A deep structural profile across the Appalachians of southern Quebec

Julien, Pierre; Slivitsky, Anne; Feininger, Tomás

doi:10.1130/mem158-p103

Cited by 51 publications

(26 citation statements)

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“…1). The former represent the accumulation of sediments on oceanic crust (Laurent 1975;St-Julien and Hubert 1975), which is followed to the southeast by the St. Victor synclinorium and the Ascot-Weedon Formation, which are the remains of a synchronous island arc (St-Julien et al 1983). Southeast of this are rocks of the CVGS, composed mainly of the St. Francis Group, which is a thick sequence of sandstones, slates, and limestones, unconformably above the Cambro-Ordovician Ascot-Weedon Formation volcanic rocks.…”

Section: Introductionmentioning

confidence: 99%

“…Southeast of this are rocks of the CVGS, composed mainly of the St. Francis Group, which is a thick sequence of sandstones, slates, and limestones, unconformably above the Cambro-Ordovician Ascot-Weedon Formation volcanic rocks. The St. Francis Group includes the Compton Formation, a monotonous turbiditic sequence of alternating grey and black shales and fine-grained laminated sandstones (St-Julien et al 1983), which is host to the Scotstown, Winslow, and Ste-CCcile plutons. The Aylmer pluton was intruded at the contact between the rocks of the Ascot-Weedon and Compton formations.…”

Section: Introductionmentioning

confidence: 99%

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U–Pb and Rb–Sr geochronology of Acadian plutonism in the Dunnage zone of the southeastern Quebec Appalachians

Simonetti¹,

Doig²

1990

Can. J. Earth Sci.

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U-Pb zircon and (or) titanite or monazite ages have been obtained for five major, undeformed, calc-alkaline plutons of the Appalachians of southeastern Quebec. These are interpreted as ages of crystallization for the Scotstown (384 * 2 Ma), Lac aux Araignkes (383 -C 3 Ma), Winslow (377 * 7 Ma), Aylmer (375 + 3 Ma), and Ste-Ctcile (374 2 Ma) plutons. Many other titanite samples gave 2 0 6~b / 2 3 8~ dates that are 2-16 Ma younger than the concordant zircon dates from the same samples, and this is probably the result of Pb loss. Variation in 207~b/2"~b ages of titanite from some samples is attributed to incorrect common Pb correction.Rb-Sr data for the same plutons show considerable isotopic heterogeneity and correspondingly high errors in ages. The isotopic heterogeneity is likely caused by postsolidification metasomatic alteration by host rock fluids. Where the scatter is least (Ste-Ckcile), the Rb-Sr age (364 * 14 Ma) is similar to the U-Pb mineral age (374 * 2 Ma). The 87Sr/86~r initial ratios range from 0.7065 to 0.710 and are probably related to the source of the magmas. The relatively high initial ratios and the peraluminous nature of the plutons preclude a significant mantle contribution to the magmas. These undeformed plutons are probably the result of melting of the lower continental crust near the end of crustal thickening caused by compression during the Acadian Orogeny . Les kges U-Pb sur zircon et (ou) titanite ou monazite ont kt6 dkterminks pour cinq grands plutons calco-alcalins, non dkformks, des Appalaches du sud-est du Quebec. Les rksultats sont interprktks c o m e reprksentant l'lge de cristallisation des plutons de Scotstown (384 + 2 Ma), Lac aux Araignkes (383 * 3 Ma), Winslow (377 * 7 Ma), Aylmer (375 * 3 Ma) et Ste-Ctcile (374 + 2 Ma). Plusieurs autres tchantillons de titanite ont fourni des lges 2 0 6~b / 2 3 8~ plus jeunes de 2 ? I 16 Ma que ceux fournis par les zircons concordants qui rovenaient des memes tchantillons, cette diffkrence rtsulte probablement d'une perte de Pb. La variation dans les ages '~~P b i~~P bsur titanite observke pour certains Cchantillons est amibuke a une e m u r dans la correction du plomb commun.Les donnkes Rb-Sr obtenues sur les m&mes plutons indiquent une trks grande hktkrogknkitk isotopique, par conskquent, des erreurs klevkes dans les Lges correspondants. L'hktkrogknkitk isotopique rksulte probablement d'une altkration mktasomatique, aprks cristallisation, par les fluides de la roche renfermant les isotopes. Dans le cas de dispersion minimale (Ste-Ckcile), 1'Lge Rb-Sr (364 * 14 Ma) est voisin de l'kge U-Pb fourni par les minkraux (374 * 2 Ma). Les rapports initiaux 87Sr/86~r varient de 0,7065 a 0,710, ils sont relies probablement aux magmas parentaux. Les rapports initiaux relativement klevks et la composition peralumineuse des plutons tcartent toute hypothkse d'une contribution significative de magmas dkrivant du manteau. Ces plutons non dkformks sont issus vraisemblablement d'une fusion de la croiite infkrieure, prks d'une zone d'kpaississement crustal crk...

