Middle Pleistocene age of the Nome River glaciation, northwestern Alaska

Darrell S Kaufman, Robert C. Walter, Julie Brigham-Grette, David M. Hopkins

Research output: Contribution to journalArticle

20 Citations (Scopus)

Abstract

During the middle Pleistocene Nome River glaciation of northwestern Alaska, glaciers covered an area an order of magnitude more extensive than during any subsequent glacial intervals. The age of the Nome River glaciation is constrained by laser-fusion 40Ar 39Ar analyses of basaltic lava that overlies Nome River drift at Minnie Creek, central Seward Peninsula, that average 470,000 ± 190,000 yr (±1σ). Milligram-size subsamples of the lava were dated to identify and eliminate extraneous 40Ar enrichments that rendered the mean of conventional KAr dates on larger bulk samples of the same flow too old (700,000 ± 570,000 yr). While the 40Ar 39Ar analyses provide a minimum limiting age for the Nome River glaciation, maximum ages are provided by a provisional KAr date on a basaltic lava flow that underlies the Nome River drift at nearby Lave Creek, by paleomagnetic determinations of the drift itself at and near the type locality, and by amino acid epimerization analysis of molluscan fossils from nearshore sediments of the Anvilian marine transgression that underlie Nome River drift on the coastal plain at Nome. Taken together, the new age data indicate that the glaciation took place between 580,000 and 280,000 yr ago. The altitude of the Anvilian deposits suggests that eustatic sea level during the Anvilian transgression rose at least as high as and probably higher than during the last interglacial transgression; by correlation with the marine oxygen-isotope record, the transgression probably dates to stage 11 at 410,000 yr, and the Nome River glaciation is younger still. Analyses of floor altitudes of presumed Nome River cirques indicate that the Nome River regional snowline depression was at least twice that of the maximum late Wisconsin. The cause of the enhanced snowline lowering appears to be related to greater availability of moisture in northwestern Alaska during the middle Pleistocene.

Original languageEnglish (US)
Pages (from-to)277-293
Number of pages17
JournalQuaternary Research
Volume36
Issue number3
DOIs
StatePublished - 1991
Externally publishedYes

Fingerprint

glaciation
Pleistocene
river
transgression
snowline
lava
Middle Pleistocene
Transgression
Last Interglacial
type locality
lava flow
coastal plain
oxygen isotope
glacier
amino acid
laser
moisture
sea level
fossil
Creek

ASJC Scopus subject areas

  • Earth and Planetary Sciences(all)
  • Earth-Surface Processes

Cite this

Middle Pleistocene age of the Nome River glaciation, northwestern Alaska. / Kaufman, Darrell S; Walter, Robert C.; Brigham-Grette, Julie; Hopkins, David M.

In: Quaternary Research, Vol. 36, No. 3, 1991, p. 277-293.

Research output: Contribution to journalArticle

Kaufman, Darrell S ; Walter, Robert C. ; Brigham-Grette, Julie ; Hopkins, David M. / Middle Pleistocene age of the Nome River glaciation, northwestern Alaska. In: Quaternary Research. 1991 ; Vol. 36, No. 3. pp. 277-293.
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