The PMP (Paraná Magmatic Province) is characterized by lava flows of the Early Cretaceous Serra G... more The PMP (Paraná Magmatic Province) is characterized by lava flows of the Early Cretaceous Serra Geral Formation which covers about 75 % of the Paraná Basin (southern and southeastern Brazil), composed of a thick (up to 1600 m) volcanic sequence formed by a succession of petrographically and geochemically distinct units of basic and silicic composition. The whole package must have been emplaced during approximately 3 million years of nearly uninterrupted activity. A few aeolian sandstone layers, indicating arid environmental conditions (the Botucatu Formation), are interlayered in the lower basalts. Above the basalts, the Palmas and Chapecó Members are composed of silicic volcanic rocks (quartz latites, dacites, rhyodacites and rhyolites) and basalts. This paper presents new evidence of sedimentation episodes separating silicic volcanic events, expressed by the occurrence of sedimentary deposits. Interaction between the volcanic bodies and the coeval unconsolidated sediments formed peperites. The sediments were observed between basaltic lava flows and silicic rocks or interlayered in the Palmas-type rocks, between the Chapecó-type rocks and overlying basaltic flows, between silicic bodies of the Palmas and Chapecó types, and interlayered within Palmas-type units. The observed structures indicate that the sediments were still wet and unconsolidated, or weakly consolidated, at the time of volcanism, which, coupled with the sediment features, reflect environmental conditions that are different from those characterizing the
Madeira is a Mio-Pliocene to Holocene hot spot related volcanic island located in the African pla... more Madeira is a Mio-Pliocene to Holocene hot spot related volcanic island located in the African plate. Recent geologic fieldwork (geological mapping, geomorphologic and remote sensing analysis) has lead to the reconnaissance of a fracture pattern and structural control of volcanism. A main WNW-ESE fracture system and two secondary E-W and NE-SE families were identified; these correspond to faults, dike systems, alignment of recent cinder cones, linear geomorphic features and lineaments deduced from satellite imagery analysis. The faults are represented by single fault planes and fault zones, which may show anastomosed or branched map geometry. In section, faults commonly present upward ramifications and steep inclinations either to the north or to the south quadrants. Fault kinematics is still badly constrained, with the scarce slicken side observations indicating dominant normal component. The WNW-ESE Seixal-Machico fault zone, which crosses the whole length of the island, is the major tectonic structure and presents frequent NW-SE branches or en echelon fractures. Madeira Island was built by successive fissural volcanism episodes. The trends of its conduits (represented by dike swarms) and of recent cinder cone alignments are comparable to those of the fault systems, thus indicating important tectonic structure control. Geomorphic features, such as linear fluvial valleys, sea cliffs, and topographic scarps, also suggest important control by structures with the referred trends. Preliminary tectonic data suggests a tensional stress field, with horizontal NNE-SSW minimum compressive stress axis (σ 3 ), stable in time. In fact, the orientation of volcanic and tectonic structures is constant throughout the geologic record. Important mass movements located in the north coast, and spatially related with faults, may have been induced by neotectonic activity. This is a contribution of the CEM/LATTEX/Madeira Regional Government contract "Cartografia Geológica da Ilha da Madeira".
Large-scale gravitational flank collapses of steep volcanic islands are hypothetically capable of... more Large-scale gravitational flank collapses of steep volcanic islands are hypothetically capable of triggering megatsunamis with highly catastrophic effects. Yet, evidence for the generation and impact of collapse-triggered megatsunamis and their high run-ups remains scarce or is highly controversial. Therefore, doubts remain on whether island flank failures truly generate enough volume flux to trigger giant tsunamis, leading to diverging opinions concerning the real hazard potential of such collapses. We show that one of the most prominent oceanic volcanoes on Earth-Fogo, in the Cape Verde Islands-catastrophically collapsed and triggered a megatsunami with devastating effects ~73,000 years ago. Our deductions are based on the recent discovery and cosmogenic (3)He dating of tsunamigenic deposits found on nearby Santiago Island, which attest to the impact of this giant tsunami and document wave run-up heights exceeding 270 m. The evidence reported here implies that Fogo's flank fai...
21 amostras de depósitos pertencentes ao Complexo Vulcânico de Manadas, na ilha de S. Jorge. Os m... more 21 amostras de depósitos pertencentes ao Complexo Vulcânico de Manadas, na ilha de S. Jorge. Os materiais analizados incluem amostras de turfa, madeira, carvão e paleossolos. As idades obtidas indicam idade holocénica para aquela unidade estratigráfica. Os 9 ou 10 episódios vulcânicos datados, em conjunto com as três erupções históricas (1580, 1808 e 1964), revelaram a ocorrência de pelo menos 12 ou 13 erupções nos últimos 5600 anos, separados por períodos médios de dormência inferiores a 470-430 anos. Contudo, um período de recorrência da ordem dos 200 a 300 anos é provavelmente mais realista.
