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The Baie Verte -Brompton Line (BBL), the surface expression of the Taconian suture in the Canadian Appalachian Orogen, extends from southern Quebec to the northeast end of Newfoundland. In the Quebec Appalachians, the BBL was previously located under the post-Taconian cover rocks between the Eastern Townships and Gasp6 Peninsula. New geological data and reinterpretation of gravimetric and aeromagnetic data suggest that the BBL follows the southern edge of the Cambrian-Ordovician rocks of northern Gasp6 Peninsula and is displaced by Middle Devonian strike-slip faults on the southern part of the peninsula. On a pre-Middle Devonian palinspastic map, the BBL is parallel to the Quebec Reentrant -St. Lawrence Promontory and the Appalachian structural front.La ligne Baie Verte -Brompton (BBL), I'expression en surface de la suture taconienne des Appalaches canadiemes, s'Ctend du sud du QuCbec jusqu'i l'extrtmitt nord-est de Terre-Neuve. Dans les Appalaches quCbCcoises, la BBL Ctait auparavant tracke sous les roches de couverture post-taconienne entre 1'Estrie et la pCninsule de GaspCsie. Des nouvelles donnCes gCologiques, de mCme qu'une rCinterprCtation des donnCes gravimktriques et aCromagnCtiques de la GaspCsie, suggkrent que la BBL suit la marge sud des roches cambriennes-ordoviciennes du nord de la GaspCsie et est dCplacCe par des failles coulissantes du dkvonien moyen dans le sud de la ptninsule. Une reconstruction palinspastique prC-coulissage dCvonien moyen de la BBL montre qu'elle est parallkle au rkentrant de QuCbec et au promontoire du Saint-Laurent, de mCme qu'au front structural appalachien.

This contribution provides an overview of the geological setting, stratigraphy, tectono-sedimentary evolution, and paleogeography of the post-Taconian-pre-Carboniferous sequence of the Gasp6 Belt. The sequence has been shaped by two tectonic pulses: the Salinic disturbance that began during the Early Silurian (Telychian) and persisted until the Early Devonian (Pragian), and the ensuing Acadian Orogeny in the Early to Mid-Devonian (Emsian-Eifelian).The shelf and shelf-edge history at the Laurentian margin along the Qurbec Re-entrant-St. Lawrence Promontory can be summarized in five broad phases that resulted from the interplay of tectonics and sea-level change. Phase 1 is a Llandoverian-Wenlockian regressive phase (R~) related to post-Taconian successor basin infilling, which culminated in extensive carbonate platform development. Phase 2 is a late Wenlockian-Ludlovian transgressive phase (T~). Phase 3 corresponds to a later Ludlovian-Pridolian second regressive phase (R2). Phases 2 and 3 were accompanied by extension faulting, block tilting, and the development of reefs, reef complexes and reef tracts along the Gaspr-Trmiscouata shelf. Phase 4 is an Early Devonian phase of accelerated subsidence (transgression T2) affecting the northwestern part (Qurbec Re-entrant area), while the southeastern part (St-Lawrence Promontory area) was previously uplifted as a result of Laurentia colliding with the western margin of Gondwana-related terranes to the south. Phase 5 is the final regression (R3) related to the Acadian Orogeny. RI~SUMI~Cet article pr6sente une vue d'ensemble du contexte grologique, de la stratigraphie, de l'6volution tectono-s6di-mentaire et de la pal6ogrographie de la s6quence post-taconienne h prr-carboniff'ere de la Ceinture de Gasp6sie. I1 se veut un cadre auquel les articles de ce numrro sp6cial des bulletins de la Canadian Petroleum Geology pourront se rattacher. La srquence a 6t6 modelres par deux pulsations tectoniques: la pulsation salinique qui a commenc6 au Tdlychien (Silurien pr6coce) et qui s'est poursuivie jusqu'au Praguien (Drvonien prdcoce); et l'orog6nie acadienne qui a suivi et qui a agi de l'Emsien ~t l'Eifelien (Drvonien pr6coce et moyen). L'histoire du plateau marin et de sa marge, adjacents h Laurentia le long du rrentrant de Qurbec et du promontoire du Saint-Laurent, se rrsume selon cinq grandes phases rrsultant de l'interaction entre la tectonique et les fluctuations du niveau marin. La phase 1 correspond ~t une phase rrgressive (R1) au Llandovrrien-Wenlockien, relire au remplissage du bassin successeur post-taconien; elle a culmin6 avec le d6veloppement d'une plate-forme calcaire tr~s 6tendue. La phase 2 est une phase transgressive (T1) qui eut lieu h la fin du Wenlockien-Ludlovien, alors que la phase 3 correspond ~t une seconde rrgression (R2) h la fin du Ludlovien-Pridolien. Ces deux derni~res phases ont 6t6 accompagn6es d'une tectonique d'extension qui a dissrqu6 le plateau en blocs basculrs sur lesquels se sont implant6s et d6velopp6s J GIRGAB. Groupe interuniversitaire de Rec...

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The principal faults of southeastern Gaspé Peninsula in Quebec consist of a central high-strain zone that is characterized by mainly ductile deformation structures and bordered by low-strain zones each dominated by brittle deformation structures. The overall geometry of shear fractures within the low-strain zones is quite similar to the expected geometry of Riedel shear fractures. The brittle structures overprint the dominant C–S-type fabric of the high-strain zone, which implies that brittle deformation outlasted ductile deformation. The asymmetry of local micro- to meso-scale deformation features along the fault zones reflects the non-coaxiality of the shear. Other features described within the fault zone (stylolitic cleavage, shear bands, and reverse faults) are evidence for a component of shortening perpendicular or oblique to the fault zone. The geometry of the Grand Pabos fault zone (GPFZ), a major fault of southern Gaspé, indicates that deeper seated fault rocks (high-strain zone) have been brought up to higher crustal levels and are presently in contact with brittlely deformed fault rocks (low-strain zone). The proposed model for the evolution of the GPFZ involves Early to Late Devonian, dextral, transcurrent movement accompanied by relatively minor amounts of vertical slip within a dextral transpressive regime. The main pulse of the Acadian orogeny in Gaspé is restricted to the Devonian and therefore occurred later than elsewhere in the Canadian Appalachians.

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...

This field trip guidebook presents a synthesis of the lower to middle Paleozoic stratigraphic architecture and paleogeographic scenarios for the sedimentary basins in southern Québec. The field trip will provide an opportunity to examine the Upper Ordovician Utica Shale and Lorraine Group flysch that were deposited in the Taconian foreland basin of southern Quebec. Cores presenting some aspects of the lateral variability of the internal facies architecture of the Utica will be examined during the first day whereas visits to key outcrops located in the Québec City area are planned during the second day to look at the overall Upper Ordovician stratigraphic architecture and primary facies distribution.