PhD Dissertations: James M. White, 1983

Late Quaternary Geochronology and Palaeoecology of the Upper Peace River District, Canada

Pollen percentage and influx analyses and influx analyses and radiometric dating of sediment cores from three lakes in the Peace River district of northeastern British Columbia and northwestern Alberta were used to investigate the regional Late Quaternary geochronology and palaeolecology. Microfossil and macrofossil analyses of a basal core segment from Boone Lake showed that two 14 C ages greater than 12,000 years B.P. were spuriously old due to Cretaceous age organic contamination. The sedimentary record began in Boone Lake about 12,000 years B.P. during deglaciation, and sedges dominated a diverse aquatic and upland vegetation close to receding ice. A poplar-willow-sage-grass-sedge zone occurred probably prior to 11,600 years B.P., indicating a humanly habitable 'Ice-free Corridor' in the Saddle Hills. A major poplar decline took place at about 10,800 years B.P., probably because of increasing competition from conifers. The forest was similar to modern boreal coniferous forest with more abundant shrubs and herbs. It is considered unlikely that spruce could have migrated from the central prairies to Beringia by 11,500 years B.P. without becoming established in the Peace River area prior to 10,400 years B.P. The regional pine presence at 10,400 years B.P. sets a minimum age for the withdrawal of Glacial Lake Peace to the Indian Creek Stage, and for the cessation of regional periglacial activity. A possible minor climatic regression took place about 10,000 years B.P. Tree birch became an important forest element between 8700 and 8200 years B.P., followed by a pine peak at 7400 years B.P. which is interpreted as the Hypsithermal maximum. No significant expansion of the Peace River grasslands took place during the Hypsithermal. A trend to wetter conditions began around 7400 years B.P., with the establishment of some permanent ponds by about 5100 years B.P. A minor spruce decline and alder increase has taken place in the last 3400 years. The application of a non-parametric statistical technique is proposed as a test for randomness of distribution of uncommon pollen types.