Waikato Plains

[1] The plains are an area of once swampy land, much of which was drained by the early settlers, such as the Morrin brothers in the late 18th century[5] and is now intensively farmed.

[6] The basement is Waipapa Morrinsville Terrane greywacke formed in the Late Jurassic to Early Cretaceous (160-120 Ma).

The Hamilton Basin originally formed under water so marine Pliocene beds underlie Quaternary deposits that date from about 1.8 million years ago.

[2] The oldest deposits are called the Puketoka Formation which contains clays, sands, breccias and ignimbrite sheets from pyroclastic flow reaching the basin.

[2] The younger Waerenga Gravels are composed of weathered greywacke debris presumably deposited in fans extending from the surrounding ranges.

Location of the Waikato Plains
Waikato Plains from northeast towards Pirongia .
Orange shading shows the approximate area of the inactive Hamilton Basin intra-continental rift related to currently active intra-continental rifts North Island, New Zealand. These being the Hauraki Rift (purple), the modern Taupō Rift (red). The inactive old Taupō Rift (yellow) is also shown.