Modeled tephra ages from lake sediments, base of Redoubt Volcano, Alaska

Caleb J. Schiff, Darrell S Kaufman, Kristi L. Wallace, Al Werner, Teh Lung Ku, Thomas A. Brown

Research output: Contribution to journalArticle

12 Scopus citations

Abstract

A 5.6-m-long lake sediment core from Bear Lake, Alaska, located 22 km southeast of Redoubt Volcano, contains 67 tephra layers deposited over the last 8750 cal yr, comprising 15% of the total thickness of recovered sediment. Using 12 AMS 14C ages, along with the 137Cs and 210Pb activities of recent sediment, we evaluated different models to determine the age-depth relation of the core, and to determine the age of each tephra deposit. The selected age model is based on a mixed-effect regression that was passed through the adjusted tephra-free depth of each dated layer. The estimated age uncertainty of the 67 tephras averages ±105 yr (95% confidence intervals). Tephra-fall frequency at Bear Lake was among the highest during the past 500 yr, with eight tephras deposited compared to an average of 3.7/500 yr over the last 8500 yr. Other periods of increased tephra fall occurred 2500-3500, 4500-5000, and 7000-7500 cal yr. Our record suggests that Bear Lake experienced extended periods (1000-2000 yr) of increased tephra fall separated by shorter periods (500-1000 yr) of apparent quiescence. The Bear Lake sediment core affords the most comprehensive tephrochronology from the base of the Redoubt Volcano to date, with an average tephra-fall frequency of one every 130 yr.

Original languageEnglish (US)
Pages (from-to)56-67
Number of pages12
JournalQuaternary Geochronology
Volume3
Issue number1-2
DOIs
StatePublished - Feb 2008

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Keywords

  • Alaska
  • Cook inlet
  • Redoubt volcano
  • Tephra
  • Tephra-fall frequency
  • Tephrochronology
  • Volcanic hazards

ASJC Scopus subject areas

  • Geology
  • Earth and Planetary Sciences (miscellaneous)
  • Stratigraphy

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