Orbital forcing in Lower Jurassic rhythmically bedded basinal carbonates: implications for depositional environment, benthic life, and stratigraphy

Abstract The Sinemurian to Pliensbachian limestone–marlstone succession exposed in the Tatra Mountains (Western Carpathians) forms part of a widespread, rhythmically bedded hemipelagic carbonate facies that developed along the north-western Tethyan margin. Such deposits are typical of marginal basins and are of particular interest due to their complex origin and well-developed cyclicity. The bulk carbonate δ 13 C record, integrated with numerically cross-checked alignment to Alpine reference sections (Tofino and Mt. Rettenstein) using dynamic time warping and a Bayesian framework, indicates that a 53 m-thick section spans the upper Obtusum Chronozone, the entire Oxynotum and Raricostatum chronozones, and the lowermost Jamesoni Chronozone (upper Sinemurian–lowermost Pliensbachian). This study focuses on the Lejowa Valley section, which represents the Fatricum Domain, a marginal basin of the north-western Tethyan margin, and integrates sedimentological, ichnological, and geochemical data with spectral analysis to evaluate the climatic and depositional controls on limestone–marlstone alternations and to assess the role of orbital forcing in their formation. Alternating marlstone- and limestone-dominated intervals reflect shifts in humidity and bottom-water ventilation: marlstone-rich intervals formed during more humid phases with reduced ventilation, whereas limestone-dominated intervals record drier conditions associated with better oxygenation. These patterns correspond to regional late Sinemurian climatic oscillations between warm–humid and semi-arid states. The preservation of trace fossils and the occurrence of primary lamination support a primary, depositional control on the limestone–marlstone alternation, rather than a diagenetic overprint. δ 13 C-based numerical correlation suggests a total duration of c. 2.3–2.7 Myr for the studied succession and an average sedimentation rate of c. 2.3 cm/kyr. Spectral analysis of bed-thickness variations reveals dominant periodicities at 1 m and 0.5 m wavelengths, interpreted as the expression of c. 40 kyr obliquity and c. 20 kyr precession cycles, respectively. The palaeolatitudinal position of the Fatricum Domain (~ 30°N) implies sensitivity to a monsoon-like atmospheric circulation, amplifying climate-driven sedimentary responses. Together, these results imply that the combined influence of obliquity and precession could control the Early Jurassic cyclic sedimentation pattern. The studied section can serve as a reference archive for orbitally forced palaeoclimate variability along the NW Tethyan margin.