The early Miocene lake of Foieta la Sarra-A and its relevance for the reconstruction of the Ribesalbes-Alcora Basin palaeoecology (E Iberian Peninsula)

The Ribesalbes-Alcora Basin (Castell Province, Spain) contains two lower Miocene units that are rich in fossils. The Unit B contains oil-shale and laminated bituminous dolomicrite related to a palaeolake, whereas the Unit C is composed of sandstone and mudstone beds from distal deltaic and shallow lacustrine environments. The La Rinconada and San Chils localities from the Unit B have yielded a fossil assemblage of plants, molluscs, arthropods, and vertebrates, while the localities from the Unit C in the Campisano ravine (Araia/Mas d'Antolino outcrop) are rich in mammalian record. Here we study a new palaeolake deposit of laminated lacustrine limestone beds in the Unit C named Foieta la Sarra-A. This new locality has provided an assemblage of charophytes, terrestrial plants, molluscs, arthropods, and teleosteans. The latter represent the only known fish record from the Ribesalbes-Alcora Basin to date. Although the specimens are generally poorly preserved, the presence of soft-body preservation due to the action of microbial mats at the lake bottom allows considering the Foieta la Sarra-A locality as a Konservat-Lagersttte. The Foieta la Sarra-A palaeolake had a different water chemistry compared to that represented in the Unit B. Its depth was about a few metres and the water level suffered periodic fluctuations. This new locality sheds light on the palaeoenvironmental dynamics of the Ribesalbes-Alcora Basin during the early Miocene and provides a new approach to the palaeoecological reconstruction of the basin.