MIDDLE-UPPER DEVONIAN PALYNOLOGY FROM THE PONTA GROSSA FORMATION, PARANÁ BASIN, BRAZIL

This work presents a preliminary palynological survey of the acritarch assemblages recovered from 36 samples of well RSP-01-MT in southern Mato Grosso, in central-west Brazil. The studied stratigraphic section, dated as late Eifelian (early part) to latest Frasnian based on miospores, belongs to the Ponta Grossa Formation (the uppermost unit of the Paraná Group), which together with the underlying Furnas Formation constitute the Devonian succession of the Paraná Basin. In the basal part of the studied section (from 358.60 m), represented by fine grained sandstones interbedded with grey siltites, Navifusa bacilla and Tasmanites sp. are predominant. In the middle section (from 348 m) dated to the Givetian, composed of sandstones interbedded with mudstones of varied thickness, there are many palynomorphs, predominantly Navifusa bacilla and subordinate numbers of Winwaloeusia distracta, Triangulina alargada and Maranhites sp. The overlying Frasnian section, dominated by mudstones, yielded an abundant and highly diversified assemblage in its upper portion, characterized by Advenasphaeridium acerosum, Advenasphaeridium australis, Crucidia camirense, Estiastra rhytidoa, Evittia remota, Lunulidia micropunctata, Navifusa bacilla, Duvernaysphaera angelae, Duvernaysphaera tenuicingulata, Dictyotidium sp., Polyedryxium embudum, Polyedryxium sp., Pterospermella sp., Maranhites sp., Maranhites brasiliensis, Maranhites lobulatus, Maranhites mosesii, Maranhites insulatus, Maranhites primus, Maranhites magnum, Pseudolunulidia imperatrizenses and Petrovina cornata. This increase of palynomorph diversity occurred as a reponse to a maximum flooding event in the Late Frasnian, probably related to the major global eustatic sea-level changes which affected the sedimentary deposition during the Devonian.