Palaeoenvironmental analysis of the Miocene Arcas del Villar gypsum sequence (Spain), based on palynomorphs and cyprinodontiform fishes

The Arcas del Villar gypsum sequence (Tagus Basin, Central Spain), previously thought to be Eocene or Oligocene in age, is here described in detail for the first time from a stratigraphic and a palaeontological viewpoint. The lower part of the sequence is composed of laminated gypsum and interbedded laminated mudstones and marls; these contain palynomorphs and articulated fish skeletons, sometimes with otoliths in situ. The lithofacies of the sediments indicate that deposition occurred in a meromictic brackish/saline lake environment that evolved into a gypsum marsh. The composition of the palynoflora indicates a probable middle Miocene age and a landscape characterized by prairies of Poaceae and groves of Pinus that had to endure stressful dry seasons. Two new species of fossil fish are described: Paralebias con quensis n. sp. and Valencia arcasensis n. sp., which belong to the families Poeciliidae and Valenciidae respectively. Paralebias con quensis falls into the subfamily Procatopinae, which includes tropical east African species still living in Tanzania, Kenya and Madagascar. Valencia arcasensis belongs to the Valenciidae, the Recent species of which are currently known from south-eastern Spain and western Greece. These fossil fishes bear testimony to a feebly brackish, more or less swampy environment.This work was performed as part of the Spanish Ministery of Economy and Competitiveness research project CGL2011-23438/BTEPeer Reviewe