Milankovitch Cycles in Banded Iron Formations Constrain the Earth–Moon System 2.46 Billion Years Ago

Significance Milankovitch cycles recorded in 2.46-billion-year-old sediments indicate that Earth’s precession cycle had a significantly higher frequency than present, signaling shorter daylengths and Earth–Moon distance. This result is based on the number of precession-scale cycles per orbital eccentricity cycle identified in the strata, and provides the oldest reliable geological datum constraining past Earth–Moon dynamics. The differences between then and now are due to tidal dissipation, which, on Earth, takes place largely in the oceans. Reconstruction of the long-term evolution of the Earth–Moon system has been subject of theoretical studies, but geological confirmation has been lacking especially early in Earth’s history, where changes are most pronounced. Our study paves the way for future work bringing unprecedented insight into the Earth–Moon system history.