Navajo Sandstone concretions record extended magnetic chronology

Abstract

The study investigates iron oxide concretions from the Jurassic Navajo Sandstone in Utah to assess their potential as long-term paleomagnetic recorders. Using alternating field and thermal demagnetization, chemical analysis, and finite element magnetic modeling, the authors reveal multiple magnetic components within individual concretions. Their findings suggest a two-stage formation process involving initial iron hydroxide precipitation followed by progressive transformation to hematite, potentially recording ancient magnetic field fluctuations. The results have implications for understanding terrestrial concretion formation, marine ferromanganese nodules, and similar structures on Mars, such as the hematite-rich "blueberries" observed by the Opportunity rover.