In western Amazonia, palynology has been the main source of chronological information for the Neogene Period. The Solimões Formation in northwestern Brazil has hundreds of meters of fine-grained rocks that have yielded rich pollen records informing on age and paleoenvironments. Here, we present new pollen data for two boreholes (1-AS-33-AM and 1-AS-37-AM) in the Solimões Basin and one outcrop (Patos) in the Acre Basin, and describe 36 new taxa (two pteridophyte spores and 34 angiosperm pollen) plus one emendation. Palynostratigraphic zonation schemes from Venezuela and Colombia were analyzed critically to provide relative ages for our sections. We found core 33AM to span pollen zones T14 (∼16–14.2 Ma), T15 (14.2–12.7 Ma) and T16 (12.7–7.1 Ma) sensu Jaramillo et al. (2011), while core 37AM spans zones T15? and T16. We also report the widespread occurrence of Cyatheacidites annulatus in outcrops of the Solimões Formation, implying the existence of latest Miocene (∼7 Ma) to Pliocene sedimentation and suggesting ages older than ∼7 Ma for the uppermost sediments of our boreholes. Biostratigraphic relationships also indicate that Echitricolporites mcneillyi and Ladakhipollenites? caribbiensis cannot be used as Pliocene markers as previously assigned. The implications of these results for the palynostratigraphy and paleoenvironmental reconstructions of western Amazonia are discussed.

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