Fig. 3.

Schematic model for the outwash of oxygenated basal meltwater to anoxic glaciomarine environments (not to scale). IFs deposited in ice-contact settings (within ∼2 km of the grounding line) are characterized by negative δ⁵⁶Fe values and may feature negative Ce anomalies and Mn-oxide enrichment, indicative of oxidizing conditions. Ice-proximal IFs (∼2 to 10 km from the grounding line) display predominantly positive δ⁵⁶Fe values and negligible to slight positive Ce anomalies. Ice-distal IFs (greater than ∼10 km from the grounding line) feature slight positive Ce anomalies and highly positive δ⁵⁶Fe values, with negligible Mn oxides. These geochemical trends are indicative of oxygenated glaciomarine environments which could have supported aerobic eukaryotes despite widespread anoxia during extreme glaciation. Microaerophilic Fe-oxidizing bacteria may have proliferated where O₂-bearing meltwater mixed with ferruginous seawater, potentially supporting heterotrophic food webs.