Tectonic and Geologic History



The Geologic history of New Zealand can be broken up into 6 stages: 3 sedimentation periods and 3 mountain building periods.

1. The early sedimentation depositional phase, Cambrian to Devonian period (about 545 to 370 million years)
Earliest rock formations in new Zealand found today on South Island. At the time, New Zealand sat just off the ancient mega-continent of Gondwana. This included the formation of volcanic islands, which were eventually covered in sand and mud, subsequent land uplifting and erosion.

2. The Tuhua Orogeny, late Devonian to Carboniferous period (about 370 to 330 million years ago)
Pressure and uplift characterized this period – which formed mountains with new minerals under great heat and pressure. These mountains were eventually eroded and covered by younger materials.  For example, sandstone and mudstone became schist, known for parallel layering of minerals like mica. Plutonic intrusions formed granite and diorite.

3. The New Zealand Geosyncline, Carboniferous to Jurassic period (about 330 to 142 million years ago)
Massive sedimentation accumulation occured. These rocks and sediments form many of the mountain ranges we see in New Zealand to this day – and are the oldest rocks found on the North Island. Two major groups of rocks can be identified from this period: Torlesse supergroup and the Murihiku supergroup.

4. The Rangitata Orogeny, Early Cretaceous period (about 142 to 99 million years ago)
This is the first of three Mountain-forming periods: the sediments from the previous period were compressed and folded – with parts of the seafloor being caught in this process. You can see these today at Dun Mountain, West Dome and Red Hills on the South Island of New Zealand. Rocks in the West were folded simply, whereas Eastern rocks were severely deformed, with stacks of folds and complex faulting.
Dun Mountain. Retrieved from http://www.nelson.govt.nz/environment/nelson-nature/natural-environment/dun-mountain


5. The break-up, Cretacous to Oligocene period (99 to 24 million years ago)
Previously formed mountains undergo weathering and erosion. Roughly 85 million years ago, a rift valley formed, separating New Zealand region from Gondwana. By 35 million years ago, the majority of New Zealand was submerged. As the land began to sink, characteristic marine deposits were laid: calcareous and follilferous with limestone. New rift valleys were also forming between Australia and Antarctica.

6. The Kaikoura Orogeny, Miocene to Quaternary period (24 million years ago to modern)
Due to the spreading ridges between Australia and Antarctica, fault movements caused uplift, resulting in the Southern Alps. Principle mountain ranges of both the North and South Islands were uplifted and modern day New Zealand began taking shape. Subduction of the Pacific plate caused massive volcanism on the North Island and moving south over time, until reaching its present position along the Taupo Volcanic Zone.

 Map of New Zealand historical geological deposits. Retrieved from https://en.wikipedia.org/wiki/Geology_of_New_Zealand
Ulrich Lange, original (edited by Dushan Jugum 2018) - Edit of File:Map New Zealand Geology.jpg (Wikipedia Commons). I have added a key which matches the Geology of New Zealand Wikipedia article. The last key only had numbers.

Retrieved from course notes?????




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