The Channel Islands, like the Salinian block, have been explained as a granitic spur projecting westward into the Franciscan realm of coastal and offshore California. According to Ralph Reed, this spur was the autochthonous Anacapia, but according to P. B. King, the spur was an allochthonous sliver derived by lateral fault movement.

Both interpretations require a boundary fault south of the Channel Islands; actually, the fault picture is more complex. The Malibu Coast fault, arcuate and convex southward in plan, appears to extend from Beverly Hills across the Mugu-Hueneme submarine fan into the eastern Santa Barbara Channel north of Anacapa Island. The Santa Cruz Island fault, also convex southward, continues south of Anacapa.

San Onofre Breccia flanks both faults. San Onofre paleocurrent indicators on Santa Cruz Island and limited San Onofre outcrops on the northern tip of Santa Rose Island indicate the blueschist basement source was northeast of the Santa Cruz Island fault, thereby invalidating the Anacapia spur-silver concept. Instead, Anacapia is a microcontinent of granite with a Cretaceous-Eocene sedimentary veneer. The granite tectonically overlies Franciscan and is separated from the mainland by a rift bounded by the Malibu Coast and Santa Cruz Island faults.

The pre-Mohnian terrane in the rift is mainly volcanic, and presumably overlies Franciscan basement. This basement was exposed during Miocene time, when the Channel Islands raft drifted westward from the Santa Monica Mountains. At first, the ductile Franciscan welled up in the rift as a tectonic ridge, shedding San Onofre talus on either side. Subsequently, the ridge in the rift sank, and gravity tectonics were produced in the Santa Monica Mountains.

Palinspastic restoration of the 80-km lateral offset and the 20-km rift extension brings together similar Cretaceous-Eocene sequences of the Channel Islands and Santa Monica Mountains, and connects Poway Conglomerate clast assemblages of the islands with their mainland source.

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