Data Figures

New Multichannel seismic resutlts. Multichannel seismic [MCS] reflection profiles, acquired in Dixon Entrance by R/V EWING in 1994 as part of the ACCRETE project, imaged crustal reflectors and Moho across the fundamental pair of structural boundaries separating the Alexander, Wrangellia, and North America terranes. The eastern margin of the Alexander terrane features strong crustal reflectors, mostly dipping gently (ca. 12 degrees) WSW. Moho reflections within this zone are stronger and more continuous than those seen in the terranes to the east. A broad Moho arch, about 3 km high, 100 km wide, and striking NNE, is defined by two E-W profiles, 45 km apart. These two profiles are tied by a third, arch-parallel line. Minimum Moho two-way time is 8 seconds, corresponding to a Moho depth of approximately 26 km. It is likely that this crustal arching is the result of the Tertiary extension forming Queen Charlotte Basin. The overall strike of the arch is oblique to nearby terrane boundaries, to graben and half-graben structures previously mapped in Dixon Entrance and Hecate Strait, and to the trend of Queen Charlotte Basin, which lies to the south. The zone of thin crust defined by this Moho arch is apparently discontinuous with similar zones mapped in Hecate Strait and Queen Charlotte Basin, suggestiong their creation by oblique extension (transtension).
Figure 2. See discussion first abstract under "SNORCLE '97" button.

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