The Kootenay Group , originally called the Kootenay Formation , is a geologic unit of latest Jurassic to earliest Cretaceous age in the Western Canada Sedimentary Basin that is present in the southern and central Canadian Rockies and foothills. It includes economically important deposits of high-rank bituminous and semi-anthracite coal , as well as plant fossils and dinosaur trackways .
15-715: The strata of the Kootenay Group were originally described as the Kootenay Formation. D.W. Gibson revised the sequence as the Kootenay Group and defined it as encompassing the stratigraphic interval between the Jurassic Fernie Formation and the Lower Cretaceous Blairmore Group . He subdivided it into three formations as shown below and designated a type section for each of the formations, thus eliminating
30-401: A higher propensity for containing a significant clay fraction. Although often mistaken for a shale , siltstone lacks the laminations and fissility along horizontal lines which are typical of shale. Siltstones may contain concretions . Unless the siltstone is fairly shaly, stratification is likely to be obscure and it tends to weather at oblique angles unrelated to bedding. Siltstone
45-707: A maximum thickness of about 1,355 metres (4,450 ft), and it thins eastward. The Kootenay Group conformably overlies the marine shales of the Fernie Formation. In most areas it is disconformably overlain by the nonmarine strata of the Blairmore Group , although in some western areas the contact may be conformable. North of the North Saskatchewan River the Kootenay Group grades into the Nikanassin Formation . To
60-798: Is an unusual rock, in which most of the silt grains are made of quartz . The origin of quartz silt has been a topic of much research and debate. Some quartz silt likely has its origin in fine-grained foliated metamorphic rock, while much marine silt is likely biogenic, but most quartz sediments come from granitic rocks in which quartz grains are much larger than quartz silt. Highly energetic processes are required to break these grains down to silt size. Among proposed mechanism are glacial grinding; weathering in cold, tectonically active mountain ranges; normal weathering, particularly in tropical regions; and formation in hot desert environments by salt weathering. Siltstones form in relatively quiet depositional environments where fine particles can settle out of
75-401: Is composed mostly of silt . It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility . Although its permeability and porosity is relatively low, siltstone is sometimes a tight gas reservoir rock, an unconventional reservoir for natural gas that requires hydraulic fracturing for economic gas production. Siltstone
90-623: The Monteith Formation in northeastern British Columbia . It rests disconformably on Triassic units in the west, and unconformably on upper Paleozoic units such as the Schooler Creek Group and the Montney Formation farther east. The Fernie Formation has the following subdivisions from top to base: Siltstone Siltstone , also known as aleurolite , is a clastic sedimentary rock that
105-706: The longitude of Calgary . The formation is exposed in outcrops in the Kootenay region of southeastern British Columbia , in the foothills and front ranges of the Canadian Rockies in southwestern Alberta, and as far north as the Peace River Country in northeastern British Columbia. The Fernie Formation is conformably overlain by the Morrissey Formation in the south, by the Nikanassin Formation in central Alberta and by
120-687: The Morrissey Formation, but the Mist Mountain Formation includes plant fossils and dinosaur trackways , and the Elk Formation includes plant fossils, trace fossils and bivalves . The Kootenay Group is present in the front ranges and foothills of the Canadian Rockies in southeastern British Columbia and southwestern Alberta. It extends from the Canada–US border to north of the North Saskatchewan River . It has
135-557: The clay and silt fraction is composed of silt-sized particles. Silt is defined as grains 2–62 μm in diameter, or 4 to 8 on the Krumbein phi (φ) scale . An alternate definition is that siltstone is any sedimentary rock containing 50% or more of silt-sized particles. Siltstones can be distinguished from claystone in the field by chewing a small sample; claystone feels smooth while siltstone feels gritty. Siltstones differ significantly from sandstones due to their smaller pores and
150-605: The east during the deposition of the lower and middle units of the Fernie, where the coarser facies occur in the eastern part of the formation. In the uppermost Fernie, the coarsest material is found in the west, however, indicating a shift to sources in the west and south. The Fernie Formation is composed primarily of brown and dark gray to black shales that range from massive with conchoidal fracture to laminated and highly fractured or papery. Phosphatic sandstone and limestone , including cherty limestone , occur locally in
165-480: The lower parts of the formation ; siltstone , sandstone , coquinas and oolitic limestone interbeds can occur in the center; glauconitic sandstone and siltstone can be present in the upper parts. The Fernie Formation reaches a maximum thickness of 400 metres (1,310 ft) near Mount Allan in Alberta, and typically is about 70 to 150m (230 to 492 ft) thick. It thins toward the east, disappearing at about
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#1732790189921180-511: The need for a type section for the group. The Kootenay Group is an eastward-thinning wedge of sediments derived from the erosion of newly uplifted mountains to the west. The sediments were transported eastward by river systems and deposited in a variety of river channel , floodplain , swamp , coastal plain , deltaic and shoreline environments along the western edge of the Western Interior Seaway . Fossils are rare in
195-772: The south it may correlate with the upper part of the Morrison Formation in Montana. It was originally mis-correlated with the Kootenai Formation which underlies the Morrison. Fernie Formation The Fernie Formation is a stratigraphic unit of Jurassic age . It is present in the western part of the Western Canada Sedimentary Basin in western Alberta and northeastern British Columbia . It takes its name from
210-677: The town of Fernie, British Columbia , and was first defined by W.W. Leach in 1914. The Fernie Formation consists of marine sediments that were deposited in the Sundance Sea . Deposition took place throughout most of the Jurassic period, starting during the Hettangian stage in some parts of northeastern British Columbia and continuing until the mid-Tithonian , as determined from its fossil assemblages, including ammonites , molluscs and microfossils . The sediments were sourced from
225-419: Was prized in ancient Egypt for manufacturing statuary and cosmetic palettes . The siltstone quarried at Wadi Hammamat was a hard, fine-grained siltstone that resisted flaking and was almost ideal for such uses. There is not complete agreement on the definition of siltstone. One definition is that siltstone is mudrock ( clastic sedimentary rock containing at least 50% clay and silt) in which at least 2/3 of
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