AstroGeoFit in action. Towards an Eccentricity-Based Astronomical Time Scale for 40–100 Ma

Changes in Earth’s orbit and axial tilt affect the distribution of solar radiation across the planet’s surface, influencing climate and leaving recognizable imprints in sedimentary layers over time. These recurring patterns, known as Milankovitch cycles, arise from gravitational interactions with other bodies in the Solar System. Their preservation in stratigraphic records allows the construction of continuous and precise age–depth models based on astronomical orbital cycles, helping to compensate for the discontinuities and uncertainties associated with other absolute dating methods.

In this study, we examine several tens of stratigraphic records spanning 40–100 Ma to establish and refine astronomical time scales by extracting signals related to Earth’s orbital eccentricity. We apply our newly released tool, AstroGeoFit (https://www.astrogeo.eu/astrogeofit/), which accommodates flexible time-varying sedimentation rates within stratigraphic sequences and quantifies associated uncertainties by combining genetic algorithm optimization with Bayesian approaches.

Beyond improving age–depth models at the scale of individual sections or cores, our results contribute towards a more systematic reconstruction of Earth’s eccentricity evolution from 40 to 100 Ma, derived primarily from stratigraphic records, providing intrinsic geological insights into the behavior of planetary orbits in deep time.