This article presents the first map in detail scale for an area covered by Palmas type volcanic rocks in the south border of the eocretaceous Paraná Magmatic Province, south Brazil. The study of the structural features coupled with petrography and geochemistry made it possible to separate these rocks into three main volcanic sequences and recognize their stratigraphy. The older Caxias do Sul sequence rests directly over the first low-Ti basalt flows (Gramado type), and corresponds to the stacking of lobated lava flows, laminar flows and lava domes, mostly emitted as continuous eruptions; only the latest eruptions are intercalated with thin sandstone deposits. These rocks have dacitic composition (~ 68 wt% SiO 2 ) with microphenocrysts of plagioclase and subordinate pyroxenes and Ti-magnetite immersed in glassy or devitrified matrix. A second volcanic sequence, named Barros Cassal, is composed of several lava flows of basaltic andesite, andesitic and dacitic composition (~ 54; ~ 57 and ~ 63 wt% SiO 2 , respectively), with microphenocrysts of plagioclase, pyroxenes and Ti-magnetite. The frequent intercalation of sandstone between the flows attests to the intermittent behaviour of this event. The upper sequence, Santa Maria, is made up of more silica-rich (~ 70 wt% SiO 2 ) rocks occurring as laminar flows, lobated flows and lava-domes. These rocks have rhyolitic composition with microphenocrysts of plagioclase and Ti-magnetite set in a glassy or devitrified matrix with microlites. The structures and textures of all three silicic sequences favor the interpretation that they had a predominantly effusive character, which is thought to be a reflection of the remarkably high temperatures of the lavas (~ 1,000 ºC).Keywords: Volcanic stratigraphy; Silicic lavas; Paraná Magmatic Province; Palmas type. ResumoEste artigo apresenta o primeiro mapa em escala de detalhe de uma área coberta pelas rochas vulcânicas tipo Palmas, na borda sul da Província Magmática Paraná, de idade eocretácica. O estudo das características estruturais, juntamente com a petrografia e geoquímica, permitiu separar as rochas em três sequências vulcânicas principais, reconhecendo a sua estratigrafia. As rochas da primeira sequência, denominada Caxias do Sul, recobrem fluxos basálticos de baixo Ti (tipo Gramado), e correspondem a um empilhamento de derrames lobados, fluxos laminares e lava domos, emitidos por erupções contínuas. O final da atividade vulcânica é marcado por erupções mais intermitentes, permitindo assim a intercalação de delgados depósitos de arenitos. Estas rochas têm composição dacítica (~ 68 %, em peso, SiO 2 ) com microfenocristais de plagioclásio, piroxênios e Ti-magnetita imersos em matriz vítrea ou desvitrificada. A segunda sequência, denominada Barros Cassal, é composta por diversos fluxos de lavas de andesito basáltico, andesito e dacito (~ 54; ~ 57 e ~ 63%, em peso, SiO 2 , respectivamente), com microfenocristais de plagioclásio, piroxênios e Ti-magnetita. A frequente intercalação de arenitos entre os fluxos atesta o comp...

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The Valanginian Stage is marked by a period of global positive δ13C carbon cycle perturbation and biotic crises, which are collectively referred to as the Valanginian event (VE). Many attempts have been made to link the Paraná-Etendeka large igneous province volcanism with the VE. However, currently there is no conclusive proof to support this hypothesis, since the timing and duration of the volcanic activity are not known with sufficient precision. In this study, we significantly revise the time scales of magmatism and environmental impact of the Paraná magmatic province (PMP) in Brazil with new high-precision zircon U-Pb ages from the low-Ti Palmas and high-Ti Chapecó sequences. Our data demonstrate that significant volumes of low-Ti silicic rocks from the PMP erupted rapidly at ca. 133.6 Ma within 0.12 ± 0.11 k.y. The age of the high-Ti Chapecó sequence from central PMP is constrained at ca. 132.9 Ma and thus extends the duration of magmatic activity by ~700 k.y. Our new ages are systematically younger than previous ages and postdate the major positive carbon isotope excursion, indicating that PMP silicic magmatism did not trigger the VE but could have contributed to extending its duration. Within the framework of the stratigraphic column of the PMP, the earliest low-Ti basalts could have been responsible for the VE if they are at least 0.5 m.y. older than the low-Ti silicic rocks dated herein.