Latest Jurassic–Early Cretaceous synrift evolution of the Torrelapaja Subbasin (Cameros Basin): implications for Northeast Iberia palaeogeography

Abstract

The reconstruction of the latest Jurassic–Early Cretaceous evolution of the Torrelapaja Subbasin (Cameros Basin, Spain) resulted in the characterization of three synrift sequences (SS-1, SS-2 and SS-3) bounded by major unconformities. Three major NW–SE normal faults combined with smaller scale faults of variable direction (around NE–SW) controlled the sedimentation. The complex geometry of the Torrelapaja Subbasin indicates a main extension direction of NE–SW, and a secondary NW–SE extension. Sedimentation of the Tithonian–middle Berriasian SS-1 occurred in alluvial fan systems, grading upwards to carbonate palustrine-lacustrine environments. A new vertebrate site with large size sauropod bones has been found in the middle part of SS-1. The lower boundary of the uppermost Hauterivian–lower Barremian SS-2 is locally a palaeokarst, with sedimentary infill including three new fossil sites with remains of ornithopod, sauropod and theropod dinosaurs. Sedimentation of SS-2 encompasses distal alluvial terrigenous facies with local palaeosoils and palustrine-lacustrine limestones grading upwards to middle-distal alluvial facies. After a late Barremian–early Albian stratigraphic gap, sedimentation resumed in coastal flat environments represented by the mudstones with intercalated skeletal (oyster-rich) sandy limestones with carbonaceous plant remains of the SS-3. A middle–late Albian age assignment of SS-3 based on regional correlation is supported by strontium isotopic data. This unit marks the first Early Cretaceous marine incursion in the area from the northern Atlantic realm. This is a notable change of the previous palaeogeographical reconstructions which established that the first marine encroachment occurred in the early Aptian and was sourced from Tethysian domains.