The gently-rolling Tablelands are a remnant of a once-extensive sea-level plain which over 45 million years ago stretched across New Zealand. As the land sank below sea-level, thick quartz gravels and then limestones were deposited on the ancient plain. In the last 14 million years the plain has been uplifted, mostly buckled and folded into mountains, its limestones and quartz gravels eroded off, but here and there remnants have survived, as with the Tablelands.