Cretaceous and lower tertiary stratigraphy of the coastal strip between buttress point and ship creek, South Westland, New Zealand

Abstract

Abstract In South Westland upper Cretaceous and lower Tertiary rocks are found in a narrow coastal strip between Buttress Point and Ship Creek. The oldest unit, the Otumotu Formation (?M-R), is derived wholly from the Greenland Group, and consists of massive breccia-conglomerate in a maroon sandy matrix (lower member) overlain by grey sandstone, greywacke conglomerate, and carbonaceous shale (upper member). The overlying Tauperikaka Coal Measures (Mh) and shallow marine Whakapohai Sandstone (Mh) are both derived from a granitic source. In the southern part of the area, Whakapohai Sandstone is overlain by Arnott Basalt (Mh-Dt}, consisting of tuff, volcanic breccia, and flows of aphyric, mildly alkaline basalt; and Buttress Conglomerate (Mh-Dt), composed of boulders of andesite and dacite with minor Greenland Group, locally interbedded with a dacite flow. The younger Tokakoriri Formation (Dt-w) consists of calcareous mudstone and sandstone, and is conformably overlain by the Abbey Formation (Dw-Lwh), which is subdivided into three informal members: pure foraminiferal limestone (lower Abbey limestone), muddy foraminiferal limestone (middle Abbey limestone), and calcareous mudstone (upper Abbey mudstone). Basaltic volcanism was continuous from Paleocene to late Eocene time near the mouth of the Paringa River, and Otitia Basalt (?Dw-Ar) consists of tuff, volcanic breccia, and flows of alkali basalt (with minor hawaiite and trachyandesite) interbedded with the Abbey Formation.