GEOSCAN, résultats de la recherche


TitreInitial results from new normal incidence seismic reflection data over Canada Basin
AuteurHutchinson, D; Shimeld, J; Wade, J; Jackson, R; Chian, D; Harrison, C
SourceTectonic development of the Amerasia Basin, Geological Society of America, Penrose Conference abstracts volume; 2009.
Séries alt.Secteur des sciences de la Terre, Contribution externe 20090137
RéunionGeological Society of America, Penrose Conference; Banff; CA; Octobre 4-9, 2009
ProvinceRégion extracotière du nord
Sujetslevés de reflexion sismiques; levés géophysiques; topographie du fond océanique; topographie du fond océanique; bathymétrie; levés sismiques marins; levés acoustiques marins; géophysique; géologie marine
ProgrammePreparation of a submission for an extended continental shelf in the Atlantic and Arctic Oceans under UNCLOS, Délimitation du plateau continental du Canada en vertu de la Convention des Nations Unies sur le droit de la mer (UNCLOS)
Résumé(disponible en anglais seulement)
Approximately 5800 km of high-quality multichannel seismic reflection data were collected in the Canada Basin of the Arctic Ocean during the first two years of an on-going four year collaboration between the Geological Survey of Canada (GSC) and the U.S. Geological Survey. The 16-channel data were acquired using an ice-strengthened system designed by the GSC and operated from Canadian Coast Guard Ship Louis S. St-Laurent. U.S. Coast Guard Cutter Healy assisted in the acquisition during 2008 by breaking a path through the ice ahead of Louis in the most northern and eastern lines of the survey, where the ice was thickest.
Preliminary analysis of the data shows that basement is imaged on all but the southeastern portion of Canada Basin where the first seafloor multiple obscures the deepest reflections. Sediment thicknesses, as measured between the sea floor and acoustic basement, range from zero near the Alpha Ridge to more than 4.1 sec two-way travel time in parts of the central and eastern basin. Seismic stratigraphic interpretation yields about a dozen horizons that can be mapped regionally to define prerift, synrift, and postrift packages. Correlation of seismic horizons is tentative until additional coverage provides tie lines. Except for the southeastern portion of the survey, the entire sedimentary succession shows remarkably little disturbance since deposition. Although faulting occurs within the sequences, stratigraphic offsets are minor, and faults that extend from basement through the entire sedimentary sequence are rare. The escarpment along Northwind Ridge appears to be an onlap surface that has been tectonically quiet since deposition of the oldest strata. On the continental margin near Banks Island of the Canadian Beaufort Sea, an area of folding that becomes more intense in a shoreward direction occurs in the sedimentary package and may indicate either contractional tectonics or gravitational sliding. Throughout the deep-water parts of the basin, large mass transport deposits are imaged in the upper half of the sedimentary section.
The new multichannel data provide 6 crossings of the 1000-km long by 50-km wide curvilinear central Canada Basin gravity low, which has been previously attributed to a seafloor spreading center. These new data reveal that the gravity low actually marks a fundamental boundary separating distinct and asymmetric sedimentary and basement styles. Directly beneath the gravity anomaly is a narrow, symmetrical graben containing some of the oldest horizons in the basin. West of the anomaly, near Northwind Ridge, generally thinner sediments overlie a smooth basement that dips towards the graben. On the east, sediments are thicker and basement is rough, faulted, and deeper. While these new data are consistent with extension, particularly extension focused in grabens, they preclude a typical spreading center along this negative gravity anomaly.