Full Title: The Late Cretaceous San Juan Thrust System, San Juan Islands, Washington
Authors: Mark T. Brandon, Darrel S. Cowan, and Joseph A. Vance
The San Juan Islands expose a thick and regionally extensive sequence of Late Cretaceous thrust faults and nappes, referred to as the San Juan thrust system. Straddling the southeastern edge of the Wrangellia terrane of Vancouver Island, this system contains important information on the accretionary history of Wrangellia and other, related, far-traveled terranes. The authors identify five within, and peripheral to, the thrust system, which were widely separated from each other, and also from Wrangellia, until the Late Jurassic: (1) the Haro, an Upper Triassic arc-volcanic sequence; (2) the Turtleback, a Paleozoic arc-plutonic and volcanic unit; (3) the Deadman Bay, a Permian to Lower Jurassic oceanic-island sequence; (4) the Garrison, a Permo-Triassic, high-pressure metamorphic unit; and (5) the Decatur, a Middle to Upper Jurassic ophiolite and superimposed arc-volcanic sequence. They conclude that the system is a short-lived collision-like orogen rather than a long-lived subduction complex.