Diagenetic reddening of Early Eocene paleosols on King George Island, Antarctica

The clustering, content, and distribution of hematites (finely dispersed on the groundmass; coating/replacing primary minerals and as mottles and/or nodules) rather than their crystal size were responsible for the color differences. These properties were likely the result of past pedogenesis processes (forming originally ferrihydrite) linked with paleodrainage conditions. Heating by the covering lava flow affected the magnetic properties of two profiles but without affecting their color. Taken together, all these results suggest that the burial reddening took place by dehydration and transformation of ferrihydrite to hematite. Our findings highlight the importance of detailed mineralogical analysis to identify iron oxides present in reddish paleosols because identification based solely on morphology (e.g. yellowish color, gradual horizon transitions) can lead to misinterpretation of paleoenvironmental conditions.