Little Iskut Formation
{{Short description|Geological formation in British Columbia}}
{{Infobox Rockunit
| name = Little Iskut Formation
| image = File:Little Iskut Formation.png
| caption = Paleogeological map of the Little Iskut Formation at the end of the Little Iskut eruptive period
| type = Geological formation{{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, 47, 61, 63, 246, 249, 267|isbn=0-660-14407-7|doi=10.4095/133497|doi-access=free}}
| age = {{Fossil range|7.2}}
| period = Miocene
| prilithology = Trachybasalt
| otherlithology =
| namedfor = Little Iskut River
| namedby = Souther et al.{{cite web|url=https://weblex.canada.ca/html/008000/GSCC00053008550.html|title=Little Iskut Formation|work=Lexicon of Canadian Geologic Units|publisher=Government of Canada|access-date=2023-08-04}}
| region = British Columbia
| coordinates = {{coord|57.5|N|130.6|W|display=inline,title}}{{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}}
| unitof = Mount Edziza volcanic complex
| subunits = Upper Little Iskut
Lower Little Iskut
| underlies = Armadillo Formation
Nido Formation
| overlies = Raspberry Formation
| thickness =
| extent =
| area =
| map =
| map_caption =
}}
The Little Iskut Formation is a stratigraphic unit of Miocene age in northwestern British Columbia, Canada.
Naming
The Little Iskut Formation takes its name from the Little Iskut River, a tributary of the Iskut River which flows southeast from the southern end of the Mount Edziza volcanic complex.{{cite bcgnis|id=2478|name=Little Iskut River|archive-url=https://web.archive.org/web/20211024202848/https://apps.gov.bc.ca/pub/bcgnws/names/2478.html|archive-date=2021-10-24|access-date=2023-06-27}}
Geology
The Little Iskut Formation has a volume of {{Convert|14.6|km3|mi3|abbr=on}}, making it the seventh most voluminous geological formation comprising the Mount Edziza volcanic complex. It occurs at the northeastern end of the Spectrum Range where it covers a roughly {{Convert|10|km|mi|adj=mid|-wide|abbr=off}} area. A small portion of the Little Iskut Formation is exposed in the Mess Creek Escarpment to the west.
The Little Iskut Formation consists of trachybasalt flows and breccia. It ranges in thickness from {{Convert|90|m|ft|abbr=on}} on Stewpot Ridge to about {{Convert|300|m|ft|abbr=on}} near the middle of Artifact Ridge. The Little Iskut Formation originally formed a small symmetrical shield volcano during the Miocene.
The Little Iskut Formation conformably overlies the Raspberry Formation south of Bourgeaux Creek. Little Iskut trachybasalt is overlain by rhyolite of the Armadillo Formation and basalt of the Nido Formation. Two subunits comprise the Little Iskut Formation; the upper unit consists entirely of trachybasalt lava flows while the lower unit consists of abundant breccia.
K–Ar dating has yielded an age of 7.2 ± 0.3 million years for Little Iskut trachybasalt.
See also
References
{{reflist}}
{{Mount Edziza volcanic complex}}
Category:Geologic formations of the Mount Edziza volcanic complex