Evidence of a Cenomanian shallow-marine carbonate platform in the northwestern margin of the Bortziriak-Cinco Villas massif, eastern Basque-Cantabrian Basin

Basin margin evolution of rift basins is not always well constrained. In the northeastern margin of the Basque-Cantabrian Basin, a revision of a carbonate succession permits deciphering the transition from synto post-rift phases in the poorly studied northwestern margin of the Bortziriak-Cinco Villas massif. The sedimentological analysis shows three main lithofacies, attributed to a shallow-marine, non-rimmed carbonate platform. On the other hand, biostratigraphic analysis based on the presence of Caprina adversa rudist indicates a Cenomanian age for the succession. Thus, this study illustrates the existence of a Cenomanian shallow-marine carbonate platform unconformably overlying the Palaeozoic massif. This platform development was the result of a generalized transgression during the early post-rift stage.