Unravelling Pre-Cenozoic Climate History: Astrochronology in the Western Canadian Sedimentary Basin

Geoscientists use the Earth's orbital parameters to calibrate geologic timescales with high precision. This project aims to reconstruct past climatic variations in the West Canadian Sedimentary Basin (WCSB) and contribute to a more nuanced comprehension of global climate processes.

The amount of solar insolation that reaches the Earth depends on the variations in planetary orbital parameters. However, it is not feasible to compute the orbital motion of the planets from their present state for the pre-Cenozoic geologic intervals because the solar system's orbital motions were chaotic before 60 Ma. At the same time, the outer solar planets behaved more regularly than the inner planets. The 405 kyr eccentricity cycle related to Jupiter and Venus was successfully used as a timekeeper over the entire Mesozoic Era and many Paleozoic intervals (Laskar et al., 2011; Boulila et al., 2018; Zeebe, 2023). Some recent studies validated that the other cycles, the 173 and 1200 kyr obliquity (Charbonnier et al., 2018; Qin et al., 2021; Cao et al., 2024), 200, 1600 and 2400 kyr eccentricity cycles (Fang et al., 2018; Hilgen et al., 2020; Qin et al., 2021; Zhang et al., 2022), and short precession (20 kyr) and obliquity (40 kyr) cycles, also demonstrated great potential in astrochronology (De Vleeschouwer et al., 2012; Zeeden et al., 2023). Cyclostratigraphy, the identification of these cycles in sedimentary records, is the most effective tool for astrochronological calibration of geological and climate events.

This research project utilizes a multidisciplinary approach, including magnetostratigraphy, paleoclimate proxies, and cyclostratigraphy, to perform the astrochronological calibration and paleoclimatic reconstructions in the Western Canadian Sedimentary Basin (WCSB). By harnessing data analysis techniques and fieldwork, this study will expand upon existing research in the WCSB. Magnetic susceptibility, detrital input proxies, resistivity and seismic velocity well-logs, and gamma spectrometry will be employed to refine astrochronological tools and climate variation records. Emphasis will be placed on extending the 405 kyr cycle calibration and exploring other length cycles. Identifying the orbital parameter variations in the WCSB sedimentary records sheds light on the past regional and global climate change and provides accurate dates of the geological events.

Our project will also contribute to developing the mathematical tools to extract the astronomical cycles from the climate proxy records. Often, non-linear sedimentation rates and various natural processes that contribute to the smearing of the original astronomically driven signal impose additional difficulties for the identification of the cycles (Borowiecki et al., 2023). Different manual and statistical methods exist for tuning the climate signal to a reference curve to produce a meaningful age model (Hinnov, 2018). Various numerical tools will be used to extract the cycles and statistically estimate their robustness. In addition to our own numerical tools discussed in the previous sections, we plan to use the available commonly used packages, including Astrochron and TimeOpt (Meyers, 2017) and the Bayesian inversion approach (Meyers, 2019; De Vleeschouwer and Parnell, 2014; Malinverno and Meyers, 2024) to evaluate values of the solar system's fundamental frequencies and sedimentation rates.

References

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Boulila, S., Vahlenkamp, M., De Vleeschouwer, D., Laskar, J., Yamamoto, Y., Pälike, H., Turner, S.K., Sexton, P.F., Westerhold, T. and Röhl, U., 2018. Towards a robust and consistent middle Eocene astronomical timescale. Earth and Planetary Science Letters, 486, 94-107.

Cao, Y., Zhang, R., Wang, S., Kravchinsky, V.A., Sagnotti, L., Ferraro, J.V., Wei, X., Xian, F., Yue, L. and Gong, H., 2024. Predominant orbital forcing on Asian hydroclimate linked with deep-sea records during the Miocene Climate Optimum. Submitted.

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