{{Short description|Geological formation in British Columbia}} {{Infobox Rockunit | name = Armadillo Formation | image = File:Edziza042909-- 040-7.jpg | caption = [[Basalt]]ic lava flows of the Armadillo Formation are exposed in [[Sezill Creek]] valley | type = [[Geological formation]]<ref name="Souther">{{Cite report|last1=Souther|first1=J. G.|author-link1=Jack Souther|title=The Late Cenozoic Mount Edziza Volcanic Complex, British Columbia|work=[[Geological Survey of Canada]]|publisher=Canada Communication Group|series=Memoir 420|year=1992|pages=32, 61, 71, 246, 267|isbn=0-660-14407-7|doi=10.4095/133497|doi-access=free}}</ref> | age = {{Fossil range|6.9|6.1}} | period = Miocene | prilithology = [[Alkali basalt]], [[comendite]], [[trachyte]]<ref name="Souther"/> | otherlithology = | namedfor = [[Armadillo Peak]]<ref name="Souther"/> | namedby = [[Jack Souther|Souther]] ''et al.''<ref name="LCGU">{{cite web|url=https://weblex.canada.ca/html/000000/GSCC00053000458.html|title=Armadillo Formation|work=[[Lexicon of Canadian Geologic Units]]|publisher=[[Government of Canada]]|access-date=2023-08-04}}</ref> | year_ts = 1984<ref name="LCGU"/> | region = [[British Columbia]]<ref name="Souther"/> | country = Canada<ref name="Souther"/> | coordinates = {{coord|57.5|N|130.6|W|display=inline,title}}<ref name="Edwards">{{cite thesis|last1=Edwards|first1=Benjamin Ralph|degree=PhD|title=Field, kinetic, and thermodynamic studies of magmatic assimilation in the Northern Cordilleran Volcanic Province, northwestern British Columbia|publisher=[[University of British Columbia]]|year=1997|page=10|isbn=0-612-25005-9}}</ref> | unitof = [[Mount Edziza volcanic complex]]<ref name="Edwards"/> | subunits = | underlies = [[Ice Peak Formation]], Spectrum Formation, [[Big Raven Formation]], [[Nido Formation]]<ref name="Souther"/> | overlies = [[Little Iskut Formation]], [[Raspberry Formation]]<ref name="Souther"/> | thickness = | extent = | area = | map = File:Armadillo Formation.png | map_caption = [[Paleogeological]] map showing the inferred maximum extent of the Armadillo Formation at the end of the [[Volcanism of the Mount Edziza volcanic complex#Armadillo eruptive period|Armadillo eruptive period]] }} The '''Armadillo Formation''' is a [[stratigraphic unit]] of [[Miocene]] age in northwestern [[British Columbia]], Canada.
==Name== The Armadillo Formation takes its name from [[Armadillo Peak]], a volcanic peak east of [[Raspberry Pass]] in the middle of the [[Mount Edziza volcanic complex]].<ref name="Souther"/><ref>{{cite bcgnis|id=2478|name=Little Iskut River|archive-url=https://web.archive.org/web/20210930231839/https://apps.gov.bc.ca/pub/bcgnws/names/9205.html|archive-date=2021-09-30|access-date=2023-06-28}}</ref>
==Geology== The Armadillo Formation has a volume of {{Convert|159|km3|mi3|abbr=on}}, making it the most voluminous of the 13 [[geological formation]]s comprising the Mount Edziza volcanic complex.<ref name="Edwards"/> It [[conformably]] overlies the [[Little Iskut Formation]], as well as the [[Raspberry Formation]]. It is overlain by the [[Ice Peak Formation]], [[Nido Formation]], Spectrum Formation and [[Big Raven Formation]].<ref name="Souther"/>
The Armadillo Formation consists of [[volcanic rock]]s of both [[felsic]] and [[mafic]] compositions. They are the products of a long period of [[bimodal volcanism]], having issued from multiple eruptive centres. The felsic rocks include [[trachyte]] and [[comenditic]] [[rhyolite]] which form [[Pyroclastic rock|pyroclastic]] deposits, [[lava dome]]s and lava flows. [[Basalt]] is the main mafic rock of the Armadillo Formation and forms lava flows.<ref name="Souther"/>
[[K–Ar dating]] of the Armadillo Formation has yielded ages of 10.2 ± 1.4 million years for comendite, 6.9 ± 0.3 million years and 6.1 ± 0.1 million years for comenditic [[ash flow]]s, 6.9 ± 0.3 million years for comenditic [[volcanic glass|glass]] and 6.5 ± 0.2 million years, 6.3 ± 0.5 million years, 6.2 ± 0.1 million years and 6.1 ± 0.2 million years for [[hawaiite]].<ref name="Souther"/> The first age is anomalously old and most likely results from excessive atmospheric [[argon]].<ref name="LCGU"/>
==See also== *[[Volcanism of the Mount Edziza volcanic complex]]
==References== {{reflist}}
{{Mount Edziza volcanic complex}}
[[Category:Geologic formations of the Mount Edziza volcanic complex]] [[Category:Miocene British Columbia]] [[Category:Miocene volcanism]] [[Category:Basalt formations]] [[Category:Rhyolite formations]] [[Category:Trachyte formations]]