Middle Ordovician trilobites from the Castillejo Formation, Eastern Iberian Range (NE Spain): taxonomic reappraisal, biostratigraphy, and correlation

Resumen

Middle Ordovician trilobites found in 11 fossil localities from the areas of Alpartir, Aladrén, Luesma and Fombuena (Zaragoza province), and south of Calamocha (Teruel province) are studied. Most records come from the Alpartir Member of the Castillejo Formation, which is dated as Dobrotivian in age (late Darriwilian according to the global scale), with the only exception of two localities that are slightly older, from late Oretanian age (mid−late Darriwilian). In the overlying Sierra Member, three additional localities are recorded, which have estimated age ranges from late early to late Dobrotivian (latest Darriwilian, possibly reaching the Sandbian). A total of 21 different trilobite species were identified including Uralichas hispanicus, Parabarrandia crassa and “Panderia” beaumonti that are recorded for the first time in the Eastern Iberian Range. The main trilobite assemblage from the Alpartir Member belongs to the Placoparia tournemini Biozone, which correlates with numerous areas of southwestern Europe, and here occurs in a biofacies dominated by asaphids. The scarce data derived from the Sierra Member do not allow to distinguish biozones, although the incipient development of a trilobite biofacies adapted to sandy bottoms is recognized, which ends at the top of the Placoparia borni Biozone in the whole of southwestern Europe. The correlation of the trilobite assemblages with those of other formations represented in the Cantabrian, West Asturian-leonese and Central Iberian zones is also discussed, the latter probably related through the enigmatic Central Iberian Arc, a debated orocline of the Iberian Massif.