Spectral Analysis of Carboniferous Rhythmites Indicates Tidal Modulation and Marine Connectivity in the Cumberland Basin (Joggins Formation, Atlantic Canada)

ABSTRACT

The Joggins Formation of the Cumberland Basin preserves rhythmically laminated heterolithic strata that have been interpreted as evidence of marine influence during Late Pennsylvanian deposition. However, the persistence and nature of hydraulic connectivity into the basin remain uncertain. This study examines three rhythmite‐bearing intervals (R1–R3) using lamina‐thickness measurements combined with Fast Fourier Transform (FFT), Maximum Entropy Method (MEM), Continuous Wavelet Transform (CWT), Singular Spectrum Analysis (SSA), band‐pass filtering, and Monte Carlo significance testing against white‐noise and AR(1) red‐noise null models. The datasets contain statistically significant cyclicity expressed at multiple scales, although the strength of the signal varies among intervals. R3 exhibits the strongest evidence for persistent hierarchical cyclicity, R1 preserves a weaker but reproducible signal, and R2 records a more limited expression because of its shorter stratigraphic extent. Cyclic components identified independently through FFT, MEM, CWT, SSA, and band‐pass filtering exceed 95% significance thresholds and are unlikely to represent stochastic variability. Although the observed periodicities cannot be uniquely assigned to specific tidal constituents, their hierarchical organisation is consistent with tidal modulation and difficult to reconcile with alternative depositional mechanisms. The results provide quantitative evidence that tidal energy reached portions of the Cumberland Basin during deposition of the Joggins Formation and support paleogeographic models permitting marine connectivity into the basin, while not uniquely constraining the geometry or continuity of the marine pathway.