Paleoclimate
Foram grain boundaries can reset δ18O in ~100 years
Open access · cc by · source: Europe PMC
Oxygen exchanges along foraminifera nanocrystallite grain boundaries fast enough that even glassy tests can be isotopically biased.
Key findings
Over 1% of test oxygen exchanged in 54 days at 90 °C without texture change. Kinetics fit grain-boundary diffusion (~2.4% of oxygen in boundaries) far faster than abiotic calcite. Extrapolated to 0 °C, grain boundaries equilibrate with pore fluid in about 100 years, so glassy screening cannot guarantee a pristine paleotemperature.
Methodology
Authors incubated Ammonia tests in 18O-enriched artificial seawater at chemical equilibrium with calcite (30–190 °C, hours to weeks), compared oxidative vs non-oxidative cleaning, and used exchange kinetics plus ultrastructure to identify the diffusion path.
Limitations
Experiments use enriched 18O and elevated temperature; the exact bias in buried ocean sediments depends on pore-fluid δ18O and burial history. Grain-boundary widths in biominerals were assumed, not measured, and only Ammonia was incubated.
How this study connects
Role on claims
Each row is a claim on a concept or method page where this paper supports, challenges, or qualifies the statement. Roles are hand-checked — not a model guess.
Oxygen exchanges along foraminifera nanocrystallite grain boundaries fast enough that even glassy tests can be isotopically biased.
Evidence for the claim as stated.
Related papers in this topic
Same topic cluster — not a recommendation engine.