Bounty Trough

The Bounty Trough runs east-west, parallel with and immediately south of the Chatham Rise.

The Bounty Trough is a major submerged feature of the oceanography of the southwest Pacific Ocean, located off the east coast of New Zealand's South Island.

Extent

Located immediately to the south of the Chatham Rise, the Bounty Trough runs East-West for a distance of some 800 kilometres. The Bounty Trough's western extremity is less than 50 kilometres off the South Island's coast.

Much of The Bounty Trough lies at depths of 2000–3000 metres, and it marks an indentation in the "coastline" of the largely submerged continent of Zealandia.

Geology

A curious feature of the Bounty Trough is that it marks the continuation of several main river features in the South Island - a distinct series of channels exists in the base of the trough which is an extension of the Clutha and Waitaki River systems.

Both these rivers (especially the Clutha) are noted for their fast flow, but this alone would not account for the existence of the channels, though much of their current contours was probably shaped by sediment during the ice ages.

The channel system is the remnant of a Cretaceous rift formed via ocean-floor spreading at the time when Zealandia separated from Antarctica. The channels provide a major transportation system for sediments from the major rivers in the eastern South Island.