Spectral analysis and modeling of microcyclostratigraphy in late Paleozoic glaciogenic rhythmites, Paraná Basin, Brazil

Abstract

We investigate the depositional time scale of lithological couplets (fine sandstone/siltstone–siltstone/mudstone) from two distinctive outcrops of Permo-Carboniferous glacial rhythmites in the Itarare Group (Parana Basin, Brazil). Resolving the fundamental issue of time scale for these rhythmites is important in light of recent evidence for paleosecular variation measured in these sequences. Spectral analysis and tuning of high-resolution gray scale scans of sediment core microstratigraphy, which comprises pervasive laminations, reveal a comparable spectral content at both localities, with a frequency suite interpreted as that of short-term climate variability of Recent and modern times. This evidence for decadal- to centennial-scale deposition of these lithological couplets is discussed in light of the ‘varvic’ character, i.e., annual time scale that was previously assumed for the rhythmites.