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TitreTemperature measurements and thermal gradient estimates on the slope and shelf-edge region of the Beaufort Sea, Canada
TéléchargerTéléchargements
AuteurRiedel, M; Villinger, H; Asshoff, K; Kaul, N; Dallimore, S R
SourceCommission géologique du Canada, Dossier public 7725, 2015, 143 pages, https://doi.org/10.4095/296570
Année2015
ÉditeurRessources naturelles Canada
Documentdossier public
Lang.anglais
DOIhttps://doi.org/10.4095/296570
Medianumérique; en ligne
Formatspdf
ProvinceRégion extracotière du nord
Lat/Long OENS-138.0000 -134.0000 70.9667 69.9167
Sujetslevés géophysiques; sismographes; réseau sismique; séismologie; ondes sismiques; levés acoustiques; levés acoustiques marins; bathymétrie; plate-forme continentale; talus continental; dépôts de pentes; temperature; gradient géothermique; températures géothermiques; pergélisol; glace fossile; géophysique; combustibles fossiles
Illustrationslocation maps; tables; photographs; profiles; plots; images; screen captures
Consultation
Endroit
 
Bibliothèque de Ressources naturelles Canada - Ottawa (Sciences de la Terre)
 
ProgrammeRisques géo marines, Géoscience pour la sécurité publique
Diffusé2015 05 29
Résumé(disponible en anglais seulement)
In situ temperature measurements were conducted at 63 gravity-core stations during the 2013 expedition with the CCGS Sir Wilfrid Laurier in the Canadian Beaufort Sea. Outriggers attached to the outside of the gravity core-barrel were used to mount portable miniature temperature loggers (MTL) for down-core in situ temperature measurements. Several sub-regions were investigated during the expedition including two shelf-slope crossings, three mud volcano-type expulsion features, as well as two canyon sites. The last site visited was at the Gary Knolls, just east of the Mackenzie Trough at water depths of less than 100 m. Overall, temperature data obtained from the MTLs were of high quality at most stations and the data acquisition technique was proven to be robust and easy to adapt in the Arctic. However, depth determination for each logger position remains the largest challenge as no additional pressure sensor was used with the MTLs. Instead, depths were estimated based on the apparent core penetration and the geometry of the outriggers. The most significant result from this work is the discovery of the very large apparent geothermal gradients associated with the two expulsion features (EF) Coke Cap and the mud volcano at 420 m water depth. Temperatures measured within the top 2.5 meter below seafloor suggest geothermal gradients of up to 2.94ºC/m (Station 96, 420m EF) and 1.37 ºC/m (Station 58, Coke Cap EF). Away from the centre of the EFs, thermal gradients decrease to values of 0.5ºC/m for Station 99 at the 420 m EF, and 0.92ºC/m at Station 21 at the Coke Cap EF. Temperature data across the slope-shelf transect and the two transects across the canyon heads did not reveal considerable geothermal gradients, but show a water-depth dependent trend in temperature. From deep to shallow water, temperature appear to decrease until the most negative temperature values are found on the shelf itself at water depths of ~100 m (-1.2 to -1.4ºC). Overall, data from the top 1.0 to 1.5 meter below seafloor are likely affected by seasonal variations in the water column temperature and may not be used to define geothermal gradients. With an optimal full penetration of the core barrel, the deepest temperature data are from ~2.3 mbsf, which limits the accuracy of the estimated geothermal gradients as only few data points (2 - 4) can be used in the calculations.
Résumé(Résumé en langage clair et simple, non publié)
Lors de l'expédition de 2013 menée à bord du NGCC Sir Wilfrid Laurier dans la partie canadienne de la mer de Beaufort, des mesures de température ont été prises dans 63 stations. Des tangons attachés à l'extérieur d'un tube de carottage par gravité ont servi à installer des enregistreurs de température miniatures et portatifs. On a étudié plusieurs sous-régions dont deux traversées du plateau-talus, trois reliefs d'expulsion de volcan de boue ainsi que deux canyons. Le dernier site visité était aux monticules Gary, à l'est de la dépression du Mackenzie. Les données sur la température fournies par les enregistreurs de température miniatures étaient de grande qualité. Le résultat le plus remarquable est la présence de très importants gradients géothermiques associés à deux reliefs d'expulsion, soit le « Coke Cap » et le volcan de boue à 420 m de profondeur. Les données suggèrent des gradients géothermiques atteignant 2,94 °C/m (Station no 96, relief d'expulsion à 420 m) et 1,37 °C/m (Station no 58, relief d'expulsion « Coke cap »).
GEOSCAN ID296570