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south than presently. The Kootenay River floc+plain gradually grey,
through'centinuous .deposition of.material into this water body. The
alluvialsediments were then .dep'osited during annual spring floods..
Medium silt to coarse sand deposits formed.natural levees adjacent to
the river, while the finer sediments are carried across the levee
depositing.only-in quiet backwater swamps and temporary lakes.' This
type of flooding is clearly evident by the large areas of utxiformte~ured
deposits. Texture variations do occur but are restricted to abandoned
channel areas, and stream entrantes from the adjacent mountains. These .
deposits vary 20 feet in elevation from a low of 1,744 feet to a high
of 1,764 feet.
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GLACIOLACUSTRINE DEFQSITS
The lacustrine deposits occur on the,higher bench ,lands up to
approximately 2,&JO feet'in elevation. The origin of this deposit
occurred during the,melting stages of the last.ice retreat. The main
valley bottom probably contained the glacier for the longest period of
time. The ice prevented or blocked the normal drainage system,
impounding meltwaters between the glacier and the highlands. Into
these temporary basins the meltwater streams discharged sediment.
During spring and summer most of the melting'occurs, resulting in '.'- !.
greater movement and deposition of coarser sized particles while during
times of less turbulent water find clay sized particles settled to the
bottom. This process results in a layering effect (called varves)
common in many lacustrine, deposits;-.. The 'stones.;and-'boulders found in
these deposits were carried in by ice probably during the freshet
season. The topography. reflects.th~._~~~-rSlng relief. only -when.&he.
lacustrine deposit becomes shallow.
GLACIAL TILL
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Glacial till deposits appear to underlie’ the glaciolaCtist’rin& aieas
and only occur on protruding knolls or in areas where the lacustrïne
sediments had been completely eroded- away: . . The origin of glacial till takes place during active ice movementI.
Glaciers slowly creep over the land abrading and quarryingbedrock aiad..:-::.:
plastering or filling in hollows over which it passes. Basically the
glacier a&s,.as a,land leveller by acraping off high' spots and filling ,:,%,;,
in low.pockets. This process takes .place. wàth'relatively little w&ter
action resulting in,:a characteristic unsort& mater&1 termed till;"“" '-
Till composition varies from region to region and valley to valley
but usually localized areaa tend to be fairly uniform.. Its compositionoften
reflects local bedrock but is greatly influenced by the distance..
which the glacier has moved: Thus, large.broad valleys Will Contain .'
tills that include material from local and distant sources.