NDLI: Revisiting Glauconite Geochronology: Lessons Learned from In Situ Radiometric Dating of a Glauconite-Rich Cretaceous Shelfal Sequence

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Revisiting Glauconite Geochronology: Lessons Learned from In Situ Radiometric Dating of a Glauconite-Rich Cretaceous Shelfal Sequence

Content Provider	MDPI
Author	Stefan, Lӧhr Juraj, Farkaš Alice, Matsdotter Bäckström Scheiblhofer, Esther Moser, Ulrike Wilmsen, Markus Gallhofer, Daniela Zack, Thomas Baldermann, Andre
Copyright Year	2022
Description	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 glauconite 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 deconvolution 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 glauconite could be a suitable archive for paleo-environmental reconstructions and direct sediment dating.
Starting Page	818
e-ISSN	2075163X
DOI	10.3390/min12070818
Journal	Minerals
Issue Number	7
Volume Number	12
Language	English
Publisher	MDPI
Publisher Date	2022-06-27
Access Restriction	Open
Subject Keyword	Minerals Geology Glauconite Radiometric Dating in Situ Rb-sr Geochronology Diagenesis Illitization La-icp-ms/ms
Content Type	Text
Resource Type	Article

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