Bedrock geological mapping and basin studies in the Gulf of St. Lawrence

Sanford, B V; Grant, A C

doi:10.4095/129048

Cited by 21 publications

(15 citation statements)

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“…Most of the deformation of the frontal thrust sheets of the Appalachians has been traditionally attributed to the Middle-Late Ordovician Taconian orogeny (St-Julien and Hubert, 1975;Tremblay and Pinet, 1994;Pinet and Tremblay, 1995). The imprint of younger tectonic events, recorded by both extensional and compressional structures, is, however, increasingly documented on the basis of field (Lynch, 1998;Rocher et al, 2003), seismic (Sanford and Grant, 1990), radiochronologic (Glasmacher et al, 2003;Sasseville, 2006) and maturation (He´roux and Bertrand, 1991) data.…”

Section: Bedrock Geological Background and Hydrocarbon Potentialmentioning

confidence: 93%

Surface and subsurface signatures of gas seepage in the St. Lawrence Estuary (Canada): Significance to hydrocarbon exploration

Pinet

Duchesne

Lavoie

et al. 2008

Marine and Petroleum Geology

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Section: Bedrock Geological Background and Hydrocarbon Potentialmentioning

confidence: 93%

Surface and subsurface signatures of gas seepage in the St. Lawrence Estuary (Canada): Significance to hydrocarbon exploration

Pinet

Duchesne

Lavoie

et al. 2008

Marine and Petroleum Geology

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“…Instead, it is best to view the area between Sept-Îles and the tip of the Newfoundland promontory as the result of a transform fault, as suggested by Thomas (1977). The trace of this fault could be a currently seismogenic feature that extends in a south-southeast direction into the St. Lawrence River from Sept-Îles and that is interpreted to have been active during the Paleozoic (Sandford and Grant 1990). …”

Section: Limits Of the Quebec Reentrantmentioning

confidence: 95%

Lower Paleozoic configuration of the Quebec reentrant based on improved along-strike paleogeography

Cousineau¹,

Longuépée²

2003

Can. J. Earth Sci.

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An improved paleogeography of the Quebec reentrant has been achieved by examining the nature and distribution of major sediment buildups within this reentrant. The Quebec reentrant has one side produced by rift faults and one side by a major transform fault. The Oak Hill Group was deposited near a triple-rift zone. Clastic sediments of this group formed a large delta that was fed by a major river flowing in the rift valley of the Ottawa graben. The delta must have prograded on a gentle slope platform. No other thick deltaic deposits are known towards the northeast. Instead, facies analyses favor the existence of a promontory near Québec. Still farther to the northeast, the Saguenay graben was not the product of a triple-rift junction. However, it served to funnel sediments to a deep-sea fan, and the adjacent platform was narrow with a steep slope. The lateral distribution of sediments from the Ordovician Taconic orogeny can be explained by this improved paleogeographic reconstruction. The configuration of the Quebec reentrant required the arc to move into the reentrant. The Taconian tectonic wedge progressively accreted the thick sediment buildups that were the Oak Hill delta and the Bas-du-Fleuve deep-sea fan. This allowed them to act as new barriers to orogenic sediment dispersal as the orogeny proceeded.Résumé : La paléogéographie du rentrant de Québec a été améliorée par l'examen de la nature et la distribution d'accumulations majeures de sédiments dans ce rentrant. Un côté du rentrant de Québec a été formé par des failles d'effondrement et un autre côté a été formé par une faille transformante majeure. Le Groupe de Oak Hill a été déposé près d'une zone à effondrement triple. Les sédiments clastiques de ce groupe ont formé un large delta qui était nourri par une grande rivière s'écoulant dans la vallée d'effondrement du graben d'Ottawa. Le delta devait avancer sur une plate-forme à faible pente. Aucun autre dépôt deltaïque épais n'est connu vers le nord-est. Au lieu, les analyses de faciès favorisent l'existence d'un promontoire à proximité de la Ville de Québec. Situé encore plus vers le nord-est, le graben du Saguenay ne résulte pas d'une jonction d'effondrement triple. Toutefois, il servait à canaliser des sédiments vers un éventail marin profond et la plate-forme adjacente était étroite avec une pente abrupte. La distribution latérale des sédiments de l'orogenèse taconienne (Ordovicien) peut être expliquée par cette reconstruction paléogéographique améliorée. La configuration du rentrant de Québec exige que l'arc ait bougé pour se déplacer dans le rentrant. Le coin tectonique taconien a progressivement accrété les accumulations épaisses de sédiments qui formaient le delta de Oak Hill et l'éventail marin profond de Bas-du-Fleuve. Cela leur a permis d'agir comme de nouvelles barrières à la dispersion des sédiments orogéniques alors que l'orogenèse était en cours.[Traduit par la Rédaction] Cousineau and Longuépée 219

