Sedimentary basins and basement highs beneath the polar shelf north of Axel Heiberg and Meighen islands

摘要

A seismic refraction program was carried out on the northeastern polar continental shelf north of Axel Heiberg and Meighen islands. Five distinct velocity units were identified throughout the area. The deepest unit, velocity unit 1, has velocities of 8.2 km/sec and represents the ultramafic, uppermost mantle. The top of this unit is the MOHO and it is about 25 km deep on the inner shelf and rises to 20 km on the outer shelf. The next velocity unit (2) has velocities of 6.6 to 6.8 km/sec and correlates well with the crystalline lower crust. Velocity unit 3 is characterized by velocities of 5.9 to 6.2 km/sec and is interpreted to consist primarily of highly indurated clastic and carbonate strata, volcanics and intrusives of the highly deformed, late Proterozoic to early Paleozoic Franklinian Basin. Along the shelf edge this unit may also encompass Lower Cretaceous volcanic flows and Jurassic-Cretaceous strata which are extensively intruded by sills and dykes. The top of this unit is considered to be "basement". Velocity unit 4 has velocities between 4.3 and 5.3 km/sec and is interpreted to consist mainly of mid Jurassic to Paleogene deltaic to basinal clastic strata. This unit is up to 10 km thick and occurs throughout the study area except over an offshore extension of the Princess Margaret Arch on the inner shelfand the crest of a prominent shelf edge high. The strata encompassed by this unit are likely deformed by folds and faults generated during the early Tertiary Eurekan Orogeny. Velocity unit 5 has velocities of 1.9 to 3.4 km/sec and probably comprises the undeformed Neogene succession. This unit is a few kilometres thick over much of the shelf and may include buried Upper Cretaceous-Paleogene strata on the inner shelf. The potential of the deformed Cretaceous-Paleogene succession to contain hydrocarbons is high but the presence of the Arctic ice pack over the area hampers traditional exploration.%Une programme de sismique réfraction a été conduit sur le plateau continental polaire au nord des îles d'Axel Heiberg et de Meighen. Cinq unités de vélocité distinctes ont été identifiées à travers la région. L'unité la plus profonde, ou unité de vélocité 1, a une vélocité de 8,2 km/s et représente le manteau supérieur, ultramafique. Le sommet de cette unité est le MOHO et est situé à près de 25 km de profondeur sur le plateau intérieur et monte jusqu'à à 20 km sur le plateau extérieur. L'unité de vélocité suivante (2) montre des vélocités allant de 6,6 à 6,8 km/s et se corrèle bien avec la croûte cristalline inférieure.