Abstract

The fate of the Santo Cristo de Burgos galleon (1693) is established from 1) alongshore dispersals of shipwreck artifacts prior to the 1700 Cascadia earthquake, 2) shipwreck artifacts deposited by 1700 tsunami surges in beaches and estuary wetlands, and 3) post-1700 subsidence catastrophic beach retreat in the Manzanita-Nehalem study area. Shipwreck structures, unabraded sherds, and historically salvaged beeswax blocks and tropical wood timbers, are associated with the 1700 tsunami overtopping of the Nehalem Bay sand spit. However, a rapid ship breakup and alongshore dispersal of shipwreck debris must have occurred during the 7 years between the loss of the galleon and the 1700 great earthquake and associated nearfield tsunami surges. The pre-1700 alongshore distribution of recovered artifacts argue for a primary shipwreck site located offshore of the Nehalem Bay sand spit. Measured ocean beach tsunami runup, including high-velocity flow (8 m elevation) likely resulted in further dismemberment of shipwreck superstructures and remobilization of shipwreck flotsam to elevated dune ramps and the over-washed sand spit. Inshore tsunami runup elevations in the lower bay wetlands (3.5 m elevation) and upper bay floodplains (2.7 m elevation) permitted shipwreck flotsam dispersal to reach up-channel distances of 14 km. Catastrophic beach retreat (130 m landward of modern beaches) following the 1700 coseismic coastal subsidence (~1.0 m) would have further eroded beached shipwreck structures. However, backwashed ceramic artifacts could have been initially buried by accommodation space filling (£1.0 m) in the innermost shelf. Subsequent storm wave remobilization of buried sherds and their transport to headland bounded shoreline entrapments continues to the present. The rapid breakup and pre-1700 alongshore dispersal of the Beeswax Wreck debris, could explain the lack of remaining shipwreck structures for two other lost galleons, the San Agustín (1595) and San Juanillo (1578), on the high-energy central west coast of North America.

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