Orbital Cycles Aid Shale Oil Prediction in Sichuan Basin

Subtle shifts in Earth's orbit may hold the key to predicting ancient oil-rich shale deposits hidden beneath China's Sichuan Basin.

A new study published in the Journal of Paleogeography (Chinese edition) on September 30, 2025, demonstrates how sediment cores and gamma-ray data reveal correlations between orbital cycles and shale oil formation patterns.

Researchers analyzed 4 cm of sediment accumulation per 1,000 years in the basin, aligning rock layers with Milankovitch cycles—periodic changes in Earth's orbital eccentricity, axial tilt, and precession.

During high eccentricity periods, the study found evidence of warmer, wetter lake conditions that promoted organic-rich mudstone deposition.

Conversely, low eccentricity phases correlated with drier conditions and sand-rich sediment flows that altered lake environments.

The methodology relies on precise sediment layer dating to match geological records with astronomical cycles. By contrast, the team notes that while this framework improves predictive models for shale oil locations, it does not identify new reserves.

The study's authors emphasize that their findings provide a chronological tool for locating existing deposits rather than assessing their economic viability.