A new method to evaluate the power ratio distributions of astronomical signals: A case study from Upper Cretaceous terrestrial sediments.

Astronomical cycles reliably identified in the sedimentary record are useful for their paleoclimatic interpretations and construction of astrochronology. However, the depositional response and burial-diagenesis processes play a crucial role in distorting the time scales of geological records and introducing noise to orbital signals. How to evaluate the response of varied depositional environments to astronomical forcing remains a challenge. We developed the random-length average orbital power ratio calculation (RAOPR) method to evaluate average orbital power ratio distributions within a specific time interval and applied this new method to the theoretical eccentricity-tilt-precession (ETP) plus noise series and an astronomically tuned Cretaceous terrestrial stratigraphic record spanning ~24 m.y. (92-65 Ma, except for an ~3.8 m.y. gap from ca. 79.9 Ma to 76.1 Ma). Using the merged ETP plus noise series, we observed different orbital power ratio distributions for different background noise intervals. For the Cretaceous terrestrial Songliao Basin, we retrieved long-term orbital variations and used the RAOPR method to calculate the average orbital power ratios in different depositional environment intervals. Our results suggest that unusually high precession power in the Yaojia Formation resulted, in part, from autogenic processes, and unusually low precession power in the Nenjiang Formation can be attributed to marine incursion events. The eccentricity power of the meandering river facies was much higher than observed in other facies intervals. Conversely, the lowest precession power in the meandering facies may be attributed, in part, to the erosion "clipping" effect, which decreases the high-frequency precession band power and increases low-frequency eccentricity band power. [ABSTRACT FROM AUTHOR]