Abstract

Recent studies in the northern Cordillera suggest that a significant period of middle Cretaceous extension occurred during the early phases of the collision of the composite Peninsular-Alexander-Wrangellia (PAW) superterrane. In this paper I present a hypothesis that the extension and collision are related in a manner analogous to the modern eastern Mediterranean. In the model, oblique collision of the PAW superterrane led to gravity spreading on North America in advance of the zipper-like closure of the suture. The driving process for the extension appears to be subduction rollback generated by collision-related changes in plate motion, gravity spreading toward the "free-face," or both.

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