The geology of the Mount Adams area, Southern Wairarapa

Abstract

The stratigraphy and structure of the Mount Adams area, Eastern Wairarapa is described and illustrated by a map. Mokoiwian mudstone and sandstone is faulted against Upper Cretaceous to Lower Tertiary sediments to the east, and unconformably overlain by Upper Miocene sediments to the north. Massive sandstone with some siltstone and conglomerate, possibly Korangan in age, conformably overlies the Mokoiwian mudstone and is unconformably overlain by Upper Miocene sediments to the west. Upper Cretaceous and Lower Tertiary strata in upward succession are: Glenburn Formation graded bedded sandstone and siltstone, massive siltstone, grit and conglomerate, Ngaterian to Arowhanan in age; Longbush Formation graded bedded micaceous sandstone and siltstone, Mangaotanean to Teratan in age; Tutu Formation massive sandstone and graded bedded glauconitic sandstone and siltstone, Piripauan in age; Whangai Formation consisting of siliceous siltstone, sandy siltstone, greensand and flint, Haumurian to Teurian in age; Kaiwhata Limestone consisting of hard flinty limestone, greensand, calcareous sandstone and siltstone, and hard calcareous argillite, Teurian in age; and Huatokitoki Formation consisting of bentonitic siltstone, glauconitic siltstone, chocolate siltstone and slump breccia, Waipawan to Porangan in age. Upper Miocene sediments, Hurupi Formation, consist of fossiliferous massive siltstone and some thin graded sandstone layers. Several dolerite and teschenite sills, which intrude Teratan and Teurian strata, are similar in composition and considered to be comagmatic with intrusions further north. Variolitic basalts are interstratified with Mokoiwian and Haumurian strata. Cretaceo-Tertiary rocks are severely faulted. They have been deformed by both diastrophic movement and slumping and both types of deformation are aligned along north-north-east trending axes. Upper Miocene sediments in the eastern side of the Hinakura Valley are displaced by north-west trending faults.