The QMAP 1:250 000 Geological Map of New Zealand project

Abstract

In 1994 the QMAP 1:250 000 Geological Map of New Zealand project began with compilation of the Dunedin sheet. Nearly 18 years later, publication of the Hawke's Bay sheet marks the completion of all 21 maps. The adoption of geographic information systems (GIS) software for data capture, data management and map production has not only produced high cartographic quality maps, but also built the attribute-rich, nationally consistent QMAP GIS spatial database. The project cost about NZD $24M, and the results are now being used by government, industry and research organisations across infrastructure, geological hazard, resource and environmental areas. QMAP has added significantly to general knowledge of New Zealand's geological composition and history due to new discoveries and validation of concepts. Notable advances include work on the allochthons of Northland and East Coast; rationalisation of the Taupo Volcanic Zone and East Coast stratigraphic successions; differentiation of the Torlesse basement terranes; clarification of the transition from Otago Schist to Alpine Schist; determining the complex spatial and temporal history of igneous intrusions in Fiordland and Stewart Island; and mapping Quaternary sediments by oxygen isotope stage and depositional processes.

High-level stratigraphic scheme for New Zealand rocks

“…Many of New Zealand's medium-level lithostratigraphic volcanic, plutonic, sedimentary and metamorphic rock unit names have been in existence for many years and their adoption by GNS Science's Basin Studies and QMAP projects (King et al 1999;Rattenbury & Isaac 2012) reflects their ongoing usefulness. By using existing high-level stratigraphic names and introducing 14 new stratigraphic names, we have created a new, complete and holistic stratigraphic classification for onland and offshore New Zealand from the Kermadec to the Subantarctic islands.…”

“…But many of the formal and well-established groups of sedimentary rocks in New Zealand have not been erected on a strict lithostratigraphic basis in which constituent formations have significant and diagnostic lithologic properties in common. The QMAP project (Rattenbury & Isaac 2012) used a partly lithostratigraphic, partly tectonostratigraphic and partly chronostratigraphic approach, and this same pragmatic approach underpins Litho2014. We think no single methodology will yield a workable stratigraphic scheme for the whole range of plutonic, volcanic, sedimentary and metamorphic rocks present in New Zealand.…”

“…Outside these supergroups are c. 168 formally defined sedimentary and volcanic groups in current, common usage, and outside these groups are c. 208 formally defined sedimentary and volcanic formations in current, common usage. As a guide to current, common usage we have used King et al's (1999) synthesis of Cretaceous-Quaternary sedimentary successions in onshore and offshore basins and the recently completed QMAP geological map series, which is a synthesis of all onshore rock units (Rattenbury & Isaac 2012 With the exception of the new term 'superprovince', the basement scheme in Figs 1, 2 simply restates established, familiar and formal New Zealand usage of the root names province, terrane, pluton and suite. None of these commonly used terms are sanctioned by the International Stratigraphic Guide, which goes further in specifically recommending against using the terms pluton and batholith (Salvador 1994;Murphy & Salvador 1999).…”

The oroclinal bend in the South Island, New Zealand

“…As a result of recent 1:250,000 geological mapping (Rattenbury and Isaac, 2012), several deformed basement markers have been identified in the South Island that provide a more comprehensive picture of finite regional strain than does the Dun Mountain Ophiolite Belt alone. These include Buller-Takaka Terrane boundary, Darran Suite and Jurassic volcanic belt within the Median Batholith, Taieri-Wakatipu-Goulter Synform axial trace, the Haast Schist belt extrapolated to the Chatham Islands, Esk Head Melange, and bedding form surfaces within the Buller, Takaka and Torlesse terranes.…”

“…With the recent completion of new 1:250,000 scale mapping coverage for New Zealand (Rattenbury and Isaac, 2012), the Dun Mountain Ophiolite Belt and other basement markers can be accurately depicted at the scale of Fig. 2 (approximately 1:5,000,000).…”