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Drift Composition and Surficial Geology of the Trutch Map Area (94G), Northeastern British Columbia

Geological Survey of Canada Open File D3815

Surficial Materials Legend

ICE
O
C
A, At
Af
L
G, Gt
Gi
T(L)
T(C)
Tv
R

 


QUATERNARY

SURFICIAL DEPOSITS

 POST LAST GLACIATION 
GLACIAL ENVIRONMENT
Ice
ICE AND SNOW: Small alpine cirque glaciers and semipermanent snowbanks
NONGLACIAL ENVIRONMENTS
O
ORGANIC DEPOSITS: organic matter; 1 to 2 m thick; formed by the accumulation of vegetation in poorly drained depressions (swamps and bogs)
C
COLLUVIAL DEPOSITS: active and inactive landslides, undivided; mass wasting debris 1-100 m thick
A, At
FLUVIAL DEPOSITS: alluvium; sorted gravel and sand >1 m thick; forming active flood plains A, and terraces At
Af
ALLUVIAL FAN DEPOSITS: poorly sorted gravel and sand >1 m thick
POSTGLACIAL OR LATE WINSCONSINAN

PROGLACIAL AND GLACIAL ENVIRONMENTS

 
L
LACUSTRINE DEPOSITS: fine sand, silt, and clay, deposited in glacier-dammed lakes; > 1 m thick; often overlain by organic deposits in lowlands; level topography
GLACIOFLUVIAL DEPOSITS: gravel, sand, minor sandy diamicton, usually 1 to 40 m thick; deposited by meltwater behind, at, or in front of glacier margins
G, Gt
Proglacial outwash: gravel and sand deposited in front of the ice margin forming distal outwash terraces Gt, or undifferentiated G
Gi
Ice-contact glaciofluvial sediments: coarse sand and gravel interbedded with discontinuous lenses of diamicton
TILL: nonsorted debris deposited directly by glacial ice; matrix is sandy to clayey and contains striated clasts of various lithologies; mountain till is characterized by local rock types and/or with sparse erratics transported westward from the Rocky Moutains; the plains and plateaus in the east are covered by continental till containing many Canadian Shield rocks
T(L)
Laurentide till blanket; > 1 m thick; forming undulating topography that may be fluted and drumlinized in places; contains erratics of eastern provenance
T(C)
Cordilleran/Montane till blanket; > 1 m thick; forming undulating topography that may be fluted and drumlinized in places; contains erratics of western provenance
Tv
undifferentiated till veneer, < 1 m thick and discontinuous; underlying bedrock topography is discernible
PRE-QUATERNARY BEDROCK
R
Sedimentary bedrock. In the west, the Rocky Mountains and foothills are characterized by Paleozoic to Mesozoic rocks forming longitudinal fault- and fold-controlled mountain ranges and valleys trending northward . The east is characterized by flat-lying Cretaceaous shales and cliff-forming sandstone units.
Note: In areas where the surficial cover forms a complex pattern, the area is coloured according to the dominant unit and labelled in decending order of cover.
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