Figure 1: Schematic representation of redox zones and associated geochemical signals.
From: Low-oxygen waters limited habitable space for early animals
Generalized redox conditions across the Zaris Basin, Nama Group, during a highstand systems tract. Positive Ce anomalies form as Mn (oxyhydr)oxides dissolve in the manganous zone and Fe enrichments form under anoxic ferruginous conditions. Ten micromole is an estimate of O2 concentrations in the manganous zone, but overlying well-oxygenated waters probably contained higher O2 concentrations. Representative REY patterns, including positive Ce anomalies (magnitude in brackets), are shown for the Omkyk section in the Nama Group, alongside manganous zones from two modern environments25,27 (modern water column data plotted as [REY] × 106 for easy comparison with sedimentary [REY]).
