Geology of the Kaikoura Area - GNS Science

This map and text illustrate the geology of the Kaikoura area, extending east from Murchison tosouthern Marlborough, and south to Waikari in north Canterbury. Onshore geology is mapped at ascale of 1:250 000 while offshore the bathymetry, thick Quaternary sedimentary deposits and majorstructural elements are shown. Geological information has been obtained from published andunpublished mapping and research by GNS Science geologists, from work by staff and students of theUniversity of Canterbury, Victoria University of Wellington and the University of Otago, fromoffshore mapping by the National Institute of Water and Atmosphere, and from mineral explorationreports. All data are held in a geographic information system and are available in digital format onrequest. The accompanying text summarises the geology and tectonic development, as well as thegeological hazards and the economic and engineering geology of the map area. The map is part of aseries initiated in 1996 which will cover the whole of New Zealand.The map area is mostly underlain by Mesozoic greywacke rocks of the Torlesse terrane, except in thenorthwest where narrow fault-bounded remnants of the Buller, Takaka, Brook Street, Murihiku, DunMountain-Maitai and Caples terranes occur, as well as the Median Batholith and other granitic rocks.Discontinuously preserved late Early Cretaceous to Pliocene, predominantly marine sedimentary andvolcanogenic rocks occur in the northwest, the east and the south of the map area. Quaternaryterrestrial sediments are widespread on land, including till, loess, scree, landslide, alluvial fan andalluvial terrace deposits. Numerous active faults of the Marlborough Fault System transect the maparea, marking the plate boundary zone between the Pacific and Australian tectonic plates. Several ofthese faults have moved in historic times contributing to the region's relatively high seismic hazard.The highest point of the Inland Kaikoura Range is Mt Tapuae-o-Uenuku (2885 m) where the summitregion is composed of erosion-resistant Cretaceous mafic igneous intrusive rocks and associatedhornfelsed Pahau terrane greywacke. The active Clarence Fault separates the Inland KaikouraRange from the distinctive Chalk Range in the middle distance, and the white screes there and inthe foreground emanate from Paleogene carbonate rocks.Photo: D.B. TownsendISBN 0-478-09925-8