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  • Autor
    • Scheiblhofer, Esther
    • Moser, Ulrike
    • Lӧhr, Stefan
    • Wilmsen, Markus
    • Farkaš, Juraj
    • Gallhofer, Daniela
    • Matsdotter Bäckström, Alice
    • Zack, Thomas
    • Baldermann, Andre
  • TitelRevisiting Glauconite Geochronology: Lessons Learned from In Situ Radiometric Dating of a Glauconite-Rich Cretaceous Shelfal Sequence
  • Datei
  • DOI10.3390/min12070818
  • Erschienen inMaterials
  • Band12
  • Erscheinungsjahr2022
  • Heft7
  • LicenceCC BY 4.0
  • ISSN2075-163X
  • ZugriffsrechteCC-BY
  • Download Statistik15
  • Peer ReviewJa
  • AbstractThe scarcity of well-preserved and directly dateable sedimentary sequences is a major impediment to inferring the Earth’s paleo-environmental evolution. The authigenic mineral glau- conite can potentially provide absolute stratigraphic ages for sedimentary sequences and con- straints on paleo-depositional conditions. This requires improved approaches for measuring and interpreting glauconite formation ages. Here, glauconite from a Cretaceous shelfal sequence (Langenstein, northern Germany) was characterized using petrographical, geochemical (EMP), andmineralogical (XRD) screening methods before in situ Rb-Sr dating via LA-ICP-MS/MS. The obtained glauconite ages (~101 to 97 Ma) partly overlap with the depositional age of the Langenstein sequence (±3 Ma), but without the expected stratigraphic age progression, which we attribute to detrital and diagenetic illitic phase impurities inside the glauconites. Using a novel age deconvolu- tion approach, which combines the new Rb-Sr dataset with published K-Ar ages, we recalculate the glauconite bulk ages to obtain stratigraphically significant ‘pure’ glauconite ages (~100 to 96 Ma). Thus, our results show that pristine ages can be preserved in mineralogically complex glauconite grains even under burial diagenetic conditions (T < 65 °C; <1500 m depth), confirming that glauco- nite could be a suitable archive for paleo-environmental reconstructions and direct sediment dating.