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https://hdl.handle.net/2440/136268
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Type: | Journal article |
Title: | Revisiting Glauconite Geochronology: Lessons Learned from In Situ Radiometric Dating of a Glauconite-Rich Cretaceous Shelfal Sequence |
Author: | Scheiblhofer, E. Moser, U. Lӧhr, S. Wilmsen, M. Farkaš, J. Gallhofer, D. Bäckström, A.M. Zack, T. Baldermann, A. |
Citation: | Minerals, 2022; 12(7):818-1-818-19 |
Publisher: | MDPI AG |
Issue Date: | 2022 |
ISSN: | 2075-163X |
Statement of Responsibility: | Esther Scheiblhofer, Ulrike Moser, Stefan Löhr, Markus Wilmsen, Juraj Farkaš, Daniela Gallhofer, Alice Matsdotter Bäckström, Thomas Zack, and Andre Baldermann |
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 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. |
Keywords: | glauconite; radiometric dating; in situ Rb-Sr geochronology; diagenesis; illitization; LA-ICP-MS/MS |
Rights: | © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/) |
DOI: | 10.3390/min12070818 |
Grant ID: | http://purl.org/au-research/grants/arc/DP210100462 |
Published version: | http://dx.doi.org/10.3390/min12070818 |
Appears in Collections: | Earth and Environmental Sciences publications |
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hdl_136268.pdf | Published version | 25.67 MB | Adobe PDF | View/Open |
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