LAUSR

Abstract Biostratigraphic analysis integrating spores-pollen and ostracods from boreholes 1AS-8-AM and 1AS-7D-AM, at Atalaia do Norte, Amazonas state, Brazil, allowed to infer Early to Late Miocene for studied sequences. Five palynological zones previously proposed for the Solimoes Formation were identified: Verrutricolporites (Early Miocene), Psiladiporites–Crototricolpites (late Early to early Middle Miocene), Crassoretitriletes (Middle Miocene), Grimsdalea (late Middle to Late Miocene), and Asteraceae (Late Miocene). At the same time, four ostracods (Cyprideis) zones were identified but with limits modified: C. sulcosigmoidalis (late Early to early Middle Miocene); C. caraionae (late Middle to early Late Miocene); C. minipunctata (late Middle to Late Miocene); and C. cyrtoma (early Late Miocene). Furthermore, a new ostracod zone, Cyprideis paralela interval zone (Late Miocene), is formally proposed. Two main bioevents of Cyprideis radiation, related to marine incursions, have been identified: one at late Middle Miocene/early Late Miocene (Grimsdalea zone) and another at Late Miocene (Asteraceae zone). This study attests the viability and importance of using multiple microfossil for more accurate dating and correlation between basins.