Extending the geological calibration of the geological time scale

Abstract

This thesis arises from the fact that changes in the geometry of the Earth-Sun system, due to the gravitational interaction among the planets, cause quasi-cyclic climatic variations that are imprinted in the geological record.
A speech-recognition method is adapted to provide an automated procedure to calibrate cyclic geological data to astronomical calculations. Synthetic data are used to test the performance of the new method. The new algorithm is then applied to lithological data. Results show that the method is well suited to objectively match geological data to astronomical calculations of the Earth’s orbit.
The calibration of the geological time scale is extended into the late Paleogene. This is achieved by generating a lithological proxy record employing an X-ray fluorescence Core Scanner that non-destructively determines elemental concentrations of calcium and iron on split sediment cores. These data exhibit cyclic variations that are shown to be of astronomical origin, and are then used to calibrate the relative duration of magnetochrons C16 through C18. Advanced time series analysis methods are used to extract the astronomical signal. It is shown that the most recent published astronomical solution is not compatible with geological data from the late Paleogene.
This new late Eocene time scale is independently confirmed by measurements of stable isotope ratios of oxygen and carbon, obtained from the same material, providing a high-resolution record of climatic variations over intervals of the late Middle and Late Eocene for the first time.
Astronomically calibrated geological data are analysed to extract parameters that are required for the calculation of detailed astronomical models. Very small changes in the precession constant of the Earth are extracted by developing a new interference method. This leads to the extraction of the long-term evolution of the tidal dissipation and dynamical ellipticity parameters of the Earth.
Geological data spanning the last ~37 million years are used to extract long term amplitude modulation patterns of the climatic signal. A comparison of the long term amplitude modulation derived from published astronomical calculations on the one hand, and those derived from a new calculation on the other hand (J. Laskar, 2001, unpublished) shows that the geological record supports the validity of the new solution. This study forms the basis for a further extension of the astronomical calibration of the geological time scale into earlier parts of the Paleogene.

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