{{Short description|Geological formation in British Columbia}} {{Infobox Rockunit | name = Klastline Formation | image = File:Klastline Formation cones.jpg | caption = Glacially modified pyroclastic cones of the Klastline Formation | 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=22, 28, 191, 246, 267|isbn=0-660-14407-7|doi=10.4095/133497|doi-access=free}}</ref> | age = [[Pleistocene]]<br/>{{Fossil range|0.774|0.118}} | period = Pleistocene | prilithology = [[Alkali basalt]]<ref name="Souther"/> | namedfor = [[Klastline River]]<ref name="Souther"/> | namedby = [[Jack Souther|Souther]] ''et al.''<ref name="LCGU">{{cite web|url=https://weblex.canada.ca/html/007000/GSCC00053007723.html|title=Klastline Formation|work=[[Lexicon of Canadian Geologic Units]]|publisher=[[Government of Canada]]|access-date=2023-09-21}}</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 = Junction Member, Village Member<ref name="Spooner">{{cite journal|last1=Spooner|first1=Ian S.|last2=Osborn|first2=Gerald D.|last3=Barendregt|first3=R.|last4=Irving|first4=E.|url=http://www.acadiau.ca/~ispooner/pdfs_of_papers/Stikine%20River%20PAleomag%20Paper%20CJES.pdf|title=A Middle Pleistocene (isotope stage 10) glacial sequence in the Stikine River valley, British Columbia|journal=[[Canadian Journal of Earth Sciences]]|publisher=[[NRC Research Press]]|pages=1429−1431|volume=33|year=1996|issue=10|doi=10.1139/e96-107|bibcode=1996CaJES..33.1428S|access-date=2023-09-20|archive-date=2025-01-21|archive-url=https://web.archive.org/web/20250121124101/http://www.acadiau.ca/~ispooner/pdfs_of_papers/Stikine%20River%20PAleomag%20Paper%20CJES.pdf|url-status=dead}}</ref> | underlies = [[Big Raven Formation]]<ref name="LCGU"/> | overlies = [[Edziza Formation]]<ref name="LCGU"/> | thickness = | extent = | area = | map = | map_caption = }}
The '''Klastline Formation''' is a [[stratigraphic unit]] of [[Pleistocene]] age in northwestern [[British Columbia]], Canada.
==Description== The Klastline Formation is part of the [[Mount Edziza volcanic complex]].<ref name="Souther"/> This is the second largest eruptive centre in the [[Northern Cordilleran Volcanic Province]], attaining a volume of {{Convert|670|km3|mi3|abbr=off}} and an area of {{Convert|1000|km2|mi2|abbr=off}}.<ref name="SL">{{cite journal|title=Distribution, nature, and origin of Neogene–Quaternary magmatism in the northern Cordilleran volcanic province, Canada|last1=Edwards|first1=Benjamin R.|last2=Russell|first2=James K.|journal=[[Geological Society of America Bulletin]]|publisher=[[Geological Society of America]]|page=1284|volume=112|issue=8|year=2000|issn=0016-7606|doi=10.1130/0016-7606(2000)112<1280:dnaoon>2.0.co;2|bibcode=2000GSAB..112.1280E }}</ref> It consists of [[shield volcano]]es, [[stratovolcano]]es, [[cinder cone]]s and [[lava dome]]s that have formed in the last 12 million years.<ref name="Souther"/><ref>{{cite gvp|vn=320060|vtab=Subfeatures|title=Edziza: Synonyms & Subfeatures|archive-date=2021-08-10|access-date=2023-09-07}}</ref>
The Klastline Formation was emplaced during the fourth magmatic cycle of the Mount Edziza volcanic complex.<ref name="Souther"/> It consists of [[volcanic rock]]s that were issued from at least three eruptive centres on the northern and eastern sides of the Mount Edziza volcanic complex which produced minor [[lava fountain]]s and small pyroclastic cones.<ref name="Souther"/><ref name="Spooner"/> Lava of the Klastline Formation temporarily blocked streams adjacent to the volcanic complex which resulted in the creation of [[lava dam]]med lakes.<ref name="Souther"/>
==Lithology== The Klastline Formation consists primarily of [[alkali basalt]] flows [[interbedded]] with sand and gravel.<ref name="Souther"/><ref name="Spooner"/> It contains two named subunits; the Village Member which consists of regular [[columnar basalt]] jointing, and the Junction Member which is characterized by swirly jointed basalt. A sedimentary sequence referred to as the Days Ranch Member is preserved between various remnants of the Village Member. It consists of well-sorted sand and gravel.<ref name="Spooner"/>
==Distribution== The Klastline Formation has a volume of {{Convert|5.4|km3|mi3|abbr=off}}, making it one of the least voluminous [[geological formation]]s of the Mount Edziza volcanic complex.<ref name="Souther"/><ref name="Edwards"/> It occurs along the valleys of [[Kakiddi Creek]] and the [[Klastline River]] where it forms isolated, usually flat-topped erosional remnants with {{Convert|6|to|12|m|ft|adj=on|abbr=off}} high [[escarpment]]s. [[Klastline Cone]] on the western side of Kakiddi Valley was the main source of the Klastline Valley flows. Remnants of Klastline Formation basalt flows south of [[Buckley Lake (British Columbia)|Buckley Lake]] form scattered [[outcrop]]s and likely issued from a low, grassy hill surrounded by younger [[Big Raven Formation]] basalt flows.<ref name="Souther"/> A {{Convert|55|km|mi|adj=mid|-long|abbr=off}} sequence of Klastline Formation basalt flows is exposed along the [[Stikine River]] downstream from the Klastline River confluence.<ref name="Spooner"/>
==Age== The Klastline Formation was probably deposited over a long period of eruptive activity during the [[Middle Pleistocene|Middle]] to [[Late Pleistocene]].<ref name="Spooner"/><ref>{{cite book|last1=Smellie|first1=John L.|last2=Edwards|first2=Benjamin R.|title=Glaciovolcanism on Earth and Mars: Products, Processes and Palaeoenvironmental Significance|publisher=[[Cambridge University Press]]|year=2016|page=44|isbn=978-1-107-03739-7}}</ref> [[K–Ar dating]] of a large remnant of Klastline Formation basalt in Klastline Valley has yielded an age of 0.62 ± 0.04 million years. This age is consistent with its [[stratigraphic]] position between the Edziza and Kakiddi formations, which have ages of 0.9 million years and 0.3 million years, respectively.<ref name="LCGU"/> A K–Ar date of 0.33 ± 0.03 million years has been obtained from the top of a Village Member basalt flow on the [[Tahltan River]], suggesting that Klastline [[volcanism]] may have been coeval with that of the Kakiddi Formation.<ref name="Spooner"/><ref name="LCGU"/> Village Member basalt about {{Convert|2|km|mi|abbr=off}} downstream from the mouth of the Tahltan River on the east bank of the Stikine River has yielded a similar [[Ar–Ar date]] of 0.30 ± 0.10 million years.<ref name="Spooner"/>
==See also== *[[Volcanism of the Mount Edziza volcanic complex]]
==References== {{reflist|30em}}
{{Mount Edziza volcanic complex}}
[[Category:Geologic formations of the Mount Edziza volcanic complex]] [[Category:Pleistocene British Columbia]] [[Category:Pleistocene volcanism]] [[Category:Basalt formations]] [[Category:Stikine River]]