Craig Magee

Structures that facilitate fluid migration are common in sedimentary basins. We document several possible hydrothermal and/or volcanic vents located above a >157 km 2 , late Cretaceous volcanic field in the Great South Basin, offshore New Zealand. Three of the four vents are vertically stacked, suggesting episodic re‐use of the same fluid pathway between ca. 75 and 56 Ma. A palaeo‐pockmark dated to ca. 49 Ma and free gas occurring within strata ca. 21 Myr old are located directly above these stacked vents. The spatial association of the vents, pockmark and free gas further suggests re‐use of the fluid migration pathway(s) extended for over 54 Myr. Our results imply that reutilization of fluid flow pathways can affect the distribution of fluids within basins over prolonged periods, potentially impacting hydrocarbon/geothermal exploration and geohazard assessment.