PALEOENVIRONMENTAL ANALYSIS OF NAMU LAKE, BRITISH COLUMBIA

• Main Author: Brown, Alyson
• Other Authors: Reinhardt, Eduard, Earth Sciences
• Format: Thesis
• Language: English
• Published: 2016
• Subjects: particle size analysis; trace elements; lake sediments; prehistoric settlement; Pacific; Sockeye; Pink salmon
• Online Access: http://hdl.handle.net/11375/20574

Pacific salmon has been a staple resource for residents of British Columbia for over seven thousand years. Archaeological evidence obtained from a shell midden at Namu, B.C., provides detailed information about the diets of the First Peoples living at Namu over the past seven thousand years. Pacific salmon was the most prevalent species of fish uncovered within the midden, excluding herring. Pink, chum and sockeye species were consumed in the greatest quantities. Pink was particularly favored because of its ability to store over winter months without spoiling. Evidence from the shell midden also reveals fluctuations within the pink salmon fishery from ~3800 until 1900 cal year BP. The paleoenvironmental conditions within Namu Lake during the time of the pink collapse have never before been explored. There is also little evidence pertaining to what may have contributed to the collapse of the pink fishery. Sediment cores collected from Namu Lake, B.C. provide evidence for paleoenvironmental conditions that may have contributed to fluctuations in the pink salmon population. Particle size analyses of lake sediment cores indicate changes in river discharge as well as erosional intensity within the Namu basin. Particle size, coupled with radiocarbon dating, reveal a transitional period within the basin from ~ 3200 to 2200 cal year BP. A decrease in elemental ratios/Al, particularly Ca, Na, Ba, and Sr, provides evidence for a decline in erosional intensity and a relatively drier period within the basin. The decrease in erosional intensity could be due to consistently drier conditions at Namu. A resulting reduction in the flow of the Namu River would have caused an increase in finer particles within the pink salmon spawning grounds. Average C/N ratios for NC1 are 26.28, indicating that organic matter within the lake is mainly terrestrial in origin. These results, combined with the particle size and trace metal analysis, reveal that river discharge and slope wash had declined during this period causing fine material to remain in the Namu River (outflowing), which is the spawning grounds for the pink salmon, rather than being transported out into the bay. The results of this study reveal that a shift in moisture, towards relatively dry conditions, negatively impacted spawning pink salmon at Namu Lake. This study provides insight into the sensitivity of Pacific salmon to climate and the effects future climate change may have on the species. The ability of environmental data to supplement and enhance archaeological information and interpretations of prehistoric conditions is illustrated throughout this study. The cores collected at Namu Lake also reveal the need for site specific climatic data in order to accurately interpret archaeological contexts and conditions. Thesis Master of Science (MSc)