NW-oriented features on both sides of the Atlantic Ocean: evidence for a Paleozoic collision that formed the Labrador-Biscay wrench fault zone?

Abstract

Northwest-oriented features have been recognized for many years as fundamental components of the geology of the northwestern European continental shelves. Similarly oriented lineations and faults have been mapped throughout southwestern Britain, western France and across the English Channel. On land in Europe, similar trends are identified as far east as the Urals. Features of similar orientation, extending over a broad area on the North American continental shelf, have recently been identified from geophysical trends. On land in eastern Canada NW-SE faults have been mapped geologically and detected using geophysical and remote sensing data. A Mercator projection map on which the Atlantic Ocean has been restored to its pre-Mesozoic configuration, i.e. before the initiation of the most recent opening of the North Atlantic Ocean, shows that the features are similarly oriented. Although some of the trends showing this direction may be younger, the geological data from both sides of the Atlantic Ocean suggest that the event that led to the formation of these NW-SE features postdated the Variscan orogeny and may have been associated with the collision between Gondwana and Laurasia. The geometric patterns of the features interpreted as associated with the collision are consistent with patterns produced by a simple physical sandbox model of indentation with a rigid confinement to the west and a small lateral confinement to the east. This configuration is similar to that expected of Gondwana and Laurasia during the late Paleozoic. Faults considered younger than this collision may represent tectonic rejuvenations associated with the initiation of the opening of the North Atlantic Ocean. L'orientation observde du nord-est vers le sud-est des formations rocheuses est reconnue depuis de nombreuses ann6es comme une caractdristique gdologique fondamentale des plateaux continentaux du nord-ouest de l'Europe. Des structures lindaires et des failles d'orientation similaires ont 6t6 repertories dans tout le sud-ouest de FAngleterre, dans l'ouest de la France et k travers la Manche. Sur le continent europden, des tendances analogues ont pu etre observdes aussi loin k Test que dans la chaine de l'Oural. Ces caractdristiques orientdes qui recouvrent une vaste rdgion du plateau continental de l'Amdrique du Nord ont rdcemment dtd observdes a partir de tendances gdophysiques. Dans l'Est canadien, des failles orientdes NOSE ont dtd portdes sur des cartes gdologiques et ddtectdes k l'aid.e de donndes gdophysiques et de tdldddtection. Ces caractdristiques observdes ont dtd portdes sur une carte k projection de Mercator ou figure l'ocdan Atlantique dans sa configuration d'origine pendant l'dre prd-mdsozo'fque, soit avant que ne s'amorce l'ouverture la plus rdcente de l'Atlantique Nord. Ces caractdristiques reproduisent la meme orientation lorsqu'elles sont portdes ainsi sur la carte. Bien que certaines des tendances qui signalent cette orientation semblent d'apparition plus rdcente, les donndes gdologiques des deux cotds de l'Atlantique por...

Geology and Hydrogeology of Faults on Cape Breton Island, Nova Scotia, Canada: an overview

“…3) along the edges of the Carboniferous basins (Gibling et al 1987) formed initially as strike-slip faults, later re-activated as normal faults. Lefort and Miller (1999) suggested that the strong northwest-oriented, megalineaments present over the island could be related to wrench faulting formed during the collision between Gondwana and Laurasia in the late Paleozoic, during the closure of the remaining oceanic tract between the two continents.…”

“…This rifting resulted in reactivation of the CobequidChedabucto and Hollow Fault-Aspy Fault systems, as well as reactivation of basin-bounding strike-slip faults as normal faults (Faure et al 2006;Herman 2009). Lefort and Miller (1999) suggested that the northwest-to westoriented wrench faults created pre-existing basement weaknesses, which were reactivated during Mesozoic rifting.…”

“…Thomas (2014) noted a similar trend in transform faults formed during the initial rifting at the Iapetan margin of Laurentia. Both Thomas (2014) and Lefort and Miller (1999) concluded that these faults formed zones of weakness which were subsequently reactivated during rifting in the Mesozoic and Cenozoic with formation of the Atlantic Ocean. The concept was also supported by Thomas (2006) who concluded that these structures were related to transform faults and along with aligned compressional structures show repeated tectonic inheritance through successive Wilson cycles of supercontinent assembly and breakup.…”

“…However, in many places, regional bedrock geological mapping has not identified faults associated with these features. Using geophysical data, Lefort and Miller (1999) mapped northwest-and west-oriented faults and lineaments on both sides of the Atlantic rift throughout western Europe (supported by Dore et al 1997) and eastern Canada. They suggested that the features were initially formed as a result of northwest-oriented wrench zones located close to the initial Gondwana and Laurasia collision front in the late Paleozoic.…”