CGRG Bibliography of Canadian Geomorphology
Search Results
Author : Ferbey, T.; and Levson, V.M.
Date : Late Wisconsinan ice-flow reversals at the British Columbia Coast mountain/interior plateau transition: stratigraphic, lithologic, and geochemical evidence
Title : Late Wisconsinan ice-flow reversals at the British Columbia Coast mountain/interior plateau transition: stratigraphic, lithologic, and geochemical evidence
Publication : Water, Ice, Land, And Life: The Quaternary Interface. Canadian Quaternary Association 2005 Conference June 5-8, 2005, University of Manitoba, Winnipeg, Manitoba.
Issue : Abstract Volume:
Page(s) : A25.
Abstract
The Coast Mountain/Interior Plateau transition in west-central British Columbia experienced a complex ice-flow history during the Late Wisconsinan Fraser Glaciation. Cross-cutting and superimposition relationships constrain the relative timing of ice-flow events and indicate that a westerly-directed ice-flow event occurred during the glacial maximum. Glaciers flowed west, towards and over the Coast Mountains from the Interior Plateau. This event was preceded and followed by smaller magnitude east to northeast ice-flow events from ice centres in the Coast Mountains. These ice-flow reversals can be explained by the existence of an ice divide in the central interior during the Fraser Glaciation maximum. Detailed data was collected in the Huckleberry Mine region to investigate the stratigraphic, lithologic, and geochemical record of the ice-flow reversals. Basal tills dominate the Quaternary stratigraphy and multiple till units were distinguished primarily by changes in matrix texture, colour, clast content, and geochemistry. Pebble fabrics in the lower till units show strongly preferred clast orientations that indicate deposition during southeastward to eastward ice-flow events. These data provide stratigraphic evidence of an early, eastward-directed, ice flow event. Deposition during this event is further supported by a striated clast pavement that contains numerous faceted, striated, and glacially streamlined clasts with ice-flow indicators (e.g. rat-tail, smoothed and plucked faces) that suggest valley-parallel ice-flow (to the east-southeast). Lithology and geochemical data also support ice-flow reversals in the region. Lower till units at a 19 m section contain <5% porphyritic granodiorites. There are no documented outcrops of granodiorite west of this section, but <1 km to the east is a mineralized (Cu+/-Mo) porphyritic granodiorite stock. The general lack of granodiorite clasts in lower till units suggest a western provenance. An increase in granodiorite clasts of up to 27% in the upper tills at this section suggest that westerly flowing ice eroded the stock to the east. Till geochemical data also support this interpretation. Maximum copper values occur in the upper till unit (234 ppm), while the lower two tills have only minor copper concentrations (<20 ppm). Locally developed dispersal trains in the area also record transport of mineralization towards both the east and west. Two westward-directed dispersal trains with copper concentrations >1000 ppm are isolated and distant from the mineralized areas and suggest that there may still be undiscovered bedrock mineralization on Huckleberry Mine property.
Bibliography of Canadian Geomorphology