More Like this

1. The molecular-level diagenetic clock of sinking marine organic matter

   https://doi.org/10.1073/pnas.2504769122  

   Forrer, Heather J; Stukel, Michael R; McKenna, Amy M; Chen, Huan; Holt, Amy D; Kranz, Sven A; Spencer, Robert G_M (December 2025, Proceedings of the National Academy of Sciences)

   Thiemens, Mark (Ed.)

   The marine biological carbon pump is driven by sinking particulate organic matter (POM). Sinking speed and remineralization rate determine flux attenuation in the mesopelagic. Since the fate of all marine organic matter is either complete remineralization or transformation to more stable products, diagenetic modifications impact carbon dioxide sequestration time from the atmosphere. To investigate particle transformation at the molecular level, we characterize the water-extractable organic matter (WEOM) fraction of sinking particles from dominant biogeochemical environments using ultrahigh-resolution mass spectrometry. We find distinct, inverse associations in molecular-level nitrogen content and degree of transformation (i.e., “stability”) of organic matter across a productivity gradient from coastal upwelling to oligotrophic conditions. Nitrogen enrichment and low stability were observed at the coastal upwelling site and persisted to depths >400 m. Further, carbon flux is strongly correlated with the relative abundance of stable WEOM (“Island of Stability” molecular formulae) across productivity regimes and depth. This suggests emergent patterns in epi- and mesopelagic diagenesis, highlighting that the molecular composition of sinking organic matter exiting the euphotic zone varies more across regions than as a function of depth. This is attributed to highly variable sinking rates and the microbial diagenetic histories within the euphotic zone. The stability–flux relationship is considered a “diagenetic clock” relative to organic matter formation where the relative abundance of Island of Stability molecular formulae describes the degree of departure from the organic matter molecular-level composition at formation. This ubiquitous trajectory of the diagenetic clock further underpins a global ocean molecular signature of sinking POM. 

   more » « less
2. Formation of diagenetic siderite in modern ferruginous sediments

   https://doi.org/10.1130/G46100.1  

   Vuillemin, Aurèle; Wirth, Richard; Kemnitz, Helga; Schleicher, Anja M.; Friese, André; Bauer, Kohen W.; Simister, Rachel; Nomosatryo, Sulung; Ordoñez, Luis; Ariztegui, Daniel; et al (April 2019, Geology)
3. Mercury in archaeological human bone: biogenic or diagenetic?

   https://doi.org/10.1016/j.jas.2019.05.005  

   Emslie, Steven D.; Alderman, Audrey; McKenzie, Ashley; Brasso, Rebecka; Taylor, Alison R.; Molina Moreno, María; Cambra-Moo, Oscar; González Martín, Armando; Silva, Ana Maria; Valera, António; et al (August 2019, Journal of Archaeological Science)
4. Silicate Weathering and Diagenetic Reaction Balances in Deltaic Muds

   https://doi.org/10.2475/001c.134118  

   Trapp-Müller, Gerrit; Aller, Robert C; Sluijs, Appy; Middelburg, Jack J (January 2025, American Journal of Science)

   Reactions between terrigenous sediments, marine-biogenic substances and seawater modulate multiple biogeochemical cycles, but the dynamics and factors governing these reactions are poorly constrained. Deltaic mobile muds are a major sedimentary facies along river-dominated ocean margins through which most terrigenous sediment transits and mixes with marine-biogenic matter, representing efficient and globally significant batch reactors. Here, we present a process-based model that combines equilibrium aqueous chemistry with kinetic concepts from sediment biogeochemistry and mineral sciences to explore the solution-mediated interplay of organic and inorganic matter alteration in episodically reworked deltaic muds. The model reproduces observed diagenetic conditions and product suites over the seasonal timescales relevant to deltaic systems and indicates a systematic and dynamic coupling between the sedimentary cycles of H⁺, C, P, Fe, S, Si, Mg, K, and Ca. We used the model in combination with published field observations and concepts of authigenic mineral occurrences to develop a generalized explanatory framework for silicate weathering fluxes and diagenetic reaction balances in marine sediments. Diagenetic silicate weathering is represented by a continuum of reaction balances with acid (reverse) and alkaline (forward) endmembers that is moderated by sediment sources, which determine the sediment’s weatheringpotential, and depositional environments, which govern theexpressionof this potential. Reverse weathering dominates in seasonally reworked, low-latitude deltaic muds, where green clays form rapidly from lateritic river sediments and biogenic silica under suboxic conditions. High mineral precipitation rates and protracted sediment remobilization drive large solute fluxes from/to these sediments. Net forward silicate weathering becomes more likely under steady, sustained anoxic conditions, particularly in volcanically-influenced settings and at minimal pre-weathering of sediment sources. These results further our understanding of the role silicate weathering and marine sediments play in global biogeochemistry and Earth system evolution, and can aid targeted ‘enhanced weathering’ strategies to environmental governance. 

   more » « less
5. Regionally Correlated Oxygen and Carbon Isotope Zonation in Diagenetic Carbonates of the Bakken Formation

   https://doi.org/10.1016/j.chemgeo.2019.119327  

   Denny, Adam C.; Orland, Ian J.; Valley, John W. (January 2020, Chemical Geology)