The Late Devonian palynology of the Llanos Orientales Basin, Colombia

Diverse and rich assemblages composed of spores and organic-walled microphytoplankton are reported from fifteen subsurface samples of the SM-4 well in the Llanos Orientales Basin, Colombia. The palynoflora includes 32 species of spores, 23 acritarchs, 9 prasinophyte phycomata along with 9 species of chitinozoans and indeterminate scolecodonts. These are the first Late Devonian palynological assemblages to be described and illustrated in detail from Colombia. Based on global stratigraphic ranges, a Frasnian-Famennian age is proposed for the studied succession, although diagnostic late Famennian species are notably absent. Teichertospora torquata and Hystricosporites multifurcatus first occurrences allow for the assignment of the uppermost samples to the Famennian, while the presence of Ancyrospora spp., Evittia geometrica, Puteoscortum limai, Samarisporites triangulatus and Verrucosisporites bulliferus characterize the Frasnian. Chitinozoans and acritarchs confirm a Frasnian age for most of the analyzed samples, enabling correlation with assemblages described in Brazilian basins. It is suggested that the assemblages are approximately time-equivalent to the Teichertospora torquata-Auroraspora pseudocrista (late Frasnian- late middle Famennian) and Verrucosisporites bulliferus-Geminospora piliformis (early middle Frasnian) Brazilian zones. The uppermost strata in the studied section were deposited in shoreline marine environments, while below 822.9 m, microplankton diversity indicates a transition from nearshore to offshore conditions.