New insights about the Upper Jurassic – Lower Cretaceous sedimentary successions from Asturias (NW Iberian Peninsula)

Abstract

Detailed mapping of the Jurassic to pre-Albian deposits of central and eastern Asturias (NW of the Iberian Peninsula) has enabled several Upper Jurassic and Lower Cretaceous outcrops, previously assigned to other ages, to be identified. Where possible, these outcrops have been correlated with the well-known sequences outcropping on the Asturian coast. A new Jurassic unit, the Miyares Formation, has been defined, which consists of a Lower conglomerate Unit, a Middle Unit composed mainly of oolitic limestones and an Upper Unit comprising bioclastic and marly limestones with a rich fauna of larger foraminifera. The Lower Unit is interpreted as having been deposited in a fan delta, the Middle Unit represents a shallow marine high-energy environment, and the Upper Unit was deposited on a restricted shallow marine platform. The shallow-water foraminiferal assemblage from the Upper Unit is attributed to the Tithonian and the oldest Cretaceous rocks are Barremian; there is therefore a stratigraphic gap recorded in the study area, which might correspond to the latest Jurassic to Early Cretaceous p. p. timespan.