Mount Cap formation
Encyclopedia
The Mount Cap formation is a geological unit exposed in the Mackenzie Mountains, northern Canada. It was deposited in a shallow shelf setting in the late Early Cambrian, and contains an array of Burgess Shale
-type microfossils that have ben recovered by acid maceration
.
The formation is one to three hundred metres thick, and comprises shales, silt- and sand-stones with a high glauconite
content. It has been exposed to remarkably little metamorphic activity given its great age; it is dated to the Bonnia–Olenellus
Trilobite Zone
. 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, 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. 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.
Burgess Shale
The Burgess Shale Formation, located in the Canadian Rockies of British Columbia, is one of the world's most celebrated fossil fields, and the best of its kind. It is famous for the exceptional preservation of the soft parts of its fossils...
-type microfossils that have ben recovered by acid maceration
Acid maceration
Acid maceration is a technique to extract organic microfossils from a surrounding rock matrix using acid.Hydrochloric acid or acetic acid may be used to extract phosphatic fossils, such as the small shelly fossils, from a carbonate matrix....
.
The formation is one to three hundred metres thick, and comprises shales, silt- and sand-stones with a high glauconite
Glauconite
Glauconite is an iron potassium phyllosilicate mineral of characteristic green color with very low weathering resistance and very friable.It crystallizes with a monoclinic geometry...
content. It has been exposed to remarkably little metamorphic activity given its great age; it is dated to the Bonnia–Olenellus
Olenellus
Olenellus is a genus of trilobite that lived during the Early Cambrian. It is commonly found in areas of Europe and North America...
Trilobite Zone
Trilobite zone
Trilobites are used as index fossils to subdivide the Cambrian period. Assemblages of trilobites define trilobite zones. The Olenellus zone has traditionally marked the top of the Lower Cambrian, and is followed by the Eokochaspis zone....
. 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, 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. 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.