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Abstract The dynamical evolution of the solar system is chaotic with a Lyapunov time of only ∼5 Myr for the inner planets. Due to the chaos it is fundamentally impossible to accurately predict the solar system’s orbital evolution beyond ∼50 Myr based on present astronomical observations. We have recently developed a method to overcome the problem by using the geologic record to constrain astronomical solutions in the past. Our resulting optimal astronomical solution (called ZB18a) shows exceptional agreement with the geologic record to ∼58 Ma (Myr ago) and a characteristic resonance transition around 50 Ma. Here we show that ZB18a and integration of Earth’s and Mars’ spin vector based on ZB18a yield reduced variations in Earth’s and Mars’ orbital inclination and Earth’s obliquity (axial tilt) from ∼58 to ∼48 Ma—the latter being consistent with paleoclimate records. The changes in the obliquities have important implications for the climate histories of Earth and Mars. We provide a detailed analysis of solar system frequencies (gandsmodes) and show that the shifts in the variation in Earth’s and Mars’ orbital inclination and obliquity around 48 Ma are associated with the resonance transition and caused by changes in the contributions to the superposition ofsmodes, plusg–smode interactions in the inner solar system. Theg–smode interactions and the resonance transition (consistent with geologic data) are unequivocal manifestations of chaos. Dynamical chaos in the solar system hence not only affects its orbital properties but also the long-term evolution of planetary climate through eccentricity and the link between inclination and axial tilt.
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Testing Astronomical Solutions With Geological Data for the Latest Cretaceous: An Astronomically Tuned Time Scale
Abstract Astronomical solutions form the backbone of accurate dating for geology and paleoclimate studies. Beyond 50 Ma, however, the chaos inherent in the solar system makes it impossible to calculate a unique astronomical solution. Geological data have been used to constrain the chaos in order to arrive at an astronomically calibrated time scale up to the end‐Cretaceous. Here, we adopt and extend this approach into the latest Cretaceous, by re‐analyzing the Zumaia and Sopelana composite proxy records from the Maastrichtian. We find that the filtered total light reflectance () record is most compatible with the astronomical solution ZB20a. However, the results are sensitive to parameter choices in our algorithm, which we describe in detail. Nevertheless, we present evidence in favor of using solution ZB20a for cyclostratigraphic applications during the latest Cretaceous. Intervals with very long eccentricity nodes (VLNs) (low amplitude in the short eccentricity cycle) in the astronomical solutions that coincide with large amplitudes in the short eccentricity‐related peaks in the filtered proxy record rule out alternatives.
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- Award ID(s):
- 2034660
- PAR ID:
- 10578655
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Paleoceanography and Paleoclimatology
- Volume:
- 39
- Issue:
- 11
- ISSN:
- 2572-4517
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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