Abstract
Clusters of low circular domes and discs, each a few hundred metres high and a few kilometres across, have been mapped but not sampled during a Seabeam traverse of old (9–18 m.y.) oceanic crust at (at 19–20°S in the South Pacific, where they replace the typical lineated fault-block terrain for several hundred square kilometres. The landforms are probably produced by laccolith intrusion beneath a sediment cover in an off-axis volcanic province. Their overall shapes are distinctly different from the small volcanic shields that also dot the rise flank, and from small satellite cones that are abundant on archipelagic aprons, though some of the domes do bear small cratered shields and cones on their peripheries, and even shallow summit depressions.
