Dispersed spore assemblages from the Middle-Upper Devonian (mid Givetian to earliest Frasnian) Candás Formation of Northern Spain

The Devonian sequence of the Cantabrian Zone of Northern Spain was deposited around an isolated group of islands (Armorican Terrane Assemblage - ATA) between the Laurussia and Gondwana supercontinents. The Candás Formation (Asturias) and equivalent Portilla Formation (Léon) represent one of the main episodes of reefal development within this sequence. Herein we report, for the first time, palynomorph assemblages recovered from these formations. Palynomorphs recovered from the Portilla Formation are poorly preserved and of high thermal maturity. They are dominated by dispersed spores but also contain abundant and diverse marine elements (acritarchs, chitinozoans and scolecodonts). Due to the challenging preservation, it is not possible to undertake an in-depth study of these assemblages. Palynomorphs recovered from the Candás Formation (members B and D) are exceptionally well preserved and of low thermal maturity. They are dominated by dispersed land plant spores, but also contain rarer marine elements (acritarchs, chitinozoans and scolecodonts). Member B spore assemblages belong with the triangulatus-catillus Assemblage Zone (catillus Subzone) of mid Givetian age. Member D spore assemblages belong with the langii-concinna Assemblage Zone of late Givetian to earliest Frasnian age. This is concordant with independent age dating based on conodonts and invertebrates. The spore assemblages are of North Gondwana aspect but exhibit evidence for distinct endemism. They are dominated by progymnosperm spores indicating a vegetation dominated by arborescent archaeopteridaleans and aneurophytaleans.