Geology Of The Wellington Area

Begg, J.G.; Mazengarb, C. 1996
Geology of the Wellington area: sheets R27, R28, and part Q27, scale 1:50,000.
Lower Hutt: Institute of Geological & Nuclear Sciences.
Institute of Geological & Nuclear Sciences geological map 22
128 p. + 1 fold. map

Abstract:

Wellington is situated on a rugged, tectonically active landscape. The area is underlain by rocks of the Torlesse Complex, which are late Paleozoic to Mesozoic basement rocks forming the bedrock of large parts of New Zealand.

Key geological features of the Wellington area include:

• Two distinctive belts of Torlesse sediments:
  • Wellington belt
  • Rimutaka belt
    These correlate with Torlesse subterranes in the South Island.
• Principal rock types of the Torlesse Complex:
  • Greywacke (sandstone)
  • Argillite
  • Minor amounts of conglomerate
    These rocks were deposited in a deep marine environment and accreted during prolonged subduction along Gondwana's continental margin.
• Additional rock types within the Torlesse Complex:
  • Basalt
  • Chert
  • Coloured argillite
  • Limestones
    These likely represent seamounts and ocean floor material incorporated into the Torlesse sediments during subduction.

Deformational Features:

• Folds, faults, melange, and broken formation have developed as a result of subduction processes.
• The once horizontal bedrock layers now commonly stand close to vertical.

Metamorphic Grades:

• Wellington belt rocks: Metamorphosed to prehnite-pumpellyite grade, with some areas of low-grade schist.
• Rimutaka belt rocks: Exhibit a variety of metamorphic grades.

Seismic Activity:

The Wellington area is characterized by:

• Numerous active faults.
• The site of New Zealand's most powerful earthquake since European settlement.
• Frequent minor earthquakes.

Future severe earthquakes are likely to cause damage through:

• Ground shaking
• Fault rupture
• Liquefaction
• Landslides
• Tsunamis

(auth)