| Fernie Formation | |
| Type: | Geological formation |
| Age: | Jurassic ~ |
| Period: | Jurassic |
| Prilithology: | Shale |
| Otherlithology: | Sandstone, siltstone, limestone |
| Namedfor: | Fernie, British Columbia |
| Namedby: | W.W. Leach |
| Year Ts: | 1914 |
| Region: | |
| Country: |  Canada |
| Coordinates: | 49.55°N -115.16°W |
| Subunits: | Nordegg Member, Red Deer Member, Poker Chip Shale, Lille Member, Rock Creek Member, Highwood Member, Pigeon Creek Member, Ribbon Creek Member |
| Underlies: | Morrissey Formation, Nikanassin Formation, Monteith Formation |
| Overlies: | Schooler Creek Group, Montney Formation, Rundle Group |
| Thickness: | up to 400m (1,300feet)[1] |
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.[2] [3] It takes its name from the town of Fernie, British Columbia, and was first defined by W.W. Leach in 1914.[4]
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.[3] [5]
The sediments were sourced from 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.[1] [6]
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 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.[1] [6]
The Fernie Formation reaches a maximum thickness of 400m (1,300feet) 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 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.[1] [6]
The Fernie Formation is conformably overlain by the Morrissey Formation in the south, by the Nikanassin Formation in central Alberta and by 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.[1] [6]
The Fernie Formation has the following subdivisions from top to base:
| Lithology | Reference | |||
|---|---|---|---|---|
| Passage Beds | dark grey splintery shale interbedded with siltstone | [7] | ||
| Ribbon Creek Member | silty shale | [8] | ||
| Green Beds | glauconitic sandy mudstone, calcareous and phosphatic concretions | [9] | ||
| Grey Beds | ||||
| Gryphaea Bed | coquina with shells of Gryphaea impressimarginata, ammonites and belemnites; calcareous siltstone | [10] | ||
| Corbula munda Beds | silty shale, calcareous sandstone | [11] | ||
| Pigeon Creek Member | calcareous siltstone and grey shale | [12] | ||
| Highwood Member | dark grey shale, bioturbated sandstone | [13] | ||
| Rock Creek Member | also called "Belemnite zone" - fine-grained grey sandstone that may contain commercial gas reserves | [14] | ||
| Lille Member | coquina with Gryphaea and Ostrea shells | [15] | ||
| fissile black calcareous shale, thin-bedded black argillaceous limestone | [16] | |||
| Red Deer Member | black shale, black laminated limestone | [17] | ||
| Oxytoma Bed | coquina with Oxytoma shells | [18] | ||
| Nordegg Member | dark cherty and phosphatic limestone, calcareous shale | [19] | ||