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GEOREF RECORD

Holocene tephras in lake cores from northern British Columbia, Canada

Thomas R. Lakeman, John J. Clague, Brian Menounos, Gerald D. Osborn, Britta J. L. Jensen and Duane G. Froese
Holocene tephras in lake cores from northern British Columbia, Canada
Canadian Journal of Earth Sciences = Revue Canadienne des Sciences de la Terre (August 2008) 45 (8): 935-947

Abstract

Sediment cores recovered from alpine and subalpine lakes up to 250 km apart in northern British Columbia contain five previously unrecognized tephras. Two black phonolitic tephras, each 5-10 mm thick, occur within 2-4 cm of each other in basal sediments from seven lakes in the Finlay River-Dease Lake area. The upper and lower Finlay tephras are slightly older than 10 220-10 560 cal year B.P. and likely originate from two closely spaced eruptions of one or two large volcanoes in the northern Cordilleran volcanic province. The Finlay tephras occur at the transition between deglacial sediments and organic-rich postglacial mud in the lake cores and, therefore, closely delimit the termination of the Fraser Glaciation in northern British Columbia. Sediments in Bob Quinn Lake, which lies on the east edge of the northern Coast Mountains, contain two black tephras that differ in age and composition from the Finlay tephras. The lower Bob Quinn tephra is 3-4 mm thick, basaltic in composition, and is derived from an eruption in the Iskut River volcanic field about 9400 cal years ago. The upper Bob Quinn tephra is 12 mm thick, trachytic in composition, and probably 7000-8000 cal years old. A fifth tephra occurs as a cryptotephra near the top of two cores from the Finlay River area and is correlated to the east lobe of the White River tephra (ca. 1150 cal year B.P.). Although present throughout southern Yukon, the White River tephra has not previously been documented this far south in British Columbia. The tephras are valuable new isochrons for future paleoenvironmental studies in northern British Columbia.


ISSN: 0008-4077
EISSN: 1480-3313
Coden: CJESAP
Serial Title: Canadian Journal of Earth Sciences = Revue Canadienne des Sciences de la Terre
Serial Volume: 45
Serial Issue: 8
Title: Holocene tephras in lake cores from northern British Columbia, Canada
Affiliation: Simon Fraser University, Department of Earth Sciences, Burnaby, BC, Canada
Pages: 935-947
Published: 200808
Text Language: English
Summary Language: French
Publisher: National Research Council of Canada, Ottawa, ON, Canada
References: 42
Accession Number: 2009-006631
Categories: Quaternary geology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 4 tables, geol. sketch map
N56°00'00" - N59°00'00", W132°00'00" - W126°00'00"
Secondary Affiliation: University of Northern British Columbia, CAN, CanadaUniversity of Calgary, CAN, CanadaUniversity of Alberta, CAN, Canada
Country of Publication: Canada
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 200904
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