%0 Journal Article
%T Climate control on banded iron formations linked to orbital eccentricity
%J -
%D 2019
%R https://doi.org/10.1038/s41561-019-0332-8
%X Astronomical forcing associated with Earth¡¯s orbital and inclination parameters (Milankovitch forcing) exerts a major control on climate as recorded in the sedimentary rock record, but its influence in deep time is largely unknown. Banded iron formations, iron-rich marine sediments older than 1.8 billion years, offer unique insight into the early Earth¡¯s environment. Their origin and distinctive layering have been explained by various mechanisms, including hydrothermal plume activity, the redox evolution of the oceans, microbial and diagenetic processes, sea-level fluctuations, and seasonal or tidal forcing. However, their potential link to past climate oscillations remains unexplored. Here we use cyclostratigraphic analysis combined with high-precision uranium¨Clead dating to investigate the potential influence of Milankovitch forcing on their deposition. Field exposures of the 2.48-billion-year-old Kuruman Banded Iron Formation reveal a well-defined hierarchical cycle pattern in the weathering profile that is laterally continuous over at least 250£¿km. The isotopic ages constrain the sedimentation rate at 10£¿m£¿Myr£¿1 and link the observed cycles to known eccentricity oscillations with periods of 405 thousand and about 1.4 to 1.6 million years. We conclude that long-period, Milankovitch-forced climate cycles exerted a primary control on large-scale compositional variations in banded iron formations
%U https://www.nature.com/articles/s41561-019-0332-8