A MULTI-PROXY STUDY OF PORT ELIZA CAVE AND THE IMPLICATIONS FOR A HUMAN COASTAL MIGRATION ROUTE

Port Eliza cave is a wave-cut cave 85m a.s.l. on the west coast of Vancouver Island, British Columbia. This cave provides direct information on both the timing and extent of ice cover and the associated paleoenvironmental conditions, both of which are essential to the evaluation of the coastal migration hypothesis. A multi-proxy study using sedimentology, palynology, palaeontology and geochronology indicates that a diverse fauna and favourable climate existed until at least 16 ka, prior to ice cover during the Late Wisconsinan. This demonstrates that human migration along the coast of Vancouver Island was possible.

Three units were identified and interpreted to represent deposition before, during and after glaciation. Unit 1 is a diamicton and represents the palaeo-floor of the cave containing abundant bone material, clasts of varying lithology, size and shape, and fragments of dripstone. The genesis of Unit 1 is characterised by textural as well as SEM analysis. Carbon-14 ages of 18.0-16.3 ka from bones constrain ice-free conditions on the outer coast. Uranium series dating of dripstone fragments may further refine the duration of this ice-free period. Unit 2 comprises laminated silts and clays and was deposited in a glaciolacustrine environment formed when the cave mouth was blocked by ice, sometime after 16 ka. The presence of strong remnant magnetisation supports deposition from suspension settling and also allows tentative correlation with other Late Wisconsinan deposits. The glacial origin and clay minerology of these rhythmites will be analysed through thin section, XRD, and SEM analysis. Unit 3 is a post glacial deposit consisting of oxidised clay containing dripstone and charcoal fragments, and the remains of a mountain goat that yielded a Carbon-14 age of 12.3 ka.

The interstadial environment was reconstructed from Unit 1. A diverse fauna of marmot, vole, marten, cervid and various species of birds and fish, indicate a relatively productive environment. Pollen data and terrestrial fauna are consistent with an open parkland environment with maximum summer temperatures cooler than present. These conditions lasted until at least 16 ka, indicating that prior to Late Wisconsinan glaciation, humans could have survived in the Port Eliza area on a mixed marine-terrestrial diet.