- 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
- Download Statistik979
- 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.
[1.74 MB]