| Mount Cap Formation | |
| Type: | Formation |
| Age: | Cambrian |
| Period: | Cambrian |
| Prilithology: | Shale, siltstone |
| Otherlithology: | Sandstone |
| Region: | Northwest Territories |
| Coordinates: | 63.4064°N -123.2061°W |
The Mount Cap Formation is a geologic formation exposed in the Mackenzie Mountains, northern Canada. It was deposited in a shallow shelf setting in the late Early Cambrian,[1] and contains an array of Burgess Shale-type microfossils that have been recovered by acid maceration.[2]
The formation is 100mto300mm (300feetto1,000feetm), and comprises shales, siltstones and sandstones with a high glauconite content.[1] It has been exposed to remarkably little metamorphic activity given its great age; it is dated to the Bonnia - Olenellus Trilobite Zone.[1] This zone lies within the Lower Cambrian Waucoban stage in North America, which is equivalent to the Caerfai in Wales, and thus the Comley of England,[3] and has yet to be formally ratified. Nevertheless, this makes it just younger than the earliest trilobites, and thus the earliest known Burgess Shale-type deposit, though this is disputable when considering the age of Chengjiang County fauna. Its organic-walled fauna, known as the "Little Bear biota", includes both non-mineralized and originally-mineralized taxa, including hyolith and trilobite fragments, anomalocaridid claws, arthropod carapaces and brachiopods.[4]