QM13 Kaikoura

The Kaikoura 1:250,000 geological map covers 18,100 km2 of Westland, Nelson, Marlborough and northern Canterbury in the South Island of New Zealand, and straddles the boundary between the Pacific and Australian tectonic plates.

The map area is cut by the Alpine, Awatere, Clarence, Hope and other major strike-slip faults, and includes a wide range of Paleozoic to Mesozoic rocks which form parts of eight tectonostratigraphic terranes. The early Paleozoic Buller and Takaka terranes, comprising sedimentary and volcano-sedimentary rocks respectively, are intruded by mid-Paleozoic granitic rocks of the Karamea Batholith and form the Western Province.

This province is separated from the Eastern Province by Mesozoic plutonic rocks of the Median Batholith. North of the Alpine Fault, the Eastern Province comprises the Permian-Jurassic, predominantly volcano-sedimentary Brook Street, Murihiku, Dun Mountain-Maitai and Caples terranes. South of the Alpine Fault the Eastern Province comprises the Triassic-Early Cretaceous sedimentary Rakaia and Pahau terranes, collectively termed the Torlesse composite terrane.

The Eastern Province and Western Province were juxtaposed in Late Jurassic to Early Cretaceous time, and subsequently formed a comparatively stable basement to younger Cretaceous and Cenozoic sedimentation. Localised fault activity and clastic sedimentary basin development in the late Early to Late Cretaceous, and again in Late Cenozoic time, contrast with the deposition of widespread, passive margin limestone and mudstone in the Paleocene, Eocene and Oligocene. Late Cenozoic clastic sedimentation reflects development of the present oblique-compressional plate boundary and uplift of the Southern Alps and other ranges. Quaternary glaciation deposited tills and glacial outwash gravels.

During warmer interglacical periods, high sea levels cut flights of marine terraces that have been subsequently uplifted. Mined mineral resources within the map area include alluvial gold, salt, coal, limestone, and rock aggregate. Recorded seeps and shows of oil and gas are sparse in the area; there has been no commercial hydrocarbon extraction, and the only petroleum exploration wells have been in the Murchison basin.

The Kaikoura map area is subject to severe natural hazards, including a high level of seismic activity from the Alpine, Awatere, Clarence, Hope and other active faults. These have potential for earthquake shaking, landsliding, liquefaction and ground rupture. Several large earthquakes with epicentres within or immediately adjacent to the map area have occurred within the last 160 years. Tsunami hazard may be from remote or local earthquakes or from submarine slumping, particularly within the Kaikoura Canyon immediately offshore. Storm-induced landsliding, rockfall and flooding are ongoing hazards.