CRUSTAL STRUCTURE OF THE NOVA SCOTIA MARGIN

The Nova Scotia margin is located at a transition from volcanic margins in the south to non-volcanic margins in the north along the Eastern Atlantic continental margin system. South of the Nova Scotia margin, seaward dipping reflections (SDR) and a high-velocity lower crustal layer are observed across the ocean-continent transition (OCT), indicative of volcanic margins. North of the Nova Scotia margin, no SDR is observed and thin crust overlies serpentinized mantle across the OCT. Along the Nova Scotia margin, an SDR sequence is observed but only on the southern-most part neighboring Georges Bank. The East Coast Magnetic Anomaly, possibly related to an igneous wedge, extends further to the north but disappears south of the Scotian Basin.

In order to understand the crustal structure of this transition from volcanic to non-volcanic margin, three wide-angle seismic reflection/refraction (WAR/R) profiles were acquired across the full width of the Nova Scotia margin in 2001, to delineate the crustal features from continental crust to oceanic crust. The northern profile crosses the Scotian Basin and coincides with existing multi-channel seismic reflection (MCS) profile 89-1; the middle profile crosses the Lahave Platform and coincides with MCS profiles 88-1 and 88-1a; the southern profile crosses the southwestern part of the margin. Results show that the northern part of this margin is non-volcanic, with serpentinized mantle below the OCT and thin oceanic crust seaward, which is 4 km thick. Along the middle WAR/R profile, preliminary results indicate that serpentinized mantle is also observed below the OCT, but the oceanic crust is 1-2 km thicker than that of the northern profile. This indicates increasing volcanism from the northern part of this margin to the south part of this margin. A full comparison of the models along the middle and northern profiles will be presented at the meeting.