Crustal Structure of the Central Nova Scotia Margin from Seismic Refraction Data: New Evidence for Non-volcanic Rifting

Details Crustal Structure of the Central Nova Scotia Margin from Seismic Refraction Data: New Evidence for Non-volcanic Rifting Crustal Structure of the Central Nova Scotia Margin from Seismic Refraction Data: New Evidence for Non-volcanic Rifting

May 2004

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004agusm.t41b..07w&link_type=abstract

American Geophysical Union, Spring Meeting 2004, abstract #T41B-07

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3025 Marine Seismics (0935), 8105 Continental Margins And Sedimentary Basins

Scientific paper

The Nova Scotia margin off Eastern Canada is located at a transition from volcanic margins in the south to non-volcanic margins in the north. The southern Nova Scotia margin is largely volcanic, evidenced by seaward dipping reflections (SDR) coinciding with a strong East Coast Magnetic Anomaly (ECMA). The northern part of the margin shows no evidence of major volcanism where the ECMA weakens and eventually disappears. In the central part of the margin, no SDRs have been observed but the ECMA is still prominent. This raises doubt about where the transition from a volcanic to a non-volcanic style margin exactly occurs. In order to study this transition, three wide-angle refraction lines were acquired in 2001 across the northern, central and southern parts of the margin, respectively. The middle line extends from the Lahave Platform into the Sohm Abysmal Plain. The velocity model derived from the refraction data shows no evidence for a magmatic underplated layer beneath the continental crust, suggesting non-volcanic rifting. In addition, a 120-km wide region of partially serpentinized mantle is observed within the ocean-continent transition zone, similar to other non-volcanic margins in the North Atlantic. Together, these observations are difficult to reconcile with significant volcanism, and the ECMA with reduced amplitude in this region is not likely to be related to volcanic activity as it is farther to the south. The velocity model also shows that the continental crust is thinned during rifting initially within the middle and lower crust beneath the hinge zone, and subsequently within the upper crust. The thinned upper continental crust extends over a distance of 180 km up to a highly faulted basement structure; the continent-ocean boundary is then located some 60 km farther seaward than an earlier interpretation by Keen et al. (1991) based only on reflection seismic data. Keen C. E., MacLean B. C. & Kay W. A., 1991. A deep seismic reflection profile across Nova Scotia continental margin, offshore eastern Canada. Can. J. Earth Sci., 28, 1112-1120.

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