New Zealand’s Geological Timescale
Our research has resulted in the establishment of the first fully integrated, comprehensive geological timescale for New Zealand, from Cambrian to Holocene.
The geological timescale is the time framework by which we date, correlate and classify rock formations and geological events. It provides the time framework for all studies of the history of the Earth and its life. It is used for assigning geological age to rocks, fossils and economic minerals, and for calibrating the rates of geological processes such as fault displacement and plate rotation, submergence, uplift and erosion of the land, earthquake frequency and volcanic activity. Rates of climate change, sea-level change, biodiversity change and organic evolution also are measured in terms of the geological timescale. Timescales play an important part in the search for petroleum and coal resources. It is essential therefore, that we have the most accurate and precise timescale available.
The New Zealand Geological Timescale is a regional geochronological timescale for the Permian to Pleistocene and comprises a sequence of stages defined in New Zealand outcrop sections. The local stages have served an important role in fine-scale geological mapping since the mid-20th Century, and continue to provide a standard for stratigraphic subdivision by integrating biostratigraphic data from various fossil groups with other stratigraphic criteria. This is fully described in GNS Science Monograph 22 "The New Zealand Geological Timescale" by Roger Cooper and co-contributors (2004).
Many of the most useful fossil groups for subsurface exploration in New Zealand Mesozoic-Cenozoic sedimentary basins have essentially local biogeographic distribution, or local ranges which differ from those of other regions because of differences in paleoclimate or ocean circulation, so the sequence of local stages which is closely tied to local fossils provides a more internally consistent, precise, and refined chronostratigraphy for routine use than international stages. Nevertheless, correlation with the International Geological Timescale is required for communication with the international community, and age-calibration of stage and substage boundaries for estimation of rates of geological processes and correlation with numerical age data from radiometric and other methods.
The status of the New Zealand stages is reviewed in a 2015 publication by Ian Raine and co-authors, SR2012-39 Geological Timescale report.pdf 2.92 MB. This revision, which is focussed on age-calibration of the stage boundaries, is based on calibration of the International Geological Timescale by Gradstein et al. (2012), and is consistent with the International Chronostratigraphic Chart 2014/10 (Cohen et al. 2014). A summary of the 2015 calibration is presented in a paper by Raine et al. (2015) in New Zealand journal of geology & geophysics.
The New Zealand Geological Timescale 2015 is also available as a ready-reference card from GNS Science Publications. A wall chart version of the card and a detailed summary table can be downloaded below.