Late Cenozoic geologic history and placer-gold distribution, Nome nearshore area, Alaska

Research output: Contribution to journalArticle

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Abstract

The spatial distribution of particulate gold in sediments blanketing the Nome nearshore area, Alaska, is the product of diverse late Cenozoic glacial, marine, fluvial, and deformational processes. Analysis of the extent of amino acid diagenesis in fossil molluscan shells from 51 boreholes drilled in 1967 by the U.S. Department of Interior in the Nome nearshore area demonstrates that the upper 20 m of the offshore deposits have been pervasively reworked. Below 20 m, sediments accumulated more continuously in a marine environment and contain minor amounts of particulate gold. The initiation of extensive reworking approximately coincides with the Beringian marine transgression (approximately 3.0 my), after which time glaciers advanced southward beyond the present-day coast and left deposits associated with the richest concentrations of particulate gold. Within the area extending approximately 5 km seaward of Nome, gold values in the top 20 m of sediment do not change seaward. The greatest concentrations are found within 4 m of the seafloor; lag-gravel deposits formed on till of the present seafloor are especially enriched. Although erosional surfaces analogous to the present seafloor may be buried within the sequence of Pliocene and Pleistocene deposits, the extent of the gold-bearing glacial deposits that would support these surfaces is not yet fully delineated. Reconstructions must take into account the possiblity that glaciers advanced onto the coastal plain during a period of high relative sea level. Coarse-grained, potentially gold-bearing debris would have been dispersed farther beyond a glacier terminating in a marine environment than from terrestrial-based ice. A better understanding of the geologic processes that formed the sedimentary sequence on- and offshore of Nome and consideration of theoretical constraints of placer-gold formation will lead to more reliable predictions of the distribution of particulate gold concentrations.

Original languageEnglish (US)
Pages (from-to)49-71
Number of pages23
JournalMarine Mining
Volume10
Issue number1
StatePublished - Jan 1991
Externally publishedYes

Fingerprint

Placers
gold
Gold
history
Deposits
Glaciers
Bearings (structural)
Sediments
glacier
seafloor
marine environment
sediment
distribution
Sea level
Gravel
glacial deposit
Boreholes
sedimentary sequence
reworking
Debris

ASJC Scopus subject areas

  • Engineering(all)
  • Earth and Planetary Sciences(all)
  • Environmental Science(all)

Cite this

Late Cenozoic geologic history and placer-gold distribution, Nome nearshore area, Alaska. / Kaufman, Darrell S.

In: Marine Mining, Vol. 10, No. 1, 01.1991, p. 49-71.

Research output: Contribution to journalArticle

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