Dynamics of a holocene cliff-top dune along mountain river, northwest territories, Canada

The dynamics of a cliff-top dune system located at the foot of the Mackenzie Mountains was reconstructed by radiocarbon dating and tree ring analysis of forest paleosols in eolian sediments, The first evidence of eolian activity dates to ca, 3000 yr B.P. when the breaching of a bedrock sill initiated the erosion of glaciofluvial deposits that resulted in the exposure of a 75-m-high cliff of erodible sediment, Sandy sediment eroded from the cliff by katabatic winds from the Mackenzie Mountains buried a mature forest growing on alluvial sediments, Despite a minor eolian event between 750 and 860 cal yr A.D., dune development began ca, 1100 cal yr A.D. and has been marked by two major sedimentation periods between ca, 1100 cal yr A.D. and 1460 A.D. and from 1865 to present, Detailed analysis of tree morbidity and mortality indicates that the dune progressed at an average rate of 78 cm/yr for the last century. Dune dynamics are directly related to slope activity that controls the episodic nature of sediment availability and to the katabatic wind regime. Comparison of the dune dynamics and paleoclimatic data suggest a possible influence of warm climate on eolian activity. (C) 1995 University of Washington.