, thickness trends and depocenter localization was signifi-cant. The third unit records the end of the salt evacuation stage, marking a brutal decrease of sand-rich facies, likely controlled by regional controls such as eustacy and tectonics. The influence of halokinesis on sedimen-tation patterns, thickness trends, large-scale geometries and depocenter localization was significant. Our work indicates that distinguishing these large-scale tectonostratigraphic units and their characteristics is of prime importance to understand the archetypal facies distribution, thickness and stratal patterns along salt structures margins.

Automated summary

This paper provides a tectonostratigraphic framework of the Cotiella minibasins in the Pyrenees, Spain, to assess the influence of salt structures on facies distribution, stratal pattern, and thickness trends. The results show that the influence of halokinesis on sedimentation patterns, thickness trends, and depocenter localization is significant.