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

U–Pb and Rb–Sr geochronology of Acadian plutonism in the Dunnage zone of the southeastern Quebec Appalachians

Simonetti¹,

Doig²

1990

Can. J. Earth Sci.

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“…Taconian thrusts, and the dips of mesoscopic faults are similar to those on shallow-dipping regional thrusts, as interpreted on the seismic profile of Line 2001 (St-Julien et al 1983;Spencer et al 1989;Castonguay et al 2001b;Séjourné et al 2003). The σ1 axes are nearly perpendicular to the regional trends of Taconian folds and faults and their directions are similar throughout the external domain.…”

Section: Taconian Stress In the Humber Zone And St Lawrence Lowlandsmentioning

confidence: 80%

Reconstruction of Taconian and Acadian paleostress regimes in the Quebec and northern New Brunswick Appalachians

Faure¹,

Tremblay²,

Malo³

2004

Can. J. Earth Sci.

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A numerical analysis of fault populations was applied in the Quebec and northern New Brunswick Appalachians to characterize paleostress fields attributed to the Taconian and Acadian orogenies. The first brittle deformation documented in the external domain of the Humber Zone is associated with the thin-skinned tectonics of the Taconian orogen. The Taconian brittle deformation, characterized by north-south to NE-SW reverse conjugated brittle faults, evolved under a pure shear compressional regime (vertical σ3 axes) with σ1 axes oriented ESE-WNW. The ENE-WSW dextral and NW-SE sinistral faults that are observed in the St.Lawrence Lowlands are also attributed to Taconian compression. The first brittle deformation recognized in the Dunnage Zone and the Gaspé Belt is attributed to an ESE-WNW compression during the Acadian Orogeny. In the Dunnage Zone of southern Quebec, the Acadian paleostress axes are similar to the directions of σ1 axes and to the pure shear compressional regime computed for the Silurian and Devonian rocks of the Gaspé Belt. In the Gaspé Peninsula, the Acadian stresses are oriented ESE-WNW and are mechanically compatible with transpressional regimes. Reverse brittle faults and pure shear stress are identified along regional and secondary sets of NE-SW brittle faults, whereas a strike-slip stress regime is reconstructed along major east-west faults. In the Humber Zone of the Quebec Appalachians, a second compression is identified. It is characterized by conjugate ENE-WSW dextral and NW-SE sinistral strike-slip faults that crosscut Taconian thrust faults. This late deformation event is attributed to a distal expression of the Acadian Orogeny. 634Résumé : Les contraintes taconiennes et acadiennes reliées aux failles cassantes ont été reconstituées dans les Appalaches du Québec et du nord du Nouveau-Brunswick. La première phase de déformation cassante reconnue dans le domaine externe de la zone de Humber est associée à la tectonique plicative de faible profondeur de l'orogenèse taconienne. Elle est caractérisée par des failles cassantes N-S à NE-SO, inverses et conjuguées, formées en cisaillement pur (axes σ3 verticaux) sous des axes σ1 orientés ESE-ONO. Les failles de décrochement observées dans la plate-forme du Saint-Laurent sont aussi corrélées à la compression taconienne. La première phase de déformation cassante reconnue dans la zone de Dunnage et la Ceinture de Gaspé est attribuée à l'orogenèse acadienne et à une compression également orientée ESE-ONO. Dans la zone de Dunnage du sud du Québec, les paléocontraintes acadiennes reconstituées sont similaires aux directions des axes σ1 et au régime en cisaillement pur identifiés dans la Ceinture de Gaspé. En Gaspésie, les contraintes acadiennes sont orientées ESE-ONO et sont compatibles avec un régime en transpression. Des failles inverses et des contraintes en cisaillement pur sont reconnues le long des failles régionales et secondaires NE-SO, alors que des failles décrochantes et un régime en décrochement sont documentés le long des failles régionale...

