Brachiopods from the Albian–Cenomanian transition (Cretaceous) of the Eastern Prebetic (South-Iberian paleomargin)

Abstract

Brachiopod communities in the Albian–Cenomanian transition from the Eastern Betic Ranges were previously accredited and frequently considered as biochronostratigraphical tools to dating the hemipelagic successions of this timespan by correlation with other neighboring Tethyan basins. However, the knowledge of these mid-Cretaceous assemblages in this part of the South-Iberian paleomargin remained poorly understood so far. Brachiopod communities of this timespan are commonly dominated by homeomorphic terebratulides and asymmetrical multicostate rhynchonellides, these later recurrently attributed to Cyclothyris difformis due to the strong external similarity with their NW-European counterparts, and consequently, the Prebetic deposits were customarily assigned to the Cenomanian stage. In this work, the detailed analysis of the assemblages from the taxonomic and biostratigraphical standpoints allows for the identification of a new brachiopod fauna endemic to the Eastern Prebetic Domain, inhabiting platform environments with frequent terrigenous inputs in transition to the more offshore areas. This analysis has led to the formal description of two new species, Cyclothyris bitririca and Sellithyris binalubensis, together with Cyclothyris ementitum, recently erected as new species, plus Psilothyris hispanica, both endemic to the Prebetic area as well. The successive faunal replacement between two defined assemblages enclosing this fauna is a useful regional biomarker around the Albian–Cenomanian boundary. The bioevents typifying this turnover consist of a rhynchonellide taxa short-term replacement and the burst on diversity and abundance of smooth, nearly homomorphic terebratulides for the levels just underlying the base of the Cenomanian stage.