The Osbourn Trough, is a 900 km (560 mi)-long[1] extinct mid-ocean ridge, that may have stopped spreading as recently as 79 million years ago.
The Osbourn Trough is key to understanding the postulated breakup mechanism of the historic massive Ontong Java-Manihiki-Hikurangi large igneous province (LIP),[1] as it has been shown to be the spreading centre that lead to the separation of the Manihiki Plateau to its north and the Hikurangi Plateau to its south close to New Zealand.
[7] Further the Osbourn Trough is a more prominent feature in gravity anomaly studies than in bathymetric data.
[7] The Glomar Challenger had surveyed part of the area by 1987 but the global magnetism data was not available to allow an understanding that a large undersea feature existed.
[7] The precise timing of the Osborne Trough formation has been a matter of some debate as it is important to dating geological events in the South Pacific region, in particular subduction cessation.