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New Zealand gets new geological map

New Zealand: GNS Science and Waikato University prepared and released a new geological map of the Hawke’s Bay and central North Island. The map is the final in a series of updated geological maps for New Zealand. The map and text describe the geology of an area that lies close to a tectonic plate boundary, stretching from the central North Island volcanic plateau and the lowlands of the Manawatu region, eastwards across the ranges into Hawke’s Bay.

The map updated previous geological maps that were published in the 1960s. It combines new information from fieldwork and hundreds of published and unpublished maps and scientific reports, including university thesis studies. The 7-year government funded project was a collaborative effort between GNS Science and Waikato University.

The large full-colour 1:250,000-scale map is tucked into a sleeve in the back cover of a 97-page companion book. The book includes stunning colour photographs of landscapes by Dougal Townsend, Kyle Bland and Lloyd Homer, illustrations of the great variety of volcanic and sedimentary rocks, and numerous diagrams summarising aspects of the geology.

The QMAP series of geological maps covers the whole of New Zealand. The project began in 1994 and, with the publication of QMAP Hawke’s Bay, the series of 21 maps is now completed. The new map has been generated from a computer database using GIS technology. This means that it can be updated when new information is obtained.

The oldest rocks in the map area form the Ruahine, Kaweka, and Ahimanawa ranges and the Kaimanawa Mountains. These rocks were deposited on the ocean floor between 200 and 145 million years ago – the Jurassic Period – and have since been uplifted.

Hills of limestone and sandstone now exposed in near Napier, Hastings, Waipukurau and the eastern margin of the Kaweka Range accumulated within a seaway that stretched from the Manawatu Gorge to Cape Kidnappers between one and three million years ago. Sandstone and limestone preserved along the Napier-Taihape Road are remnants of a seaway that once connected the Taihape area with Hawke’s Bay.

The map includes the eastern part of Tongariro National Park, situated at the southern end of the Taupo Volcanic Zone. The text describes the different types, ages and sources of the various lava, glacial and lahar deposits of Mts. Tongariro, Ngauruhoe and Ruapehu. Violent volcanic eruptions from calderas at Lake Taupo and farther north have sent pyroclastic flows into the area several times in the last 350 000 years.

The text describes a wide variety of natural hazards in the map area. These range from volcanic and earthquake hazards to landslides, coastal erosion and tsunami hazard.

Groundwater, aggregate and limestone are economically significant resources, and oil and gas are potential future resources.

The GNS Science team acknowledges input from numerous staff and students across all of New Zealand’s universities, as well as all landowners who granted access to their land. GNS Science also used offshore faults and folds obtained from the National Institute of Water and Atmospheric Research.

Digital data from the map are already being used extensively in a number of applied and scientific projects. End users expected to benefit include DoC, regional councils, engineers, mineral and petroleum exploration companies and earth scientists. People with an interest in the geology of this area should also find the map and text useful and informative.

Source: GNS Science