Original oxygen isotopic composition of planktic foraminifers preserved in diagenetically altered Pleistocene shallow-marine carbonates

S. Sakai, Akihiro Kano

Research output: Contribution to journalArticlepeer-review

9 Citations (Scopus)

Abstract

The original stable isotopic composition of low-Mg calcitic planktic foraminifer tests is preserved in Pleistocene shallow-marine carbonates (in the Ryukyu Group; Okinawa, Japan) that have been altered by meteoric diagenesis. Whole-rock analyses indicate depleted isotopic values for both δ13C (-1.9 to -5.4‰) and δ18O (-2.9 to -5.2‰), as well as carbonate mineralogy exclusively composed of low-Mg calcite. However, analysis of carefully-extracted planktic foraminifer tests (Globigerinoides sacculifer) that were separated from these whole-rock samples yield heavier δ13C values (-0.4 to 1.9‰) and δ18O values (-3.2 to -1.0‰). The foraminiferal values themselves and comparison of values of various components suggest that the low-Mg calcite tests preserve the original stable isotopic values. Subsequently, the downcore δ18O change of planktic foraminifers recorded in the Ryukyu Group results from middle Pleistocene glacial - interglacial change. By comparison, isotopic measurements based on whole-rock samples can be obtained diagenetic environmental signals, but misleading with regard to paleoclimatic inferences.

Original languageEnglish
Pages (from-to)197-204
Number of pages8
JournalMarine Geology
Volume172
Issue number3-4
DOIs
Publication statusPublished - Feb 15 2001

All Science Journal Classification (ASJC) codes

  • Oceanography
  • Geology
  • Geochemistry and Petrology

Fingerprint Dive into the research topics of 'Original oxygen isotopic composition of planktic foraminifers preserved in diagenetically altered Pleistocene shallow-marine carbonates'. Together they form a unique fingerprint.

Cite this