Trilobite biostratigraphy of the Marianian (Cambrian Series 2) from Seville and Badajoz provinces (Zafra-Alanís Domain, Ossa-Morena Zone, Spain): a review

Abstract

The Cambrian outcrops within the Zafra-Alanís Domain, southwest Iberia contain the type localities of several trilobite genera, including Alanisia, Saukianda, Perrector, Eops, Andalusiana, Protaldonia, and nine trilobite species. These fossils are attributed to the Marianian regional Stage, spanning from the upper Stage 3 to the lower Stage 4 of Cambrian Series 2. Despite their significance, the biostratigraphy of these outcrops has remained understudied due to the scarcity of continuous stratigraphic sections and the lack of comprehensive biostratigraphic research in this region. In this work, we present a refined trilobite biostratigraphic framework by examining ten newly established stratigraphic sections bearing trilobite fossils of the Zafra-Alanís Domain, on the Northern flank of the Olivenza-Monesterio Antiform, spanning across the Badajoz and Seville provinces. This framework constitutes the foundation for future zonation of the Marianian Stage and contributes to a more precise understanding for international correlation. The Cambrian tectonosedimentary blocks of the Ossa-Morena Zone, formed due to the rifting process in southwestern Iberia during Cambrian times, extend into southwestern Spain and eastern Portugal. A revised delineation of these blocks has been carried out, including a new outline of the Feria Fault, now identified as the Guadalcanal-Assumar Fault. In addition, the stratigraphic and palaeontological analysis of the Cambrian outcrops in the Seville province (Sierra Morena de Sevilla Natural Park - UNESCO Global Geopark) allows their inclusion within the recently defined Viar-Benalija basin.