GEOSCAN, résultats de la recherche


TitreExtent of oceanic crust in the Labrador Sea
AuteurSrivastava, S P; Roest, W R
SourceMarine and Petroleum Geology vol. 16, issue 1, 1999 p. 65-84,
Séries alt.Commission géologique du Canada, Contributions aux publications extérieures 1997179
ÉditeurElsevier BV
Documentpublication en série
Mediapapier; en ligne; numérique
ProvinceRégion extracotière de l'est
Lat/Long OENS -62.0000 -46.0000 64.0000 55.0000
Sujetsfailles en bloc; croûte continentale; failles; expansion océanique; anomalies gravimétriques; anomalies magnétiques; croûte océanique; données sismiques; tectonique; géologie structurale
Illustrationslocation maps; geological sketch maps; tables; graphs; gravity profiles; seismic reflection profiles
Résumé(disponible en anglais seulement)
This paper examines the mode of formation of the northern margins of the Labrador Sea. Observations of faulted and rotated crustal blocks across the northwest margin of Greenland had led to the suggestion that this region is underlain by extended continental crust. A detailed analysis of all geophysical data from this region, presented here, suggests, on the contrary, the possibility that it could have been formed by an excessively slow seafloor spreading process, and ridge axis propagation. This gave rise to rotated fault blocks at a time when spreading was mainly confined to the Greenland side prior to its shift to the west. Supporting evidence for such a reconfiguration of the spreading axis comes from gravity and magnetic observations of this and neighbouring regions. Modelling of magnetic anomalies in the area, based on the average rate of spreading for the entire Labrador Sea, shows that a gradual shift of the ridge axis to the west started after the formation of anomaly 32. Because the earliest seafloor spreading anomalies are highly attenuated in amplitudes, other models like extended and intruded continental crust are possible if one only considers the magnetic anomalies. However, an extended continental crustal model poses problems in accounting for other geophysical observations. Based on a slow spreading model it is shown that oceanic crust extends fairly close to the foot of the slope, with a narrow belt of extended continental crust along the west Greenland margin while a much wider zone of perhaps attenuated continental crust extends off Labrador. Breakup of the continental landmass occurred much closer to the west Greenland coast than to Labrador. The applicability of a slow spreading model to other passive margins, where similar geophysical observations have been reported, is discussed.