Abstract

Along the south shore of Bainbridge Island and north shore of the Kitsap Peninsula, Wash., the Blakeley Formation of Weaver (1912), consists of approximately 2,400 m of volcaniclastic sandstone, conglomerate, mudstone, and shale that is interpreted to be part of an ancient submarine fan complex. Three lithofacies units of Oligocene age are recognized within the sequence. The oldest unit consists of poorly-sorted ungraded disorganized conglomerate, subordinate graded organized conglomerate, and interbedded mudstone and turbidite sandstone beds assigned to the Refugian and Zemorrian Stages. A second conglomeratic unit consisting of Zemorrian strata is interpreted to be a channel facies eroded into and emplaced within the underlying Refugian sequence. The two conglomerate-bearing lithofacies grade upward into a fine-grained sandstone and siltstone succession approximately 1,100 m thick that is interpreted to be an outer-fan (distal) turbidite sequence. Sedimentary structures (flute casts, crossbedding, and imbricated clasts) indicate westward transport of sediment, probably from a Cascade Range source terrane. Deep water turbidite sedimentation suggests that the Blakeley Formation was deposited in a deep marginal basin similar to modern basins in the southern California borderland.

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