Annotation: Richardson Island Stratigraphy

Annotated stratigraphy of lowest Richardson Island archaeological deposits.

Richardson Island is a remarkable archaeological site in southern Haida Gwaii.  When it was occupied, sea levels were about 10 metres higher than today, and rising.  Then, sea levels stopped rising and occupation continued.  We have dates ranging from 10,500 cal BP to 2900 cal BP (calendar years before present).  However, the early part of the record includes the most impressive stratigraphy.  The shoreline configuration at that time likely included a supra-tidal marine berm feature, which would have had a flattish top and have been well-drained and probably vegetation free: a perfect place to camp.  Occasional storms or even tsunamis would build this berm in the winter, and with rising sea levels the berm was “pushed uphill” so to speak.  The berm-building process would have involved sudden dumps of sorted pea-gravel onto the occupation layers at the site, sealing and preserving them.  Overall, though, the site is in a well-protected location, at least relative to the enormously dynamic winter sea conditions of Haida Gwaii.

Fieldwork Picture of the Day 3

Profiling the south wall of the Richardson Island site 2002

The Richardson Island site (map) is a deeply stratified raised beach site.  In this picture, Duncan’s feet are at about 9300 14C years ago, while the top of the gulch is about 8400 14C years ago.  The horizontal 2 X 4 more or less demarcates the lower “Kinggi Complex” from the “Early Moresby Tradition” – the latter being marked by the introduction of bifacial technology to the stone toolkit, but also characterized by continuity between the two in many other regards.  There are some 20 major depositional units in that span, and more than 100 separable layers.  We think the site formation process is of a supra-tidal marine berm which was “pushed uphill” during a period of rising sea level — people lived on top of this berm but would periodically come to the site and find a fresh dump of finely-sorted pea gravels.   Although high-energy, the berm formation was also surprisingly gentle, allowing for numerous features such as hearths and post-moulds to preserve, not to mention pristine flakes which, in some cases could be refit one to another.  The thick reddish band just above Duncan’s head is a major berm deposit which was dumped as a single event, or several shortly-spaced events, around 9200 14C years ago.   Digging this site was a challenge – some of the layers were concreted together like iron and required some chiseling, and colour differences between some layers were often very slight.  Indeed, it became a full body experience as the texture and looseness of the gravels was very important, and on occasion, it was noted that some layers smelled differently than others.