ACCRETE MCS data synthesis reflects tectonic history of the northern continental margin of British Columbia

Diebold, J B (1), Hollister, L S (2); Das, T (1)

(1)Lamont-Doherty Earth Observatory, PO Box 8000 Palisades, NY 10964 United States; (2) Department of Geosciences, Princeton University Princeton, NJ 08544 United States

Abstract:
We present interpretations of 500 km of multichannel seismic reflection data acquired in Southeast Alaska as part of the ongoing ACCRETE project. These data allow the offshore extrapolation of structures mapped onshore (e.g. Chardon, et al., this session) and of structures inferred from plate tectonic reconstructions. Marked changes in crustal reflectivity appear to correlate with the offshore extension of the Alexander-Wrangellia terrane boundary,previously inferred to cross Dixon Entrance. The pronounced linear geologic feature in SE Alaska and British Colombia, called the Coast Shear Zone [CSZ], is seen to coincide with a change in crustal thickness, and a pronounced contrast in the patterns of crustal reflections. Broad Moho arches on both sides of the CSZ appear to have resulted during the most recent [10 - 20 Ma] transtensional regime.

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