The influence of fluvial and glacial watershed dynamics on Holocene sediment accumulation in Cariboo Lake, Columbia Mountains, British Columbia, Canada

Abstract

Records of sedimentation collected from Cariboo Lake, situated in the northern Columbia Mountains, British Columbia, Canada, are analyzed to assess Holocene fluvial and glacial watershed dynamics. The aim of this study is to provide a proxy record of Holocene hydroclimate and glacier change from sediment archives at a higher temporal resolution compared to available records for the Interior Ranges of British Columbia. Deglacial and Holocene sediment accumulation is observed to reach a maximum thickness of 35 m in deep parts of the lake, using sub-bottom acoustic soundings. A transition from massive to well-stratified sediments is observed in the sub-bottom acoustic record during final phases of valley deglaciation in the region (~10.5–9 cal ka BP). Laminae couplets are interpreted to be deposited annually according to two 14C dates and a varve counting chronology. Two long cores, 2.9 and 3.8 m in length, were selected for analysis with estimated basal dates of 2 cal ka BP. Trends in downcore sediment characteristics were linked to environmental changes in the glaciated catchment headwaters at a temporal resolution of ~100 years. Upstream lake filtering of river floodplains and lakes prevented finding a higher temporal resolution linkage between the sediment characteristics and headwater fluvial and glacial activity. Despite some upstream filtering, the Cariboo River was found to be the primary source of sediment to the long core sites. Observed grain size and varve thickness from two long cores show above average trends, which are coincident with cooler temperatures and the primary glacier advances over the last 2 ka.