Abstract

The Decatur terrane is a small, allochthonous fragment of Upper Jurassic oceanic crust with an overlying blanket of Upper Jurassic-Lower Cretaceous sedimentary rocks in the San Juan Islands. The stratigraphy and petrotectonic elements are dissimilar to those of coeval sequences in the Pacific Northwest (Oregon, Washington, and southern British Columbia), but are virtually identical to those of the Coast Range ophiolite and overlying Great Valley sequence south of San Francisco, California. This stratigraphic correlation, together with regional considerations, suggests that the Decatur terrane was detached and transported during Cretaceous time. The resultant displacement is in excess of 1000 km.

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