Whole-rock K-Ar age for a basaltic andesite from the Uegusukudake Formation in Kume-jima, Central Ryukyu Arc

Hiroshi Kitagawa, Ryuichi Shinjo

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

Whole-rock K-Ar dating for a basaltic andesite lava from the Uegusukudake Formation in Kume-jima, Central Ryukyu Arc, yields age of 2.13±0.19 Ma. The sample dated is from the middle horizon of the Formation. This age is compatible with recently published K-Ar ages of 2.76±0.48 and 2.24±0.10 Ma for a picrite basalt from the lowest part and an andesite from the upper part of the Formation, respectively. The age, however, is inconsistent with the previously reported K-Ar ages of 5.5 and 4.6 Ma. The result is also concordant with ages estimated from Sr isotopic ratios for molluscan fossils (~3.2−3.1 Ma) for the Aka Formation underlying the Uegusukudake Formation. This result suggests that tholeiitic basalts and basaltic andesites erupted after the eruption of picrite basalts with a short time interval at the late Pliocene.

Original languageEnglish
Pages (from-to)237-240
Number of pages4
JournalJapanese Magazine of Mineralogical and Petrological Sciences
Volume30
Issue number5
DOIs
Publication statusPublished - Jan 1 2001
Externally publishedYes

Keywords

  • Basaltic andesite
  • K-Ar dating
  • Kume -jima
  • Picrite basalt
  • Pliocene
  • Ryukyu Arc
  • Uegusukudake Formation

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Economic Geology

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