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“…Much of the southern flank of the New York promontory is covered either by water, Pleistocene deposits, Coastal Plain sediments, or Mesozoic basins. Much of the southern flank of the St. Lawrence promontory is covered by Carboniferous sedimentary rocks (Sanford and Grant, 1990;Reed and others, 2004) as well as hidden beneath the lower St. Lawrence River, Honguedo Strait and the Gulf of St. Lawrence. Until Silurian left-lateral faults are identified, however, the pull-apart basin hypothesis is speculative.…”

Section: Cause Of Extensionmentioning

confidence: 98%

Silurian extension in the Upper Connecticut Valley, United States and the origin of middle Paleozoic basins in the Québec embayment

Rankin¹,

Coish²,

Tucker³

et al. 2007

Am J Sci

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Pre-Silurian strata of the Bronson Hill arch (BHA) in the Upper Connecticut Valley, NH-VT are host to the latest Ludlow Comerford Intrusive Suite consisting, east to west, of a mafic dike swarm with sheeted dikes, and an intrusive complex. The rocks are mostly mafic but with compositions ranging from gabbro to leucocratic tonalite. The suite is truncated on the west by the Monroe fault, a late Acadian thrust that carries rocks of the BHA westward over Silurian-Devonian strata of the Connecticut Valley-Gaspé trough (CVGT). Dikes intrude folded strata with a pre-intrusion metamorphic fabric (Taconian?) but they experienced Acadian deformation.Twenty fractions of zircon and baddeleyite from three sample sites of gabbrodiorite spanning nearly 40 km yield a weighted 207 Pb/ 206 Pb age of 419 ؎ 1 Ma. Greenschist-facies dikes, sampled over a strike distance of 35 km, were tholeiitic basalts formed by partial melting of asthenospheric mantle, with little or no influence from mantle or crustal lithosphere. The dike chemistry is similar to mid-ocean ridge, within-plate, and back-arc basin basalts. Parent magmas originated in the asthenosphere and were erupted through severely thinned lithosphere adjacent to the CVGT. Extensive middle Paleozoic basins in the internides of the Appalachian orogen are restricted to the Québec embayment of the Laurentian rifted margin, and include the CVGT and the Central Maine trough (CMT), separated from the BHA by a Silurian tectonic hinge. The NE-trending Comerford intrusions parallel the CVGT, CMT, and the tectonic hinge, and indicate NW-SE extension. During post-Taconian convergence, the irregular margins of composite Laurentia and Avalon permitted continued collision in Newfoundland (St. Lawrence promontory) and coeval extension in the Québec embayment. Extension may be related to hinge retreat of the northwest directedBrunswick subduction complex and rise of the asthenosphere following slab break-off. An alternative hypothesis is that the basins originated as pull-apart basins between northwest-trending, left-stepping, sinistral strike-slip faults along the southern flanks of the New York and St. Lawrence promontories.

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Bedrock geological mapping and basin studies in the Gulf of St. Lawrence

Cited by 21 publications

References 0 publications

Surface and subsurface signatures of gas seepage in the St. Lawrence Estuary (Canada): Significance to hydrocarbon exploration

Surface and subsurface signatures of gas seepage in the St. Lawrence Estuary (Canada): Significance to hydrocarbon exploration

Lower Paleozoic configuration of the Quebec reentrant based on improved along-strike paleogeography

Silurian extension in the Upper Connecticut Valley, United States and the origin of middle Paleozoic basins in the Québec embayment

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