The Pedra de Fogo Formation of the Parnaíba Basin, Northern Brasil is a sedimentary unit that has one of the most important sedimentary records of the early Permian (Cisuralian), characterized mainly by intense silicification. Although previous works have contributed to the understanding of its paleoenvironment, important gaps regarding the sedimentary and paleoclimatic conditions that favored the great concentration and preservation of silica, due to the global changes occurred at the beginning and along of the Permian, still remain inconclusive. Problems as to which sources of silica contributed most to the expressive chert content were never satisfactorily explained. There is no reference to the organic and/or inorganic origins, nor is little known about the conditions and processes that led to the preservation of silica deposits and concretions, as well as the genesis of the known occurrence of carbonates. In order to fill these gaps and/or contribute to a better understanding of the depositional processes in the Pedra de Fogo Formation. This study made facies and stratigraphic analysis, and petrography, complemented by cathodoluminescence image, XRD and SEM-EDS analysis of the permian deposits exposed in the east and southeast portions of the Parnaíba Basin. The main sedimentary facies were grouped into facies associations representative of braided fluvial-aeolian systems from the top Piauí Formation (Carboniferous). This deposits are overlain by lacustrine-sabkha system, wave-dominated nearshore-lacustrine and ephemeral streamsdeposits of the Permian Pedra de Fogo Formation. In general, this unit was deposited in an arid, endorheic lacustrine system, often affected by storm regimes and fed by unconfined flows. Although the arid climate was predominant, this system keeps seasonally, relatively high levels of moisture sufficient to maintain and proliferate its thriving taphoflora, formed mainly by Ferns and Gymnosperms tree. This flora colonized the lakeshore, both in relatively wet and dry periods, as a way to compensate for the low humidity in macroenvironmental. Cyclic variations between the records of organosedimentary structures (microbial mats and stratiform stromatolites) and gymnosperm stem in life position were interpreted as the recurrent migration of the lacustrine shoreline, in response to the expansion and contraction phases of these lakes, triggered by climatic seasonality in the southwestern portion of Pangea. Probably, the flora of the Pedra de Fogo Formation was an important catalyst for the expressive silicification that characterizes this predominantly syndepositional / eodiagenetic unit. This silicification is formed largely by microquartz, under conditions of supersaturation in silica, high enough to preserve the delicate cyanobacteria filaments, as well as pinnules ferns and gymnosperm stems in life position. The occlusion of fractures and dissolution voids (secondary pores), by mosaic megaquartz mosaic, chalcedony spherulites and two generations of chalcedonic overlays, in addition to large crystals (mm) in coarse mosaic calcspar are indicative of polycyclic silicification and circulation of carbonate fluids to mesogenetic zones. The presence of gridwork microtexture indicates that the genesis of silicification is similar to the Magadi chert-type (Rift Valley of Kenya), but from distinct sources, given the absence of volcanic sources associated with Pedra de Fogo deposits.
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