Articles | Volume 20, issue 24
Research article
19 Dec 2023
Research article |  | 19 Dec 2023

Revisiting the applicability and constraints of molybdenum- and uranium-based paleo redox proxies: comparing two contrasting sill fjords

K. Mareike Paul, Martijn Hermans, Sami A. Jokinen, Inda Brinkmann, Helena L. Filipsson, and Tom Jilbert

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Cited articles

Adelson, J. M., Helz, G. R., and Miller, C. V.: Reconstructing the rise of recent coastal anoxia; molybdenum in Chesapeake Bay sediments, Geochim. Cosmochim. Ac., 65, 237–252,, 2001. 
Aksnes, D. L., Aure, J., Johansen, P. O., Johnsen, G. H., and Salvanes, A. G. V.: Multi-decadal warming of Atlantic water and associated decline of dissolved oxygen in a deep fjord, Estuar. Coast. Shelf. S., 228, 106392,, 2019. 
Alessi, D. S., Lezama-Pacheco, J. S., Stubbs, J. E., Janousch, M., Bargar, J. R., Persson, P., and Bernier-Latmani, R.: The product of microbial uranium reduction includes multiple species with U(IV)-phosphate coordination, Geochim. Cosmochim. Ac., 131, 115–127,, 2014. 
Alessi, D. S., Uster, B., Veeramani, H., Suvorova, E. I., Lezama-Pacheco, J. S., Stubbs, J. E., Bargar, J. R., and Bernier-Latmani, R.: Quantitative separation of monomeric U(IV) from UO2 in products of U(VI) reduction, Environ. Sci. Technol., 46, 6150–6157,, 2012. 
Algeo, T. J. and Li, C.: Redox classification and calibration of redox thresholds in sedimentary systems, Geochim. Cosmochim. Ac., 287, 8–26,, 2020. 
Short summary
Seawater naturally contains trace metals such as Mo and U, which accumulate under low oxygen conditions on the seafloor. Previous studies have used sediment Mo and U contents as an archive of changing oxygen concentrations in coastal waters. Here we show that in fjords the use of Mo and U for this purpose may be impaired by additional processes. Our findings have implications for the reliable use of Mo and U to reconstruct oxygen changes in fjords.
Final-revised paper