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TitleSurficial geology of the Sept-Îles area, Quebec North Shore
LicencePlease note the adoption of the Open Government Licence - Canada supersedes any previous licences.
AuthorDredge, L A
SourceGeological Survey of Canada, Memoir 408, 1983, 40 pages, Open Access logo Open Access
MapsPublication contains 1 map
Map Info.surficial geology, 1:250,000
Mediapaper; on-line; digital
RelatedThis publication contains Surficial geology, Sept-Îles, Quebec
File formatpdf
NTS22G/05; 22G/06; 22G/11; 22G/12; 22G/13; 22G/14; 22G/15; 22J/01; 22J/02; 22J/03; 22J/04; 22J/05; 22J/06; 22J/07; 22J/08
Lat/Long WENS-68.0000 -66.0000 50.5000 49.2500
Subjectssurficial geology/geomorphology; economic geology; paleontology; sedimentology; igneous and metamorphic petrology; stratigraphy; eolian deposits; deglaciation; alluvium; eskers; glaciofluvial deposits; landslide deposits; marine deposits; organic deposits; till stratigraphy; bedrock geology; groundwater; wisconsinian glacial stage; Laurentian Channel; Precambrian; Quaternary
Illustrationsblock diagrams; diagrams; charts; photographs; correlation charts
Released1983 05 01; 2013 10 29
AbstractThe Sept-Iles map area lies along the Quebec North Shore - a rugged upland hinterland of rounded Precambrian hills and a terraced coastal plain of late Quaternary marine sediments. Surface materials are divided into ten genetic units: bedrock outcrop; sandy till; outwash; a marine offlap sequence consisting of massive and rhythmically bedded silty marine clay. silty deltaic foreset sand. littoral sand and tidal flat clay; alluvium; eolian sand; and peat. Mamillated bedrock hills and large valleys graded to below sea level were developed prior to the last glaciation, ill all surficial deposits relate to the last glacial episode and postglacial events. The main ice flow was to the southsoutheast, although striae along the coast in the southern part of the study area indicate early and very late easterly ice flow within the Laurentian channel. The limit of the late Labradorean grounded ice sheet lay about 50 km south of the present coast near Sept-fles and near the coast in the vicinity of Godbout. Upon deglaciation. which occurred about 9000 to 10 000 years ago in the Sept-fles area and somewhat earlier (13 500? years ago) near Godbout. the Goldthwait Sea inundated the region. Marine limit rises from 100 m near Godbout to 130 m at Sept-fles. Below marine limit a thick marine offlap sequence was deposited as the land emerged. Sediment-laden meltwater poured through pre-existing valleys and debouched into the regressing sea to form coalescing deltas. which were subsequently terraced to present sea level. Above marine limit sandy, poorly stratified meltout and flow till were deposited as ice retreated northwards. Two major morainic belts trend southwest-northeast: The Baie-Trinite moraines are small, subparallel features; they lie near the edge of the Laurentian channel and may have been emplaced along shear planes in brittle ice near the limit of glaciation. The Laurentian Upland and Daigle moraines are part of a larger morainic system stretching hundreds of kilometres along the North Shore and are associated with a major interruption in the general pattern of ice retreat. Settlements and transportation corridors are concentrated along the coastal plain. which is underlain by sensitive marine clays subject to flowsliding. The clays are nonplastic and have water contents which slightly exceed the liquid limit. Flowslides or semicircular rotational slips occur where slopes are overstepened or where excessive porewater pressures develop as a result of natural or man-induced disturbance.

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