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The geologic record of Milankovitch climate cycles provides a rich
conceptual and temporal framework for evaluating Earth system
evolution, bestowing a sharp lens through which to view our
planet’s history. However, the utility of these cycles for constraining
the early Earth system is hindered by seemingly insurmountable
uncertainties in our knowledge of solar system behavior
(including Earth–Moon history), and poor temporal control for validation
of cycle periods (e.g., from radioisotopic dates). Here we
address these problems using a Bayesian inversion approach to
quantitatively link astronomical theory with geologic observation,
allowing a reconstruction of Proterozoic astronomical cycles, fundamental
frequencies of the solar system, the precession constant,
and the underlying geologic timescale, directly from stratigraphic
data. Application of the approach to 1.4billionyearold rhythmites
indicates a precession constant of 85.79 ± 2.72 arcsec/year (2σ),
an Earth–Moon distance of 340,900 ± 2,600 km (2σ), and length of
day of 18.68 ± 0.25 hours (2σ), with dominant climatic precession
cycles of ∼14 ky and eccentricity cycles of ∼131 ky. The results
confirm reduced tidal dissipation in the Proterozoic. A complementary
analysis of Eocene rhythmites (∼55 Ma) illustrates how the
approach offers a means to map out ancient solar system behavior
and Earth–Moon history using the geologic archive. The method
also provides robust quantitative uncertainties on the eccentricity
and climatic precession periods, and derived astronomical timescales.
As a consequence, the temporal resolution of ancient Earth
system processes is enhanced, and our knowledge of early solar
system dynamics is greatly improved.
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