Orbital Pacing of the TICE and Implications for the Onset of the Late Paleozoic Ice Age (lpia)

The Early Carboniferous is a key transition period toward the Late Paleozoic Ice Age. It is marked by major carbon isotope perturbations, including the Lower Alum Shale Event (LASE) and the Tournaisian Carbon. Isotope Excursion (TICE). The latter is commonly considered as a potential trigger for the onset of glaciationWhile recent studies have shown that orbital forcing, particularly long-term eccentricity modulation, influenced the timing of anoxic events in greenhouse climates such as the Devonian and Cretaceous, it remains unclear whether similar controls operated during this climatic transition. To investigate the potential role of orbital forcing on anoxia during the TICE interval, we conducted a cyclostratigraphic analysis of the Rivage section (Namur–Dinant Basin, Belgium), which exposes Early Tournaisian (Hastarian) deposits including the LASE and the onset of the TICE. High-resolution sampling (5 cm, locally 1 cm) provides a suitable record for this analysis. Cyclostratigraphic investigations were performed using Astrochron and WaverideR packages under R software, on XRF-derived Si/Al ratios, complemented by carbonate carbon isotope (d13C) measurements. The results reveal a clear 405-kyr eccentricity cyclicity in the Si/Al record, and astronomical tuning suggests that the studied interval spans approximately ~3.6 Myr, while the duration of the LASE was estimated at ~686 kyr. In addition, the orbital configuration preceding the TICE suggests the presence of a ~2.4-Myr Eccentricity node at the top of the section, just before or at the onset of the excursion. Together, these observations suggest a role of orbital forcing in pacing the timing of the TICE, in combination with other mechanisms, and therefore played a role in the broader climatic evolution toward the Late Paleozoic Ice Age.