Middle Triassic Cyclostratigraphic Records Reveal Modulation of Orbital-Scale Hydroclimate Variability by Global Warming

Repeated warming episodes over multimillion year (Myr) timescales profoundly influenced hydroclimates during the Triassic, but their effects on orbital-scale variability remain elusive. Here, we investigate the Middle Triassic terrestrial cyclostratigraphic records from the paleo-equatorial western Pangea and the northeastern Tethys. Multiproxy timeseries (rock color, gamma-ray, and geochemical proxies) suggest synchronous orbital-scale hydroclimate variability in both regions, with amplified magnitudes temporally coinciding with warming episodes indicated by δ¹⁸O records. Earth system modeling reproduces the amplification of orbitally forced hydroclimate variability in both regions under CO₂-induced warming, while revealing a globally heterogeneous response pattern. Consistent with Late Triassic records, these results demonstrate that Myr-scale warming cycles, rather than Myr-scale amplitude modulation of orbital parameters, directly modulated the magnitude of orbital-scale hydroclimate variability during the Triassic.