Mount Cap Formation | |
---|---|
Stratigraphic range: Cambrian | |
Type | Formation |
Lithology | |
Primary | Shale, siltstone |
Other | Sandstone |
Location | |
Coordinates | 63°24′23″N123°12′22″W / 63.40639°N 123.20611°W |
Region | Northwest Territories |
Country | Canada |
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 100 to 300 metres (330 to 980 ft), 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,[ dubious – discuss ] 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]