Geology of the Waikato-King Country Region

The Waikato and King Country regions of New Zealand are built upon a basement of greywacke rocks, which form many of the hills. Much of the land to the west of the Waikato River and in the King Country to the south has been covered by limestone and sandstone, forming bluffs and a karst landscape. The volcanic cones of Karioi and Pirongia dominate the landscape near Raglan and Kawhia Harbours. To the east, the land has been covered with ignimbrite deposits from the Taupo Volcanic Zone. Large amounts of pumice from the Taupo Volcanic Zone have been deposited in the Waikato Basin and Hauraki Plains.

As with most of New Zealand, the basement rocks of the Waikato Region and King Country are composed of greywacke (indurated sandstone, siltstone and mudstone).

The Waipa Fault passes north–south through the Waikato-King Country region, from Taupiri, along the Waipa River, and south to near Ohura. It represents a major dividing line between different terranes.

Murihiku Terrane greywacke lies beneath the Waikato-King Country region on the western side, and outcrops to the west of the Waipa Fault, from south of Waikato Heads to Awakino. The Murihiku Terrane is considered to be an accretionary wedge of mainly volcanogenic forearc sediments. It was formed in Late Triassic to Late Jurassic times (220-145 Ma).

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