Comment on “Geologic evidence for chaotic behavior of the planets and its constraints on the third-order eustatic sequences at the end of the Late Paleozoic Ice Age” by Fang, Q., Wu, H., Hinnov, L. A., Jing, X., Wang, X., & Jiang, Q. [Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 440, 15 December 2015, 848–859 (2015)]

Abstract Fang et al. (2015: Geologic evidence for chaotic behavior of the planets and its constraints on the third-order eustatic sequences at the end of the Late Paleozoic Ice Age) claim to have identified a comprehensive suite of orbital periodicities (Milankovitch cycles) in a Permian succession in southern China through the use of spectral analysis. We refute their claim on the grounds that their spectral analytic method – specifically, the estimation of significance thresholds – greatly overestimates the significance of the periodicities. We show that the same method, implemented in the same software package, yields ‘significant’ cycle periods in purely random, synthesised data. In an earlier paper, we warned that the cyclostratigraphic community is generating large numbers of similarly false claims of orbital periodicities in stratigraphic data by making the same mistakes as Fang et al. We urge greater awareness of this problem among editors, reviewers, readers and users of the cyclostratigraphic literature. Further, all cyclostratigraphic conclusions dependent on the results of this kind of spectral analysis, including but not restricted to astrochronological timescale calibrations, should be regarded with suspicion unless confirmed by more rigorous methods.