Sedimentary evolution of coastal-alluvial systems in a rifting basin around the Jurassic-Cretaceous transition (Galve sub-basin, Spain)

The Galve sub-basin (western part of the Maestrazgo Basin) formed part of the Iberian Rift System, a network of rifted basins that evolved on the northwestern Peri-Tethyan Platform during the break-up of Pangaea. The Galve... [ view full abstract ]

The Galve sub-basin (western part of the Maestrazgo Basin) formed part of the Iberian Rift System, a network of rifted basins that evolved on the northwestern Peri-Tethyan Platform during the break-up of Pangaea. The Galve sub-basin developed during a rifting phase that commenced at the end of the Jurassic and lasted until mid-Albian. The main objective of this work is to review the tectosedimentary evolution of this sub-basin around the Jurassic-Cretaceous transition. The studied units record the transition from a middle Tithonian-middle Berriasian syn-rift sequence 1 to the initial stages of the evolution of the upper Berriasian-mid Albian syn-rift sequence 2. Two key lithostratigraphic units are characterized representing different evolutionary stages of two sequences, the Aguilar del Alfambra and the Galve Formations. The Aguilar del Alfambra Formation is bounded by widespread unconformities and is of very variable thickness (0–450 m), controlled by extensional tectonics operating at the climax of syn-rift sequence 1 during the latest Tithonian-middle Berriasian. The unit represents mixed terrigenuos-carbonate sedimentation in transitional environments, from coastal lutitic plains with tide-influenced fluvial channels to carbonate tidal flats and lagoons. Of particular interest are the laminated micritic-peloidal limestones with abundant fenestral porosity, which have common dinosaur footprints. The recorded sequences are stacked in alternating siliciclastic- and carbonate-dominated packages, with a long-term transgressive-regressive facies trend, being the greater marine influence indicated by the intercalation of skeletal-oolitic lagoonal facies. The increase in marine influence could be tentatively related to a sea level rise at the early-middle Berriasian transition. The overlying Galve Formation is of variable thickness (from 0–100 m), and was controlled by extensional tectonics at the initial stage of syn-rift sequence 2, which occurred most probably around the Berriasian-Valanginian transition. The unit represents deposition in a distal alluvial plain, in extensive floodplain areas and related fluvial channels. Fine-grained overbank deposits (lutites and occasional silty limestones) dominate and intercalate cross-bedded sandstones (channels), laminated and/or bioturbated sandstones (levee and crevasse splay deposits) and flash-flood deposits (poorly bedded conglomerates). This alluvial facies have yielded some fossil remains of continental vertebrates (e.g. the sauropod dinosaur Aragosaurus). The lowstand of sea level combined with the break-up and formation of isolated grabens and half-grabens across the Galve sub-basin at the onset of this syn-rift sequence explains its continental character.