Geology Of The Wairarapa Area

Lee, J.M.; Begg, J.G. (comps) 2002
Geology of the Wairarapa area. Lower Hutt: Institute of Geological & Nuclear Sciences Limited.
Institute of Geological & Nuclear Sciences 1:250,000 geological map 11
66 p. + 1 fold. map

Abstract

The Wairarapa 1:250,000 geological map encompasses:

• c.7000 km² of land area in the southeastern part of the North Island, New Zealand.
• Nearly 11,000 km² of the adjacent offshore area.

Onshore Features:

• Tararua and Ruahine ranges: These axial ranges of the North Island separate the Horowhenua lowlands from the Pahiatua basin.
• Major valleys: Formed by the Manawatu, Mangatainoka, Mangahao, Ruamahanga, and Waingawa rivers, occupying a broad depression between the Tararua/Ruahine ranges and the eastern uplands.
• Eastern uplands: Undulating and dissected hill country situated between the Pahiatua and Masterton basins and the sea.
  • Puketoi and Waewaepa ranges in the north of the area reach the highest elevation.
• Uplifted marine terraces: Border much of the eastern coastline.

Offshore Features:

• Continental shelf: Gently sloping, extending 5-20 km to a depth of 150-200 m.
• Canyons and depressions: Incise the outer edge of the shelf.
• Continental slope: Beyond the shelf, it comprises a series of ridges and basins.
  • Northeast-trending highs and ridges: Indicate the location of anticlines underlain by west-dipping active thrust faults.

Plate Boundary and Geological Context:

• The deformation front of the Hikurangi Trough lies 65-125 km southeast of the Wairarapa coast, representing the boundary between the Pacific and Australian plates.
• The complex geology of the Wairarapa area is influenced by its proximity to the active plate boundary during the last c.25 million years.

(auth)