Youngest sediments

Youngest Sediments Map

New Zealand's youngest sediments are unconsolidated rock materials, too soft or loosely bound to be considered as “rocks” and they are generally less than 2 million years in age. They are accumulations of gravel, sand and mud eroded from other materials and transported by water (rivers, glaciers, submarine currents) or gravity (screes and landslides) into valley floors, coastal plains, lakes and harbours.

Most flat low-lying ground around New Zealand is covered in sediment. The Canterbury Plains is a prime example resulting from extensive erosion of the Southern Alps and large rivers like the Rakaia and Waimakariri have carried huge amounts of gravel, sand and mud towards the eastern coast. These sediments have been deposited across the plain and exceed 200 m thickness in many places.

Similar sediments are also significant in other flat low-lying areas of the country including Southland, central Otago (Alexandra, Cromwell), West Coast, Kapiti to Manawatu, Hawke’s Bay, Gisborne, Bay of Plenty, Hamilton and south Auckland.

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