Port Eliza cave: North American West Coast interstadial environment and implications for human migrations [Grotte de Port Eliza : milieu interstadiale de la côte nord américaine occidentale et ses implications pour les migrations humaines].

Résumé

The timing of Late Pleistocene glacial advance, retreat, relative sea level and environmental viability between 25 and 12.5 ka (14C yrs BP) remain a key issue in the feasibility of a coastal migration route for the first North Americans. This is discussed on the basis of stratigraphic, radiometric and faunal data for Port Eliza cave, a raised sea cave, on the west coast of Vancouver Island, British Columbia. Ice cover is indicated by the occurrence of 2 m of laminated clay, representing deposition in a subglacial lake. From immediately below this clay a diverse vertebrate fauna of marmot, vole, marten, cervid and various species of birds and fish was recovered, yielding ages of 18-16 ka. These dates and others from the region show that ice cover on the outer coast was brief, from ca 15.5-14 ka. The fish species indicate that relative sea level was close to the cave and that salmon runs were likely present. The terrestrial vertebrate fauna is consistent with a cool, open parkland environment with maximum summer temperatures cooler than present, these conditions lasted until at least 16 ka. With a diverse fauna and favorable climate, humans could have survived here on a mixed marine-terrestrial diet, confirming the viability of the coastal migration hypothesis for this portion of the route.