Evaluation of the terrestrial sedimentary system response to astronomical forcing

When astronomical cycles can be reliably identified in the sedimentary record, they can provide a basis for paleoclimatic interpretations and the construction of an astrochronology. However, different paleoclimate proxies carry different astronomical-climatic-depositional information, which can display distinct orbital frequency features in strata. How to evaluate response of varied sedimentary environments to astronomical forcing remains a mystery. Here, we developed the Random-length Average Orbital Power Ratio calculation (RAOPR) method to evaluate the average power ratio distributions within a specific time interval. We have applied this new method to the theoretical eccentricity-tilt-precession (ETP) plus noise series and a ~24 million-year-long Cretaceous terrestrial stratigraphic record. From the merged ETP plus noise series and geological record, we observed different orbital signal component distributions. For the Cretaceous terrestrial Songliao Basin, we combined the integratePower method to retrieve the long-term orbital variations and used the RAOPR method to evaluate the orbital signal distribution in different lithological formations (or depositional environment intervals). We found that in different sedimentary environments, orbital signals show significant discrepancy both in magnitudes and ratios, indicating different depositional processes and local geological events have resulted in emergence, amplification, displacement and suppression of orbital frequency. Our study highlights the interaction between the external orbital forcing and internal climatic and/or depositional feedbacks and their influence on assessing the orbital signals from the stratigraphic successions.