A new seismic model of Canada's northeasternmost margin indicates a complex continent to ocean transition with similarities to both volcanic and nonvolcanic margins. The crustal structure beneath the Lincoln Sea includes: (i) a continental shelf with a uniform 3 km thick cover (velocity = 1.8-3.6 h i s ) overlying at least 6 km of synrift(?) basinal strata (velocity = 4.3-4.9 M s ) that terminate near the base of the slope; (ii) a thick unit of oceanic layer 2-type. velocity (5.4-5.8 h i s ) overlying a velocity structure resembling a volcanic margin; (iii) a high-velocity lower crust (> 7.4 kmls) resembling North Atlantic volcanic margins or the Alpha Ridge but different from the Lomonosov Ridge near the North Pole; (iv) a change in velocity structure 15-25 km seaward of the shelf-slope break that coincides with a distinct short-wavelength, highamplitude magnetic anomaly and the centre of a steep gravity gradient; and (v) a suggested Moho depth of 23 km beneath the Lincoln Sea margin along 63 O W .The velocity structure beneath the Lincoln Sea is transitional from thinned continental crust beneath the shelf to a structure with oceanic affinities to the north. Typical, 10 km thick oceanic crust is not apparent beneath the northern Lincoln Sea. The upper crustal structure resembles a rifted, nonvolcanic margin such as the Goban Spur, while the high lower crustal velocity resembles a volcanic margin like the Hatton Bank or an oceanic complex like the Alpha Ridge. North of the seismic survey, the enigmatic Lincoln Sea plateau may be an intruded Lomonosov Ridge segment or a volcanic complex similar to the Alpha Ridge or the Morris Jesup Plateau.Un modtle sismique nouvellement dabor6 pour la marge de 11extr6mit6 nord-est du Canada indique une transition continentale 21 ochnique complexe, prtsentant des traits cornrnuns aux marges volcaniques et non volcaniques. La structure crustale sous la mer de Lincoln inclut : (i) une plate-forme continentale avec une couverture uniforme d'une 6paisseur de 3 km (vitesse = 1,8-3,6 M s ) , qui recouvre au moins 6 km de strates d6pos6es dans un bassin en distension(?) (vitesse = 4,3 -4,9 h i s ) disparaissant p r b de la base du talus; (ii) une unit6 form6e d'une puissante couche oc6anique de vitesses de type-2 (5,4-5,8 h i s ) , sus-jacente B une structure de vitesses ressemblant B une marge volcanique; (iii) une crofite inf6-rieure de vitesses 6lev6es (>7,4 kmls) semblable aux marges volcaniques de 1'Atlantique Nord ou B la crgte d'Alpha, mais qui differe de la crgte de Lomonosov prts du p61e Nord; (iv) un changement dans la structure de vitesses B 15 -25 km vers le large de la discontinuit6 entre la plate-forme et le talus, coincidant avec une anomalie magnCtique de forte amplitude et de longueur d'onde courte distincte et avec le centre d'un gradient gravitaire abrupt; et (v) une profondeur sugg6r6e de 23 krn pour le Moho sous la marge de la mer de Lincoln, le long du 63" de longitude ouest.La structure de vitessses sous la mer de Lincoln indique le passage graduel d'une crofite ...

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Finding efficient and accurate ways to map and monitor methane sources is becoming a priority within government and industry, both for environmental applications and hydrocarbon exploration. For more than 10 years, Sander Geophysics and Shell have cooperated to develop airborne methods to detect and measure the enhanced methane concentrations associated with ground-level sources. The resulting data can be processed using a Markov chain Monte Carlo method (MCMC) to determine the locations and emission rates of the methane sources responsible. SGMethane is the name of Sander Geophysics' methane survey method, resulting from the collaboration with Shell. It consists of an optical gas sensor, an anemometer, a GPS, and an inertial navigation system, analogous to Shell's LightTouch method. A test survey was flown over two active waste landfill sites close to Ottawa, Ontario, Canada, and the modeled data corroborated the locations of the dumpsites. Several commercial surveys for environmental monitoring and hydrocarbon exploration have been flown in a wide variety of different countries and climates; these show that both systems can detect localized anomalous methane sources even in the presence of dense vegetation, such as a tropical rainforest.

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