Geology of Mt Taitai, Tapuaeroa valley, Raukumara Peninsula

Abstract

Three lithological units are present at Mt Taitai. Siltstone with thin sandstone beds, locally sufficiently common to form thin-bedded units, enclosing lentils of sandstone, conglomerate, breccia and minor siltstone as lateral facies variants at different stratigraphic levels and here classed as Taitai Sandstone Member, are included in Mokoiwi Formation. Unconformably overlying Mokoiwi Formation and forming the central ridge of Mt Taitai, is Mangaohewa Formation which consists of a massive basal breccia, sandstone and siltstone. Siltstones of Mokoiwi Formation are complexly deformed, initially by soft rock deformation and subsequently by brittle deformation; some Taitai Sandstone units are isoclinally folded and open cross-folded, while others are fractured tabular sheets, and Mangaohewa Formation is folded into a syncline, the axial plane of which strikes west-north-west and dips steeply north.