{{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 [[Volcanism of the Mount Edziza volcanic complex#Little Iskut eruptive period|Little Iskut eruptive period]] | 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, 47, 61, 63, 246, 249, 267|isbn=0-660-14407-7|doi=10.4095/133497|doi-access=free}}</ref> | age = {{Fossil range|7.2}} | period = Miocene | prilithology = [[Trachybasalt]]<ref name="Souther"/> | otherlithology = | namedfor = [[Little Iskut River]]<ref name="Souther"/> | namedby = [[Jack Souther|Souther]] ''et al.''<ref name="LCGU">{{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}}</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 = Upper Little Iskut<ref name="Souther"/><br>Lower Little Iskut<ref name="Souther"/> | underlies = [[Armadillo Formation]]<ref name="Souther"/><br>[[Nido Formation]]<ref name="Souther"/> | overlies = [[Raspberry Formation]]<ref name="Souther"/> | 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]].<ref name="Souther"/><ref>{{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}}</ref>
==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.<ref name="Souther"/><ref name="Edwards"/> 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.<ref name="Souther"/>
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.<ref name="Souther"/>
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.<ref name="Souther"/>
[[K–Ar dating]] has yielded an age of 7.2 ± 0.3 million years for Little Iskut trachybasalt.<ref name="Souther"/>
==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 shield volcanoes]] [[Category:Shield volcanoes of Canada]]