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Inflated and compound pahoehoe flows have been identified within the central Paraná Continental Flood Basalts based upon their morphology, surface features, and internal zonation. Pahoehoe flow features have been studied at five localities in the western portion of Paraná State, Brazil: Ponte Queimada, Toledo, Rio Quitéria, Matelândia and Cascavel. We have interpreted the newly recognized flow features using concepts of Hawaiian pahoehoe formation and emplacement that have been previously applied to the Columbia River Basalt and Deccan Plateau. Surface features and/or internal structure typical from pahoehoe lavas are observed in all studied areas and features like inflation clefts, squeeze-ups, breakouts, and P-type lobes with two levels of pipe vesicles are indicative of inflation in these flows. The thinner, compound pahoehoe flows are predominantly composed of P-type lobes and probably emerged at the end of large inflated flows on shallow slopes. The presence of vesicular cores in the majority of compound lobes and the common occurrence of segregation structures suggests high water content in the pahoehoe lavas from the central PCFB. More volcanological studies are necessary to determinate the rheology of lavas and refine emplacement models.

Rcvis ta Brasilcira de Gcocien cias Abstr act GEO LOGY AND Ph·Ph GEOCHRONOLOGY OF I 'ALEOPROTEROZOI C ACID TO INTERM EDIATE GRANI TIC AND VOLCANIC ROCKSThis paper shows :.' 07Pbf206Pb zircon ages of four granitic units of the Mapuera Su ite and :! 07 Pbf206Pb zircon ages of the vo lcanic rock s that enclose these pluto ns. Petrographic, geoc hemical and field data. allow us to d ist inguish two magmatic pulses in the regio n. The first one is respo nsible for the generation of volca nic and granitic rocks of ages between I.X90 an d 1.876 My. The second magmatic pulse gene rated A type gra nites w ith age s rang ing from 1.829 and 1,798 My. Based on field and remote se nsor data, the volcanic rocks o f the Iricoumc Group were divided in three formation s. for which arc pro posed the names Divisor Format ion. Para tso Formation and O uro Prete Formation. Th e ages o fth ese units are around I,X9 and I,XX Ga. The field data indicate s that the Urupi Formation shows intercalations of pyroclastic rocks. These pyroclastic rocks are interp reted as part o f the Paralso Form ation ; co nsequently it locates the Urup i Formation in the Pa leop roterozo ic, suggesting its co rrelation w ith Rora ima Supergnrp. All these litholo g ic units arc associated with a regional , extens iona l, arc ·s hapc d stnrcture, which eneloses the whole Pitinga Province. Gra nitic plutons of the Map uera Su ite occupy the peripheral parts of the structure. \\'hi ch is filled by ctfusive and pyroclastic rocks of the Iricoum e Group, and sedimentary rock s of the Urupi Fonnat ion. The tectoni c setting suggests that the emplacement of volca nic and pyroc lastic rock s or the Iricoume Grou p, in the Pitinga Province, was cont rolled by extensiona l processes of ca ldera co llapse. Su bsequent reactivat ion of the extens ional system allowed the emplacement of the Madeira Suite , in the central port ion of this wide stnrcture.