Acritarch-based chronostratigraphic and radiometric calibration of the Cambrian volcanosedimentary Vallehondo and Playón formations in the Cambrian Ossa-Morena Rift, Spain

Abstract The detailed record of diagnostic acritarchs from the volcanosedimentary Vallehondo and Playon formations, bracketed between Cambrian Stage 4 strata bearing trilobite Serrodiscus Guzhangian (Miaolingian) beds with Sao aff. hirsuta, allows establishment a fine acritarch-based chronostratigraphy. Seven interval zones are defined by first successive appearances cosmopolitan index acritarchs, two in Series 2 (Skiagia ciliosa Heliosphaeridium notatum zones) five Miaolingian (Eliasum llaniscum, Cristallinium cambriense, Adara alea, Timofeevia lancarae dubium zones). base E. llaniscum Zone, which approximates appearance Acadoparadoxides cf. mureroensis, marks bioevent close to Wuliuan Stage, includes an episode felsic volcanism upper member Formation. cambriense Zone is underlain rhyolites ignimbrites previously dated at ca. 505 Ma. alea concurs last volcanic episodes Formation here 500.9 ± 0.9 Ma. maximum diversification (A. alea–T. coincides onset basaltic pillow lava flows reflecting major rifting episode. recognized zonation applicable Acado-Baltic (biogeographic) Province, reinforces great value chronostratigaphy. new biostratigraphic data confirm absence Furongian study area late Drumian–Guzhangian age C. for one main syn-rift recorded Ossa-Morena Rift.