Geophysical characteristics of the continental crust along the Lithoprobe Eastern Canadian Shield Onshore–Offshore Transect (ECSOOT): a review

Abstract

The Eastern Canadian Shield Onshore–Offshore Transect (ECSOOT) of the Lithoprobe program included 1200 km of normal-incidence seismic profiles and seven wide-angle seismic profiles across Archean and Proterozoic rocks of Labrador, northern Quebec, and the surrounding marine areas. Archean crust is 33–44 km thick. P-wave velocity increases downwards from 6.0 to 6.9 km/s. There is moderate crustal reflectivity, but the reflection Moho is unclear. Archean crust that stabilized in the Proterozoic is similar except for greater reflectivity and a well-defined Moho. Proterozoic crust has similar or greater thickness, variable lower crustal velocities, and strong crustal reflectivity. Geodynamic processes of Paleoproterozoic growth of the Canadian Shield are similar to those observed in modern collisional orogens. The suturing of the Archean Core Zone and Superior provinces involved whole-crustal shearing (top to west) in the Core Zone, linked to thin-skinned deformation in the New Quebec Orogen. The Torngat Orogen sutures the Nain Province to the Core Zone and reveals a crustal root, in which Moho descends to 55 km. It formed by transpression and survived because of the lack of postorogenic heating. Accretion of the Makkovik Province to the Nain Province involves delamination at the Moho and distributed strain in the juvenile arcs. Delamination within the lower crust characterizes the accretion of Labradorian crust in the southeastern Grenville Province. Thinning of the crust northwards across the Grenville Front is accentuated by Mesozoic extension that reactivates Proterozoic shear zones. The intrusion of the Mesoproterozoic Nain Plutonic Suite is attributed to a mantle plume ponding at the base of the crust.

Correlation of Archaean and Palaeoproterozoic units between northeastern Canada and western Greenland: constraining the pre-collisional upper plate accretionary history of the Trans-Hudson orogen

“…The apparent eastward widening of the Makkovik orogen continues offshore, as documented by data from offshore wells and seismic lines (Kerr et al 1996Wasteneys et al 1996;Hall et al 2002). Overall, the belt records c. 300-600 Ma of convergent continental margin activity, including the accretion of several arc and back-arc units, as well as possibly a small Archaean terrane, punctuated by evidence of intra-accretion quiescent periods (Gower et al 1990;Kerr 1994;Kerr et al 1997;Culshaw et al 2000b;Ketchum et al 2001aKetchum et al , b, 2002.…”

The southeastern Churchill Province: synthesis of a Paleoproterozoic transpressional orogen

“…7) that was interpreted by Hall et al (1995) as the core zoneTasiuyak domain boundary. Some west-dipping reflectors have also been noted (Hall et al 2002), but their origin is unclear.…”

“…The best normal-incidence reflection data were collected from this western part of the line and indicate a number of shallow, east-dipping to flat reflectors penetrating to the reflection Moho. These have been interpreted by Hall et al (2002) Fig. 2.…”

Tectonostratigraphic evolution of the Labrador margin, Atlantic Canada

“…Both margin offsets are associated with inverted structures (black circles) on the shelf. These offsets project to large-scale geologic features on land: the Grenville Front and major fault zones (FZ; Hall et al, 2002). The location of the North Bjarni F-06 and Bjarni H-81 gas fields, which contain 3.1 TCF, is shown by the black dot.…”

“…Magnetic anomalies (chrons) 31, 27, 25, 24 and 21 are labeled. Onshore geologic features are from Hall et al (2002). possibility that there are world-class, Kimmeridgian source rocks on the Labrador margin. Jurassic carbonatites in southwest Greenland, indicate an increase in extensional stress during this interval (ca.…”