Fossil Fungi from Miocene Sedimentary Rocks of the Central and Coastal Amazon Region, North Brazil

Abstract

Samples from outcrops of the Miocene Solimões and Barreiras formations from the central and coastal Amazon regions of Brazil were analyzed palynologically. Assemblages of fossil fungi were identified, and are described herein, and their relevance to paleoenvironmental and paleoclimatic studies in tropical regions discussed. The fungal assemblage comprises four spore groups, 19 species belonging to 12 genera. Additionally, two new species are proposed. The samples from the Solimões Formation contain the following taxa:Mediaverrunites elsikii,Mediaverrunites mulleri,Monoporisporitessp.,Fusiformisporites crabbii, andMulticellites cingulatus. The presence of these suggests river channel margins colonized by freshwater vegetation, where seasonal fluctuations of water table and rainfall produce wetter substrates. The samples from the Barreiras Formation showed higher species and generic diversity than those from the Solimões Formation withHypoxylonites minutus,Hypoxylonsporites ater, Hypoxylonitessp., the new speciesInapertisporites multiporusn. sp.,Pluricellaesporites regularis,Lacrimasporonites levis,Monoporisporites annulatus,Spirotremesporites simplex,Dyadosporites novus,Dyadosporitessp., andMulticellaesporites attenuates. All of these correspond to parasitic fungi from a range of from tropical wetlands.Spegazzinitessp. andDicellaesporites aculeolatus, good indicators of marine influence and mangrove presence, were also identified in the samples from the Barreiras Formation. Furthermore, the fungal spore taxaInapertisporites multiporus,Mediaverrunites elsikii,Mediaverrunites mulleri,Pluricellaesporites regularis, andSpirotremesporites simplexserve as stratigraphic indicators when combined with miospore index taxa such asCrassoretitriletes vanraadshooveni,Grimsdalea magnaclavataandFenestrites longispinosusindicating a Miocene age for these sediments in the Amazon region.