bedford institute of oceanography 2001 in review - Région des ...

SCIENCE ACTIVITIES / Geological Survey of Canada (Atlantic)The red line is the cruise track, totaling 6400 km, between Ellesmere Island in thewest and Greenland to the east. Seismic data, bathymetric measurements, watersamples, and temperature profiles were collected along these lines. In the backgroundis the coast of Greenland south of 78 0 N.the Arctic ecosystem. The water samples and temperature profilescollected are also useful for monitoring short-term climate change.Sediment cores and grab samples were collected by GSC to study thepost-ice age evolution of the region. These data are required for understandinglong-term variability in the Earth’s climate. Because of thesensitivity of Arctic habitats, a marine mammal scientist was includedin the expedition to observe ice and weather conditions, distributionof wildlife, and provide a critical evaluation of the environmentalimpact posed by the scientific activities.Aeromagnetic data were acquired by towing a sensor from a helicopter.This style of surveying allows for direct correlation betweenonshore and offshore magnetic anomalies. A total of 9000 km ofaeromagnetic data were collected. In the northern part of NaresStrait, the magnetic anomaly map shows prominent northeasttrending linear features. Based on the onshore geological studies,these anomalies are coincident with sedimentary rocks having unusuallyhigh concentration of magnetic particles. Without the onshoremapping, these anomalies might have been interpreted as caused byigneous rocks. The existence of offshore sedimentary basins is alsointeresting because the regional geology indicates that there are bothsource and reservoir rocks for hydrocarbons. The fission trackstudies, to be performed in 2002 and beyond, as part of this program,will indicate if the thermal maturity of the basins is appropriate foroil and gas generation.The major geophysical component of the cruise was the acquisitionof three types of seismic data: 1) high resolution reflection for imaging100 m below the seafloor, 2) multichannel reflection for penetration to5 km, and 3) refraction to map large-scale structures from 0-40 km indepth. The ship’s bubbler system, used for assisting with difficult iceconditions, proved an asset for towing seismic equipment behind theship in ice infested waters. The bubbles moved the ice away from thestern, providing an ice-free zone behind the ship.The cliffs at Cape Lawrence (shown below), on Ellesmere Islandare formed by thrusting. The narrow bands of red rocks are about 600million years old. In contrast, the cliff face on the right, with the icefreewater in front of it, is 60 million years old. The seismic profileshows strata that are gently warped toward the surface. The interpretedseismic section reveals a basin formed in the space before thefrontal thrust along the coast. This is equivalent to the structures youThe aeromagnetic survey covering a portion of northern Nares Strait and onshoreEllesmere Island.The upper section is a photo of a thrust on the coast of Ellesmere Island near 80 0 N.It also illustrates the ice conditions encountered in Nares Strait. The open water areawas enlarged by the ship before the seismic gear was streamed. The lower half is aportion of the seismic reflection profile collected perpendicular to the photo.14 / BIO-2001 IN REVIEW