Seismic characterization of the structural front of southern Quebec Appalachians

Séjourné, Stephan; Dietrich, Jane S.; Malo, Michel

doi:10.2113/51.1.29

Cited by 18 publications

(9 citation statements)

References 20 publications

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“…Normal faults also extend into the overlying molasse and flysch units (Figs. 7 b-e), supporting the idea of loadinduced reactivation ahead of the developing Appalachian thrusts (Séjourné et al, 2003).…”

Section: Structure Of the Foreland Basin Area And The Grenville Basementmentioning

confidence: 52%

“…At depth, southeast dipping normal faults (Fig. 6) affect the Grenvillian basement and the St. Lawrence Lowlands sequences (Séjourné et al, 2003;Castonguay et al, 2006;Rodriguez, 2007). Under the Middle-Late Ordovician foreland basin, southeast dipping normal faults form a series of horsts and grabens (Figs.…”

Section: Structure Of the Foreland Basin Area And The Grenville Basementmentioning

confidence: 99%

“…Under the Middle-Late Ordovician foreland basin, southeast dipping normal faults form a series of horsts and grabens (Figs. 7 b-e) that affect thicknesses of the foreland basin units, suggesting syn-sedimentary fault displacement (Séjourné et al, 2003;Castonguay et al, 2006;Rodriguez, 2007). Normal faults also extend into the overlying molasse and flysch units (Figs.…”

Section: Structure Of the Foreland Basin Area And The Grenville Basementmentioning

confidence: 99%

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Effects of Basement Structure, Sedimentation and Erosion on Thrust Wedge Geometry: An Example from the Quebec Appalachians and Analogue Models

Konstantinovskaya

Rodríguez

Kirkwood³

et al. 2009

Bulletin of Canadian Petroleum Geology

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The Taconian fold and thrust belt of the Quebec Appalachians displays typical structures such as inverted normal faults, ramp and flat structures, sub-horizontal detachments, triangle zones and backthrusts. The development of these structures is not, however, consistent along the belt and seems to be spatially related to variations in palaeotopography and stratigraphic architecture of the Middle-Late Ordovician foreland basin, which developed in front of the Taconian tectonic wedge. A triangle zone is bounded by backthrusts in the southeastern limb of the Chambly-Fortierville syncline and by imbricate faults of the thrust wedge parautochthonous units. The triangle zone dies out to the northeast as the basement shallows. Reinterpretation of reflection seismic lines shows that there is a link between the structural geometry of the thrust belt and depth to basement and the presence of pre-existing basement structures. The deflection of frontal thrusts relative to the general SW-NE strike of the orogen occurs over an oblique, deep-seated basement escarpment.In order to better understand factors controlling the formation of structures in the study area, analogue sandbox modelling was used to study thrust systems developed above irregular basement structures and affected by syntectonic sedimentation and erosion. Sand layers were constructed with a décollement level; step-like escarpments were introduced in the model's basement, oriented either parallel or oblique to the shortening direction. Basement depth variations in models controlled the geometry of thrust wedges. Deflection and rotation of frontal detachments was influenced by the presence of an oblique, steep basement escarpment in front of the growing wedge, by gradual changes of sand layer thickness across the ramp and by differential slip along the basal detachment. Deflection developed due to differential forward motion of the hanging wall along the strike of the fault and counter-clockwise rotation about a vertical axis. Syntectonic sedimentation induced forward propagation of flat detachments, resulting in the formation of a piggyback basin. Syntectonic erosion and sedimentation affected the thrust wedge kinematics; a series of backthrusts and/or triangle zones developed at the rear of the wedge. These structures developed above the deeper-seated basement and died out towards basement highs. Our modelling results and geological data support the hypothesis that pre-existing basement structure, syntectonic sedimentation, and erosion could be responsible for the development of triangle zones and frontal thrust deflection in the Quebec Appalachians. RÉSUMÉLa ceinture de plissement et de chevauchement taconique des Appalaches du Québec illustrent des structures typiques, telles que failles normales renversées, rampes, structures plates, décollements subhorizontaux, zones triangulaires et rétrochevauchements. Cependant, l'évolution de ces structures est plutôt inégale le long de la ceinture et, sur le plan spatial, elle semble relative aux variations paléotopogra...

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Section: Structure Of the Foreland Basin Area And The Grenville Basementmentioning

confidence: 52%

Section: Structure Of the Foreland Basin Area And The Grenville Basementmentioning

confidence: 99%

Section: Structure Of the Foreland Basin Area And The Grenville Basementmentioning

confidence: 99%

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Effects of Basement Structure, Sedimentation and Erosion on Thrust Wedge Geometry: An Example from the Quebec Appalachians and Analogue Models

Konstantinovskaya

Rodríguez

Kirkwood³

et al. 2009

Bulletin of Canadian Petroleum Geology

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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: 58%

“…The graben may represent an embayment that accommodated differential shortening relative to the Adirondack and Grenville basements, which acted as a buttress, thus causing strike-slip fault tectonism in the Ordovician platform. In fact, early growth faults active from Cambrian Potsdam Group to Upper Ordovician Trenton deposition were inverted as Taconian décollement ramps (Chalaron and Malo 1998;Séjourné et al 2003) or as strike-slip faults (Faure 1995;Rocher et al 2003). The upper age limit for the ESE-WNW compression is assumed based on observation at site 50 (see Fig.…”

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

confidence: 99%

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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Shallow, old, and hydrologically insignificant fault zones in the Appalachian orogen

Malgrange

Gleeson

2014

JGR Solid Earth

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The permeability of fault zones impacts diverse geological processes such as hydrocarbon migration, hydrothermal fluid circulation, and regional groundwater flow, yet how fault zones affect groundwater flow at a regional scale (1-10 km) is highly uncertain. The objective of this work is to determine whether faults affect regional patterns of groundwater flow, by using radioactive radon and chloride to quantify groundwater discharge to lakes underlain by faults and not underlain by faults. We sampled lakes overlying the Paleozoic Appalachian fold and thrust belt in the Eastern Townships in Québec, and compared our results to a previous study in a crystalline watershed in the Canadian Shield. The field data was analyzed with an analytical geochemical mixing model. The uncertainties of model parameters were assessed in a sensitivity analysis using Monte Carlo simulation, and the difference between lakes tested with statistical analysis. While the model results indicate non-negligible groundwater discharge for most of the lakes in the Paleozoic orogen, the difference between the groundwater discharge rate into the lakes located on faults and the other lakes is not statistically significant. However, the groundwater discharge rate to lakes in the Paleozoic orogeny is significantly higher than lakes that overlay crystalline bedrock, which is consistent with independent estimates of permeability. The rate of groundwater discharge is not significantly enhanced or diminished around the thrust fault zones, suggesting that in a regional scale, permeability of fault zones is not significantly different from the bedrock permeability at shallow depth in this old, tectonically-inactive orogen.

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Seismic characterization of the structural front of southern Quebec Appalachians

Cited by 18 publications

References 20 publications

Effects of Basement Structure, Sedimentation and Erosion on Thrust Wedge Geometry: An Example from the Quebec Appalachians and Analogue Models

Effects of Basement Structure, Sedimentation and Erosion on Thrust Wedge Geometry: An Example from the Quebec Appalachians and Analogue Models

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

Shallow, old, and hydrologically insignificant fault zones in the Appalachian orogen

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