CGRG Bibliography of Canadian Geomorphology
Search Results
Author : Cockburn, J.M.H.; and Lamoureux, S.F.
Date : 2004.
Title : Major autumn rainfall events in northwestern North America in association with Little Ice Age glacial activity.
Publication : 49th Annual Meeting of the Geological Association and the Mineralogical Association of Canada. May 12-14, 2004. Brock University, St. Catharines, Ontario.
Issue :
Page(s) :
Abstract
In the past, annually laminated (varved) sediments from glacially-fed lakes have provided valuable records of Little Ice Age (LIA) glacial activity, particularly advance and retreat phases. At White Pass in the northwestern Coast Mountains along the British Columbia/Alaska border, we constructed varve records from two adjacent glacially-fed lakes to investigate the LIA dynamics in this region. The record from Summit Lake extends to 1299 AD and consists of varves with complex subannual laminae that likely represent hydrologically-induced sedimentary events (e.g. nival-glacial runoff, rainstorm runoff). Under certain conditions, river discharge events produce subannual sedimentary events within a varve. A comparison of modern discharge and precipitation records with detailed varve sedimentology indicates that the late season sedimentary events are likely produced by rainfall induced runoff and sediment transport into Summit Lake. The frequency and thickness of rainfall induced sedimentary events increased substantially and abruptly at ca. 1675 AD. The second lake (Meadow Lake) provides a continuous varved sequence extending to 1677 AD and was discontinuous prior to that time. The onset of continuous varve formation at Meadow Lake is related to increased sedimentation rates that we attribute to increased glacierization of the cirques in this watershed. Increased glacial activity indicated in Meadow Lake, together with the more frequent subseasonal sedimentary events attributed to autumn rainfall in Summit Lake, suggests that early LIA glacier advances in this area were coincident with an increased frequency in autumn rainfall. These results suggest that moisture was an important control over LIA glacial activity in the White Pass region.
Bibliography of Canadian Geomorphology