Description
The proposed project investigates the role of astronomical cycles (Milanković cycles) in the Paleoarchean, more than 3.2 billion years ago. It is based on newly available drill cores from the Moodies Hills Block (Agnes Gold Mine, South Africa), which were donated by the mining company and transferred to Münster. After completion of the analyses, they will be integrated into the ICDP-BASE core collection and curated together at the international core repository in Berlin-Spandau.
These cores represent some of the oldest preserved sedimentary successions on Earth. The project aims to describe their depositional environments and facies in detail, to generate high-resolution geochemical and mineralogical datasets, and to test for the presence of astronomically forced climate oscillations. Using X-ray fluorescence and hyperspectral techniques, proxies such as elemental ratios (e.g., Fe/Al, K/Al) and mineral phases will be measured. Statistical time-series analyses will be applied to detect periodic patterns and evaluate their consistency with Milanković cycles (eccentricity, obliquity, precession).
A central objective is to use these signals to constrain the Earth–Moon distance and the precession constant during the early Archean. This provides an independent approach to reconstructing Earth–Moon dynamics, complementary to previous tidalite-based methods. Direct comparison with results from the ICDP-BASE drill cores – in particular Site 5A – will allow for evaluating the robustness of astronomical signals across different depositional environments within the same basin.
In addition, the project will conduct a systematic search for potential spherule layers. Such impact ejecta deposits could serve as stratigraphic markers and provide new insights into the impact regime of the early Archean.
Overall, the project will contribute to a better understanding of the interactions between astronomical forcing, sedimentation, and climate under early Earth boundary conditions. It combines sedimentological, geochemical, and cyclostratigraphic approaches and strengthens international scientific use of the ICDP-BASE cores through the integration of the newly obtained Agnes cores.