Stratigraphy and volcanic facies architecture of the Torres Syncline, Southern Brazil, and its role in understanding the Paraná–Etendeka Continental Flood Basalt Province

Waichel, Breno Leitão; Lima, Evandro Fernandes de; Viana, Adriano R.; Scherer, Claiton Marlon dos Santos; Bueno, Gilmar Vital; Dutra, Gabriel

doi:10.1016/j.jvolgeores.2011.12.004

Cited by 84 publications

(51 citation statements)

References 30 publications

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“…The effusive origin for the same rock association was assumed (Bellieni et al 1986;Comin-Chiaramonti et al 1988;Henry & Wolff 1992;Umann et al 2001;Waichel et al 2012;Polo & Janasi 2014) and the volcanic conduits of lava flows were described in the Northeastern portion of Rio Grande do Sul State .…”

Section: Introductionmentioning

confidence: 83%

“…In a wide scale, the acidic flows in Torres Syncline are described as occurrences of lava dome fields and tabular flows representing two main events (AVE I and AVE II, Waichel et al 2012). In a more detailed scale of work, there is a more complex arrangement of facies architecture, therefore lava domes and flows can be individually divided into massive pitchstones, flow-banded vitrophyres, tabular-foliated flows and auto-clastic breccia.…”

Section: Field and Petrographic Backgroundmentioning

confidence: 99%

“…The stratigraphic reference to this part of the Paraná-Etendeka CFB is defined as Serra Geral Formation (SGF), which is a tholeiitic volcanic rock association, 1,700 m thick, with a great proportion of basic and less representative intermediate to acidic volcanic rocks . Waichel et al (2012) described the facies architecture of SGF in the Torres Syncline region, identifying five distinct volcanic episodes: Basic Volcanic Episode I (BVE I) that covers Botucatu paleoerg with compound pahoehoe flows; BVE II representing the volcanic climax and composed of ~ 500 m tabular-classic simple pahoehoe flows; Acidic Volcanic Episode I (AVE I), which is composed of acidic lava dome-field facies association; BVE III that comprises 'a'a flows with tabular/lobate escoriaceous facies association; and AVE II represented by acidic tabular facies. Recently, detailed studies of basic lavas from the BVE III identified a four-part structure with internal characteristics typical of rubbly pahoehoe lavas (Rossetti et al 2014).…”

Section: Introductionmentioning

confidence: 99%

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The role of viscosity in the emplacement of high-temperature acidic flows of Serra Geral Formation in Torres Syncline (Rio Grande do Sul State, Brazil)

Simões¹,

Rossetti²,

Lima³

et al. 2014

Braz. J. Geol.

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ABSTRACT:The acidic flows from Serra Geral Formation in Torres Syncline, Rio Grande do Sul, Brazil, are on the top of a volcanic sequence composed by a complex facies association of compound, simple and rubbly pahoehoe basic flows, acidic lava domes, and tabular acidic lava flows. The origin and emplacement conditions of the acidic volcanic rocks are discussed in this paper based on petrology, on calculated apatite saturation thermometry temperatures, and on estimated viscosity data. The liquidus temperatures for metaluminous rhyodacite to rhyolite samples are about 1,067.5 ± 25ºC in average. The viscosity (η) values vary from 10 5 to 10 6 Pas for anhydrous conditions, suggesting the emplacement of high-temperaturelow-viscosity lava flows and domes. The occurrence of acidic lava domes above simple pahoehoe flows as flow-banded vitrophyres was under low effusion rates, in spite of their high temperature and low viscosities, which are reflected in their small height. The emplacement of lava domes has continued until the eruption of rubbly pahoehoe flows and the geometry of these deposits rugged the relief. Presence of tabular acidic lava flows covering the landscape indicates that it was under high effusion rates conditions and such flows had well-insulated cooled surface crusts. The capacity to attain greater distances and overpass relief obstacles is explained not only by high effusion rates, but also by very low viscosities at the time of emplacement.

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Section: Introductionmentioning

confidence: 83%

Section: Field and Petrographic Backgroundmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The role of viscosity in the emplacement of high-temperature acidic flows of Serra Geral Formation in Torres Syncline (Rio Grande do Sul State, Brazil)

Simões¹,

Rossetti²,

Lima³

et al. 2014

Braz. J. Geol.

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“…They were followed by the Esmeralda type basalts, which exhibit, towards the top, intercalations with silicic volcanic rocks of the low-Ti Palmas type (dacites and rhyolites; Bellieni et al, 1986;Garland et al, 1995;Nardy, 1995;Nardy et al, 2008;Waichel et al, 2012).…”

Section: Stratigraphymentioning

confidence: 99%

“…In a more recent study, Waichel et al (2012) presented stratigraphic cross-sections along the Torres syncline (southern border of the PMP), identifying two main silicic volcanic manifestations (without correlating them to low-Ti magma types defined in the literature), and proposed that the first (AVE-I) resulted in a coalescent lava-dome field, whilst the second (AVE-II) would correspond to tabular flows. Basaltic floods (their BE-III) occur interbedded with these deposits.…”

Section: The Palmas Type Silicic Volcanism: Geochemistry and Stratigrmentioning

confidence: 99%

Volcanic stratigraphy of intermediate to acidic rocks in southern Paraná Magmatic Province, Brazil

Polo

Janasi

2014

Geol. USP, Sér. cient.

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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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Brittle reactivation of ductile shear zones in NW Namibia in relation to South Atlantic rifting

2015

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Rifting has occurred worldwide along preexisting mobile belts, which are therefore thought to control rift orientation on a large scale. On a smaller scale, shear zones within mobile belts are reactivated as rift faults. In NW Namibia, shear zones of the Neoproterozoic Kaoko Belt run subparallel to the present-day continental passive margin and are inferred to have been reactivated during the opening of the South Atlantic Ocean. However, the extent of this reactivation and the influence of the reactivated shear zones on South Atlantic rifting are largely unknown. A combined remote sensing and field study was conducted to quantify offsets that are a direct function of shear zone reactivation. The shear zones of the Kaoko Belt are partly overlain by the Paraná-Etendeka volcanic rocks, which were emplaced shortly before or simultaneously to the Atlantic rifting. Faulting within these volcanic rocks can be linked to synrift or postrift movements. Along the shear zones, downfaulting of the basalts is widespread along listric faults where half-graben form in the hanging wall. At three sites we could determine vertical offsets of~1180 m,~470 m, and~70 m. Although many shear zones were reactivated as faults, these are isolated, and offsets are small, suggesting that reactivation occurred only as a side effect of the rifting and that the Kaoko Belt shear zones have not exerted a significant influence on the rift orientation.

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Stratigraphy and volcanic facies architecture of the Torres Syncline, Southern Brazil, and its role in understanding the Paraná–Etendeka Continental Flood Basalt Province

Cited by 84 publications

References 30 publications

The role of viscosity in the emplacement of high-temperature acidic flows of Serra Geral Formation in Torres Syncline (Rio Grande do Sul State, Brazil)

The role of viscosity in the emplacement of high-temperature acidic flows of Serra Geral Formation in Torres Syncline (Rio Grande do Sul State, Brazil)

Volcanic stratigraphy of intermediate to acidic rocks in southern Paraná Magmatic Province, Brazil

Brittle reactivation of ductile shear zones in NW Namibia in relation to South Atlantic rifting

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