New Zealand Geologic Time Scale: Local Epochs and Stages
While the international geologic time scale provides a global framework for dating Earth's history, many nations utilize localized systems to better reflect their unique prehistoric records. New Zealand is a primary example, employing a specialized system of epochs (divisions of geologic time) and faunal stages (subdivisions based on fossil assemblages) to categorize its specific geological evolution.
Proposed by J. S. Crampton in 1995 and most recently calibrated in 2015, this system is widely used by New Zealand's earth scientists, geologists, and palaeontologists. While not formally adopted as the sole legal standard, it provides essential precision for studying the region's isolated prehistoric development.
Key Facts
- Local Nomenclature: Most New Zealand epochs and stages are named after local place names, predominantly of Māori origin.
- International Alignment: New Zealand uses the same primary periods as the international scale; only the subdivisions (epochs and stages) are renamed.
- Cenozoic Focus: Because much of New Zealand's geology is relatively recent, the local system is most detailed within the Cenozoic Era.
- Naming Convention: Stages are typically abbreviated as "Xx," where the first letter represents the epoch and the second lowercase letter represents the stage.
- Current Position: New Zealand is currently in the Haweran stage of the Wanganui epoch.
The Structure of the New Zealand Scale
The New Zealand system is designed to complement the International Geological Time Scale. While the broad periods remain the same, the local subdivisions allow researchers to pinpoint events using regional landmarks where rock dating is evident. It is important to note that New Zealand updates typically lag behind significant changes made to the international scale.
The Cenozoic Era
The Cenozoic is the most thoroughly documented era in the New Zealand scale. A notable example of the difference between local and international scales is the Wanganui epoch. Starting at 5.33 Ma (million years ago), the Wanganui epoch encompasses what the international scale divides into the Pliocene, Pleistocene, and Holocene epochs.
Currently, the region is in the Haweran stage, which began approximately 340,000 years ago and is named after the North Island town of Hāwera.
The Mesozoic and Palaeozoic Eras
In the Mesozoic Era, the scale covers the Cretaceous, Jurassic, and Triassic periods with localized epochs such as the Mata, Raukumara, and Oteke. As we move further back into the Palaeozoic Era, specifically prior to the Permian period, the local system becomes less distinct. Because very little New Zealand rock exists from the Devonian, Silurian, Ordovician, and Cambrian periods, these stages often align with Australian or international nomenclature.
Summary of Major New Zealand Geologic Divisions
| Era/Period | Epoch/Stage | Start Date (Ma) | International Equivalent / Note |
|---|---|---|---|
| Cenozoic | Wanganui Epoch | 5.33 | Pliocene, Pleistocene, Holocene |
| Cenozoic | Haweran Stage | 0.34 | Current stage |
| Mesozoic (Cretaceous) | Mata Epoch | 86.5 | Local subdivision |
| Mesozoic (Jurassic) | Herangi Epoch | 201.3 | Local subdivision |
| Palaeozoic (Permian) | D'Urville Epoch | 259.8 | Local subdivision |
| Palaeozoic (Cambrian) | Early Cambrian | 542.0 | Not subdivided locally |
Frequently Asked Questions
Why does New Zealand use its own geologic time scale?
New Zealand has an isolated prehistoric record. Using local place names for epochs and stages allows geologists to more accurately categorize and communicate the specific stratigraphic layers found within the country.
How does the New Zealand scale differ from the international one?
The primary periods (e.g., Jurassic, Cretaceous) are identical. The difference lies in the subdivisions; New Zealand uses local names for epochs and stages, and some of these local divisions span across multiple international epoch boundaries.
What does the abbreviation "Wq" stand for in the New Zealand scale?
Following the standard abbreviation format, "Wq" refers to the Haweran stage (q) within the Wanganui epoch (W).
Which geologic periods are least represented in New Zealand?
The Devonian, Silurian, Ordovician, and Cambrian periods have very little known rock record in New Zealand, which is why these periods often rely on international or Australian stage names.
Who proposed the current New Zealand geologic time scale?
The system was proposed by J. S. Crampton in 1995 and has since been used and calibrated by the scientific community, with a significant update occurring in 2015.