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TitleSurficial geology, Nogah Creek, British Columbia
AuthorSmith, I R
SourceGeological Survey of Canada, Open File 5306, 2009, 1 sheet; 1 CD-ROM, (Open Access)
LinksMetadata - Métadonnées
Alt SeriesBritish Columbia Ministry of Energy, Mines and Petroleum Resources, Map 2009-2
PublisherNatural Resources Canada
Documentopen file
Maps1 map
Map Info.surficial geology, glacial deposits and landforms, 1:50,000
Mediapaper; CD-ROM; digital; on-line
File formatreadme / lisez-moi
File formate00 (ESRI® ArcExplorer v. 2.0 is included / est fourni); shp; pdf; shx; dbf; tif; JPEG2000
ProvinceBritish Columbia
AreaNogah Creek
Lat/Long WENS-122.0000 -121.5000 58.7500 58.5000
Subjectssurficial geology/geomorphology; glacial deposits; glaciofluvial deposits; tills; alluvial deposits; fluvial deposits; organic deposits; eolian deposits; glacial features; glacial landforms; moraines; glacial history; lacustrine deposits; glaciolacustrine deposits; colluvial deposits; Cenozoic; Quaternary
Released2009 04 28
AbstractThe Nogah Creek (NTS 94I/12) map sheet was inundated by the Laurentide Ice Sheet during the late Wisconsinan glaciation (ca. 25 000 - 10 000 years ago). Bedrock was not encountered during field operations anywhere in the map area, instead thick clay and fine-silt-rich till deposits appear to blanket almost the entire region. One particularly deep borrow pit exposed >24 m of till, suggesting that thrusting and stacking of till sheets is likely to have occurred. The remarkably flat topography, coupled with the relative impermeability of the regional till has led to surface ponding of water and the development of extensive organic fen and bog deposits. Given the impermeability of the till, much of the area is characterized by a perched aquifer at surface. Several borrow pits dug in such a manner as to prevent surface drainage from the surrounding peatlands into them were observed to remain dry, excepting that attributable to meteoric water accumulation, for two or more years. This suggests that the groundwater table is situated well below surface. Where peat has accumulated, it is likely underlain by permafrost, and probably contains significant amounts of ground ice as evidenced by extensive thermokarst and kettled topography.

During deglaciation, the region was occupied by an increasingly lobate eastward retreating ice mass. Moraines in the southern part of the map area likely record terminal ice margin positions, while large meltwater channels in the northern map area correspond to drainage along earlier lateral ice margins. The southwestern corner of the map area borders what is interpreted to have been a subglacial tunnel valley. Evidence in support of this interpretation include its regional morphology, the presence of extensive glaciofluvial sand and gravel deposits flooring its base and lateral margins that are capped by 1-4 m of till, and moraines that drape the landscape, transverse to the long-profile of the valley. The sub-till gravel deposits (Tb/Gt) were exposed in numerous borrow pits dug during construction of the Nogah side road. There, 1-4 m of clay-rich till overly, 2-4 m of well sorted, foreset and planar-cross bedded fine to medium gravels and sand. Used opportunistically to top-dress local roads, these deposits are projected to extend laterally across a 5 x 0.5 km area, but pale in comparison to the enormous (>1 million m3) Elleh Creek coarse gravel deposit situated 5 km to the southwest of the map area.