Revisiting glauconite geochronology: lessons learned from in situ radiometric dating of a glauconite-rich cretaceous shelfal sequence

Esther Scheiblhofer, Ulrike Moser*, Stefan Lӧhr, Markus Wilmsen, Juraj Farkaš, Daniela Gallhofer, Alice Matsdotter Bäckström, Thomas Zack, Andre Baldermann

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    14 Citations (Scopus)
    62 Downloads (Pure)

    Abstract

    The 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 constraints 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.

    Original languageEnglish
    Article number818
    Pages (from-to)1-19
    Number of pages19
    JournalMinerals
    Volume12
    Issue number7
    DOIs
    Publication statusPublished - Jul 2022

    Bibliographical note

    Copyright the Author(s) 2022. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.

    Keywords

    • diagenesis
    • glauconite
    • illitization
    • in situ Rb-Sr geochronology
    • LA-ICP-MS/MS
    • radiometric dating

    Fingerprint

    Dive into the research topics of 'Revisiting glauconite geochronology: lessons learned from in situ radiometric dating of a glauconite-rich cretaceous shelfal sequence'. Together they form a unique fingerprint.

    Cite this