Analysis and interpretation of standard MCS (streamer length <~6 km) and OBS (20-40 km instrument spacing) profiles collected offshore Nova Scotia shows a first-order margin parallel change in rifting architecture, from the magma-rich U.S. East Coast margins in the south to the magma-poor Grand Bank/Newfoundland margin in the north. While these data and work were critical for characterizing the largest regional scale structure, more detailed information on the continent-ocean transition anywhere offshore Nova Scotia was lacking. To start filling in this gap, in 2009, a modern dense wide-angle profile OETR (Figure 1) was acquired across the northeastern Nova Scotia margin for the Offshore Energy Research Association by GeoPro GmbH. The much smaller OBS spacing on this profile than on the SMART profiles and the high definition of the crystalline basement available from the coincident long-streamer GXT-2000 MCS line allows for extraction of detailed crustal structural information.
The OETR wide-angle seismic data were acquired along the 405-km-long profile located ~100 km to the east of the wide-angle seismic profile SMART-1 (Figure 1). Data useful for analysis were recorded on 78 out of the 100 deployed OBSs, all with a sampling interval of 4 ms. Instrument spacing ranges from <3 km across the presumed continent-ocean transition to ~10 km at the seaward end of the profile, and ~5 km for the remaining sections of the profile. Within each OBS, a group of three 4.5-Hz geophones (two horizontal and one vertical component) were mounted at the bottom of a glass sphere, which also housed the seismic recording unit. An external hydrophone was mounted to the top of the sphere. An array of eight airguns (total volume of 64 L), towed at 10-m depth, was fired every 60 s to provide an average shot spacing of ~124 m. Only the vertical geophone and hydrophone data were analyzed (Lau et al., 2018) so far. The results show a >4-km-thick serpentinized mantle layer beneath thin crust within the continent-ocean transition that indicates limited melt supply during rifting. Synrift extension was amagmatic on both conjugate margins but with asymmetry resulting from postrift volcanism on the Moroccan margin.