Impact of Cenozoic sea-level fluctuations on passive margin stratigraphic architecture: Implications for underground hydrogen storage potential

The global energy transition demands large-scale, long-duration storage, with underground hydrogen storage (UHS) in geological formations emerging as an important option. Passive continental margins host extensive Cenozoic successions that may represent significant UHS targets, yet predicting stratigraphic architecture in data-limited regions remains challenging. This study investigates whether the shift from low-frequency, low-amplitude to high-frequency, high-amplitude Cenozoic sea-level forcing systematically preconditioned passive-margin stratigraphy for UHS. Simulations of the Hunter offshore margin (NSW, Australia) reveal a fundamental contrast: greenhouse conditions promoted thicker (>25–50 m), laterally continuous, progradational packages with reservoir potential, whereas icehouse conditions generated vertically stacked, thinner (<25 m) units potentially suited for composite sealing systems, with the Eocene–Oligocene transition (∼34 Ma) separating these regimes. These findings suggest that sequential changes in sea-level forcing may have generated architectures favourable to reservoir and seal pairing and demonstrate that forward stratigraphic modelling provides a useful first-order screening approach where subsurface data are scarce.