Wrangellia flood basalts in Alaska, Yukon, and British Columbia : exploring the growth and magmatic history of late Triassic oceanic plateau ...

• Main Author: Greene, Andrew R.
• Format: Text
• Language: English
• Published: University of British Columbia 2008
• Subjects: Yukon; Alaska
• Online Access: https://dx.doi.org/10.14288/1.0052552; https://doi.library.ubc.ca/10.14288/1.0052552

The Wrangellia flood basalts are parts of an oceanic plateau that formed in the eastern Panthalassic Ocean (ca. 230-225 Ma). The volcanic stratigraphy presently extends >2300 km in British Columbia, Yukon, and Alaska. The field relationships, age, and geochemistry have been examined to provide constraints on the construction of oceanic plateaus, duration of volcanism, source of magmas, and the conditions of melting and magmatic evolution for the volcanic stratigraphy. Wrangellia basalts on Vancouver Island (Karmutsen Formation) form an emergent sequence consisting of basal sills, submarine flows (>3 km), pillow breccia and hyaloclastite (<1 1cm), and subaerial flows (>1.5 km). Karmutsen stratigraphy overlies Devonian to Permian volcanic arc (~380-355 Ma) and sedimentary sequences and is overlain by Late Triassic limestone. The Karmutsen basalts are predominantly homogeneous tholeiitic basalt (6-8 wt% MgO); however, the submarine part of the stratigraphy, on northern Vancouver Island, contains ...