| Kootenay Group | |
| Type: | Group |
| Period: | Mesozoic |
| Prilithology: | Sandstone, siltstone, mudstone |
| Otherlithology: | Coal, conglomerate |
| Namedby: | D. W. Gibson, 1979[1] |
| Region: | Canadian Rockies |
| Country: |  Canada |
| Subunits: | Elk Formation Mist Mountain Formation Morrissey Formation |
| Underlies: | Blairmore Group |
| Overlies: | Fernie Formation |
| Thickness: | maximum 1335-1NaN-1 |
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.[2] It includes economically important deposits of high-rank bituminous and semi-anthracite coal,[3] as well as plant fossils and dinosaur trackways.
The strata of the Kootenay Group were originally described as the Kootenay Formation.[4] 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 the need for a type section for the group.
| Maximum Thickness | Reference | ||||
|---|---|---|---|---|---|
| interbedded sandstone, siltstone, mudstone, conglomerate; rare thin coal seams | 590-1NaN-1 | ||||
| interbedded sandstone, siltstone, mudstone, shale, and mineable coal seams; rare conglomerate | 665-1NaN-1 | ||||
| 80-1NaN-1 |
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.[5]
Fossils are rare in 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 a maximum thickness of about 1355m (4,446feet), and it thins eastward.[6]
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.[7]
North of the North Saskatchewan River the Kootenay Group grades into the Nikanassin Formation. To 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.