Stratigraphic nomenclature of the Omihi and Waikari Formations, North Canterbury

Abstract

Two new formation names are proposed—Omihi Formation (older) and Waikari Formation (younger). The Omihi Formation consists of five members: Berrydale Greensand, Gorries Creek Greensand, Tekoa Tuffs, Flaxdown limestone, and a redefined Weka Pass Stone. The Flaxdown limestone stratigraphically succeeds the Tekoa Tuffs in north-west North Canterbury. Elsewhere the members grade laterally into one another. Hence the names apply rather to the facies variants of the Omihi Formation. The Waikari Formation replaces the name Grey Marls, which is discarded. It consists of five members: Pahau Siltstone, Scargill Siltstone, Gowan Hill Sandstone, Glenesk Sandstone, and Tommys Creek Concretionary Sandstone. A lens of sandstone that in the mid-west and north of the region occurs at the same stratigraphic position within the Scargill Siltstone is named the Crantara Sandstone. These members occur in stratigraphic succession in some areas only. Elsewhere they grade laterally into one another, and hence the names apply rather to the facies variants of the Waikari Formation.