Warren, G.; Speden, I.G. 1978 The Piripauan and Haumurian stratotypes (Mata Series, Upper Cretaceous) and correlative sequences in the Haumuri Bluff district, south Marlborough (S56). Lower Hutt: New Zealand Geological Survey. New Zealand Geological Survey bulletin 92 60 p.
Abstract: The late Cretaceous rocks of Haumuri Bluff are for the most part rather poorly exposed on the south-east flank of an open anticline. Four formations are established. At the base 120 m of Okarahia Sandstone (yellow grey quartzose sandstone with a few lensoid ''Piripauan'' shellbeds near the base) unconformably overlies folded Torlesse rocks, and passes upwards into 15 m of yellowish Tarapuhi Grit, containing the lowest known appearance of the ''Haumurian'' fauna. Overlying are 240 m of massive dark grey Conway Siltstone with scattered large spherical calcareous concretions, a unit recognisable throughout much of the north-eastern coastal area of the South Island. This underlies 32 m of glauconitic and locally calcareous yellow or grey Claverley Sandstone, whose uppermost unit, the distinctive Teredo Limestone Member, conformably underlies the widespread early Tertiary Amuri Limestone. Rocks exposed in Mikonui Stream, a few kilometres to the north-west, include units - marine calcareous sandstone at the base, carbonaceous siltstone (non marine?) and bentonite - that are believed to be just older than the lowest part of the Okarahia Sandstone at Haumuri Bluff. The Conway Siltstone is interpreted as having accumulated slowly in a barred low-oxygen submarine depression with restricted circulation. The remaining units were deposited in near-shore, shallow-water, high-energy environments; deposition was entirely marine, except perhaps locally low in the Okarahia Sandstone. The Claverley Sandstone, and to a lesser extent the Okarahia Sandstone, show rapid lateral changes in lithology (especially carbonate content) and in thickness. Macrofossils, though locally abundant and diverse in the two lower formations, are mostly rare or absent; their biostratigraphic, and paleoecologic significance are discussed in detail. Calcareous microfossils, normally important constituents of the stratotypes of the latest Cretaceous and Cenozoic time-stratigraphic units in New Zealand, are virtually unknown. Four biostratigraphic units are recognised, all based wholly on macrofossils: (1) the Inoceramus pacificus - Dimitobelus lindsayi Assemblage-zone (Piripauan, but almost certainly beginning earlier than the ''type'' Piripauan); (2) the I. matotorus - Ostrea lapillicola Assemblage-zone (Haumurian); (3) the D. hectori Range-zone (Haumurian); and (4) a Clavagellid Bivalve [''Teredo''] Range-zone (Waipawan and possibly older). These units, though useful as a starting point for a comprehensive study of New Zealand late Cretaceous biostratigraphy, are all strongly facies-dependent, include few widely occurring species that have short stratigraphic ranges; and their use is plagued by doubts on the exact stratigraphic relationships and taxonomic identity of several species. Serious problems affect the definition of the Piripauan and Haumurian Stages - problems of original definition, exposure, fossil content, facies-dependence of the faunas, and disconti nuities in the succession. The type Piripauan Stages lies wholly within the Okarahia Sandstone, but a ''Piripauan'' fauna is present nearby in older rocks. No species diagnostic of either the ''Piripauan'' or ''Haumurian'' faunas have yet been discovered in the upper part of the Okarahia Sandstone. The type Haumurian Stages begins at the base of the Tarapuhi Grit and extends to an uncertain level within the Claverley Sandstone, whose highest unit, the Teredo Limestone Member, contains a Waipawan microfauna. No Teurian species have yet been recognised in the section. It is concluded that (a) that neither of the late Cretaceous time-stratigraphy is satisfactorily defined at present, and (b) that if formal redefinition of late Cretaceous time-stratigraphy is to be attempted, Haumuri Bluff is unsuitable as a type locality.
