stratigraphic unit
A stratigraphic unit is a volume of rock of identifiable origin and relative age range that is defined by the distinctive and dominant, easily mapped and recognizable petrographic, lithologic or paleontologic features ( facies) that characteriz ...
of
Neogene
The Neogene ( ,) is a geologic period and system that spans 20.45 million years from the end of the Paleogene Period million years ago ( Mya) to the beginning of the present Quaternary Period million years ago. It is the second period of th ...
age in northwestern
British Columbia
British Columbia is the westernmost Provinces and territories of Canada, province of Canada. Situated in the Pacific Northwest between the Pacific Ocean and the Rocky Mountains, the province has a diverse geography, with rugged landscapes that ...
, Canada.
Name
The Nido Formation takes its name from Nido Creek, a stream flowing northeast from the eastern flank of
Mount Edziza
Mount Edziza ( ; ) is a volcanic mountain in Cassiar Land District of northwestern British Columbia, Canada. It is located on the Big Raven Plateau of the Tahltan Highland which extends along the western side of the Stikine Plateau. Mount Ed ...
into Nuttlude Lake. Nido means "white man" in the
Tahltan language
Tahltan, Tāłtān, also called Tałtan ẕāke ("Tahltan people language"), dah dẕāhge ("our language") or didene keh ("this people’s way") is a poorly documented and endangered Northern Athabaskan language spoken by 235 of the Tahltan, Tah ...
.
Geology
The Nido Formation has a volume of , making it the second most voluminous
geological formation
A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics (lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock expo ...
of the
Mount Edziza volcanic complex
The Mount Edziza volcanic complex ( ; abbreviated MEVC) is a group of volcanoes and associated lava flows in northwestern British Columbia, Canada. Located on the Tahltan Highland, it is southeast of Telegraph Creek and southwest of Dease Lak ...
Raspberry
The raspberry is the edible fruit of several plant species in the genus ''Rubus'' of the Rosaceae, rose family, most of which are in the subgenus ''Rubus#Modern classification, Idaeobatus''. The name also applies to these plants themselves. Ras ...
, Armadillo and Little Iskut formations, all of which are
Miocene
The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...
in age. Also underlying the Nido Formation are pre-
Tertiary
Tertiary (from Latin, meaning 'third' or 'of the third degree/order..') may refer to:
* Tertiary period, an obsolete geologic period spanning from 66 to 2.6 million years ago
* Tertiary (chemistry), a term describing bonding patterns in organic ch ...
rocks of the
Stikinia
Stikinia, or the Stikine terrane, is a terrane in British Columbia, Canada; the largest of the Canadian Cordillera. It formed as an independent, intraoceanic volcanic arc during the Paleozoic and Mesozoic.
Stikinia forms the bedrock of numerous ...
terrane
In geology, a terrane (; in full, a tectonostratigraphic terrane) is a crust fragment formed on a tectonic plate (or broken off from it) and accreted or " sutured" to crust lying on another plate. The crustal block or fragment preserves its d ...
. Overlying the Nido Formation are the Spectrum,
Pyramid
A pyramid () is a structure whose visible surfaces are triangular in broad outline and converge toward the top, making the appearance roughly a pyramid in the geometric sense. The base of a pyramid can be of any polygon shape, such as trian ...
Pliocene
The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58
Two subunits comprise the Nido Formation, namely the Tenchen Member and the Kounugu Member. Both members are separated by the Armadillo Highlands in the middle of the Mount Edziza volcanic complex. The Tenchen Member forms a
lava field
A lava field, sometimes called a lava bed, is a large, mostly flat area of lava flows. Such features are generally composed of highly fluid basalt lava, and can extend for tens or hundreds of kilometers across the underlying terrain.
Morp ...
north of the Armadillo Highlands while the Kounugu Member forms a lava field south of the highlands.
The Nido Formation consists of
alkali basalt
Alkali basalt or alkali olivine basalt is a dark-colored, porphyritic volcanic rock usually found in oceanic and continental areas associated with volcanic activity, such as oceanic islands, continental rifts and volcanic fields. Alkali basalt i ...
and
hawaiite
Hawaiite is an olivine basalt with a composition between alkali basalt and mugearite. It was first used as a name for some lavas found on the island of Hawaii.
It occurs during the later stages of volcanic activity on oceanic islands such as Ha ...
lava flows that issued from multiple eruptive centres.
K–Ar dating
Potassium–argon dating, abbreviated K–Ar dating, is a radiometric dating method used in geochronology and archaeology. It is based on the measurement of the product of the radioactive decay of an isotope of potassium (K) into argon (Ar). Potas ...
has yielded ages of 7.8 ± 0.3 million years, 5.5 ± 1.6 million years, 4.5 ± 0.3 million years and 4.4 ± 0.5 million years for Nido alkali basalt.