The PMP (Paraná Magmatic Province) is characterized by lava flows of the Early Cretaceous Serra G... more The PMP (Paraná Magmatic Province) is characterized by lava flows of the Early Cretaceous Serra Geral Formation which covers about 75 % of the Paraná Basin (southern and southeastern Brazil), composed of a thick (up to 1600 m) volcanic sequence formed by a succession of petrographically and geochemically distinct units of basic and silicic composition. The whole package must have been emplaced during approximately 3 million years of nearly uninterrupted activity. A few aeolian sandstone layers, indicating arid environmental conditions (the Botucatu Formation), are interlayered in the lower basalts. Above the basalts, the Palmas and Chapecó Members are composed of silicic volcanic rocks (quartz latites, dacites, rhyodacites and rhyolites) and basalts. This paper presents new evidence of sedimentation episodes separating silicic volcanic events, expressed by the occurrence of sedimentary deposits. Interaction between the volcanic bodies and the coeval unconsolidated sediments formed peperites. The sediments were observed between basaltic lava flows and silicic rocks or interlayered in the Palmas-type rocks, between the Chapecó-type rocks and overlying basaltic flows, between silicic bodies of the Palmas and Chapecó types, and interlayered within Palmas-type units. The observed structures indicate that the sediments were still wet and unconsolidated, or weakly consolidated, at the time of volcanism, which, coupled with the sediment features, reflect environmental conditions that are different from those characterizing the
Madeira is a Mio-Pliocene to Holocene hot spot related volcanic island located in the African pla... more Madeira is a Mio-Pliocene to Holocene hot spot related volcanic island located in the African plate. Recent geologic fieldwork (geological mapping, geomorphologic and remote sensing analysis) has lead to the reconnaissance of a fracture pattern and structural control of volcanism. A main WNW-ESE fracture system and two secondary E-W and NE-SE families were identified; these correspond to faults, dike systems, alignment of recent cinder cones, linear geomorphic features and lineaments deduced from satellite imagery analysis. The faults are represented by single fault planes and fault zones, which may show anastomosed or branched map geometry. In section, faults commonly present upward ramifications and steep inclinations either to the north or to the south quadrants. Fault kinematics is still badly constrained, with the scarce slicken side observations indicating dominant normal component. The WNW-ESE Seixal-Machico fault zone, which crosses the whole length of the island, is the major tectonic structure and presents frequent NW-SE branches or en echelon fractures. Madeira Island was built by successive fissural volcanism episodes. The trends of its conduits (represented by dike swarms) and of recent cinder cone alignments are comparable to those of the fault systems, thus indicating important tectonic structure control. Geomorphic features, such as linear fluvial valleys, sea cliffs, and topographic scarps, also suggest important control by structures with the referred trends. Preliminary tectonic data suggests a tensional stress field, with horizontal NNE-SSW minimum compressive stress axis (σ 3 ), stable in time. In fact, the orientation of volcanic and tectonic structures is constant throughout the geologic record. Important mass movements located in the north coast, and spatially related with faults, may have been induced by neotectonic activity. This is a contribution of the CEM/LATTEX/Madeira Regional Government contract "Cartografia Geológica da Ilha da Madeira".
Large-scale gravitational flank collapses of steep volcanic islands are hypothetically capable of... more Large-scale gravitational flank collapses of steep volcanic islands are hypothetically capable of triggering megatsunamis with highly catastrophic effects. Yet, evidence for the generation and impact of collapse-triggered megatsunamis and their high run-ups remains scarce or is highly controversial. Therefore, doubts remain on whether island flank failures truly generate enough volume flux to trigger giant tsunamis, leading to diverging opinions concerning the real hazard potential of such collapses. We show that one of the most prominent oceanic volcanoes on Earth-Fogo, in the Cape Verde Islands-catastrophically collapsed and triggered a megatsunami with devastating effects ~73,000 years ago. Our deductions are based on the recent discovery and cosmogenic (3)He dating of tsunamigenic deposits found on nearby Santiago Island, which attest to the impact of this giant tsunami and document wave run-up heights exceeding 270 m. The evidence reported here implies that Fogo's flank fai...
21 amostras de depósitos pertencentes ao Complexo Vulcânico de Manadas, na ilha de S. Jorge. Os m... more 21 amostras de depósitos pertencentes ao Complexo Vulcânico de Manadas, na ilha de S. Jorge. Os materiais analizados incluem amostras de turfa, madeira, carvão e paleossolos. As idades obtidas indicam idade holocénica para aquela unidade estratigráfica. Os 9 ou 10 episódios vulcânicos datados, em conjunto com as três erupções históricas (1580, 1808 e 1964), revelaram a ocorrência de pelo menos 12 ou 13 erupções nos últimos 5600 anos, separados por períodos médios de dormência inferiores a 470-430 anos. Contudo, um período de recorrência da ordem dos 200 a 300 anos é provavelmente mais realista.
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