Origin of the Torlesse Terrane and Coeval Rocks, North Island, New Zealand

Abstract

On the basis of differing areal extent, age, petrographic modes, and bulk chemical composition, the sandstones of the northern quarter of the Torlesse terrane are subdivided into four new petrofacies. A comparison of these petrofacies with existing South Island Torlesse classifications indicates continuation of the Triassic Rakaia subterrane and Late Jurassic–to–early Cretaceous Pahau subterrane into the central part of the North Island (as Axial-A and Axial-B petrofacies, respectively). The Waioeka petrofacies defines a new and provisional Late Jurassic-to–early Cretaceous Waioeka subterrane that is not present in the South Island. The Omaio petrofacies is common to deformed Albian basement sequences in the Torlesse of both islands, and in the Houhora Complex of Northland.

The composite Torlesse terrane evolved by Early Jurassic accretion of allochthonous Rakaia rocks followed by parautochthonous deposition of Pahau and Waioeka sandstones. Waioeka sandstones are compositionally similar to sandstones in the coeval eastern Waipapa terrane, but may have been dextrally displaced from their original depositional site by up to 300 km since the middle Cretaceous.