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“…La présence de quelques fragments de ponce (?) et l'absence d'arrondi des grains, notamment du feldspath et du quartz, suggèrent que les mécanismes d'érosion n'ont pas joué un rôle aussi important dans la genèse de ces volcanoclastites (Cousineau et St-Julien, 1994 St-Julien et al, 1983;St-Julien, 1987;Cousineau, 1990) renferme une interstratification de lits centimétriques d'une argilite noire et de lits centimétriques à métriques de volcanoclastites noires (Cousineau et St-Julien, 1994 (Riva, 1974;St-Julien, 1970, 1987 L'abondance des pyroclastes dans le faciès principal des volcanoclastites felsiques (Cousineau, 1994) supporte un emplacement sous forme de coulée de masse sous-marine de débris pyroclastiques (Stix,1991).…”

Section: Groupes De Black River Et Trentonunclassified

Sédimentologie des volcanoclastites de la formation de Beauceville, Appalaches du Québec /

Tremblay¹

1997

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The Beauceville Formation of the Magog Group is mainly composed of graptolitebearing pelagic mudstone and volcaniclastic rocks, which were deposited in a fore-arc basin during the Ordovician. The volcaniclastic rocks of the Beauceville area, their transport and depositional mechanisms are not well known.On the basis of sedimentary structures, composition, grain size and delicate textures of debris, four distinct lithofacies were identified. The massive lapilli tuff-tuff faciès A is composed of: i) 2-5m-thick, fines-poor, massive lapilli tuffs (MLT) that are either massive or graded and ii) 1-1 lm-thick, fines-poor, massive crystal-rich tuffs (MCT) with normal or inverse grading. Faciès B, represented by the stratified and laminated lapilli tuff-tuff faciès, is divided in two subfacies: i) 0,5-lm-thick, fines-poor, stratified lapilli-tuffs (SLT) are composed of 5-40cm-thick, poorly graded layers and ii) l-10m-thick, fines-poor, stratified and laminated crystal-rich tuffs (SLCT) show 5-10cm-thick parallel stratified layers with normal grading and parallel laminae. Faciès C is characterized by the massive finer-grained tuff faciès (MFT) composed of 0,4-5m-thick beds rich en shards. Faciès D, a laminated finer-grained tuff faciès (LFT) is l-7m-thick shard-rich unit composed of 2 mm-6 cm-thick laminae and beds.The four lithofacies are organized into two distinct faciès associations that each display a well defined doubly graded sequence. Faciès association 1 with the assemblage MCT->SLCT->MFT->LFT is 28m-thick, whereas faciès association 2 characterized by the assemblage MLT->SLT->MCT->SLCT->LFT is 24m-thick. Both faciès associations rest on pelagic mudstone suggesting that they could be either lateral or downslope equivalents. Based on the grain size distribution, faciès association 1 is probably the downslope or lateral (distal ?) equivalent of faciès association 2.Abundance of delicate shards and pumice in these two faciès associations, the good sorting of the framework constituents and the absence of pelagic sedimentary interbeds as well as the doubly graded sequence favour direct sedimentation from an explosive phreatomagmatic or phreatoplinian eruption that was probably subaqueous due to the bounding pelagic sedimentary faciès. Faciès A is interpreted as partially laminar flow deposits, whereas faciès B reflects a more turbulent flow deposition. The faciès C and faciès D are either subaqueous fallout deposits related to waning eruptive stages or ashturbidites produced by elutriating fine ash from initialy high-concentration flows.

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A deep structural profile across the Appalachians of southern Quebec

Cited by 51 publications

References 0 publications

U–Pb and Rb–Sr geochronology of Acadian plutonism in the Dunnage zone of the southeastern Quebec Appalachians

U–Pb and Rb–Sr geochronology of Acadian plutonism in the Dunnage zone of the southeastern Quebec Appalachians

Reconstruction of Taconian and Acadian paleostress regimes in the Quebec and northern New Brunswick Appalachians

Sédimentologie des volcanoclastites de la formation de Beauceville, Appalaches du Québec /

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