Eocene mounds are interpreted in the Central Ceduna Sub-basin.

They display geometries and internal configurations typical of biogenic build ups.

They show relationships with underlying reactivated faults intersecting the prospective Cretaceous petroleum systems.

A sub-bottom profile anomaly suggests a relationship between hydrocarbons seep and mound development.

We propose that natural hydrocarbon seep along faults can supply nutrients for localised biogenic mound growth.