NERC Isotope Geosciences Laboratory

Chronology > Stratigraphic record - Earth System Evolution

Stratigraphic record - Earth System Evolution

A major focus of the high-precision U-Th-Pb facility is working with the Earth Science community to provide robust temporal constraints to underpin Earth System evolution research. This is primarily focussed upon 'critical transitions' in Earth's history, and, more recently, on Mesozoic and Cenozoic climate change. Critical transitions in Earth's history often involve large-magnitude perturbations in global bio-geo-chemical cycles, such as those associated with the rise of atmospheric O₂ at ca. 2.5 Ga, or the rise of animals at ca. 600 Ma. As such, they illustrate the interplay between geodynamics, ocean and atmospheric chemistry, and biology.

Geochronology provides the only independent means of integrating the various disparate records of these events, thereby allowing us to assess relationships/feedbacks between the components of the Earth System.

NIGL plays a central role in international initiatives aimed at developing the next generation of geological time scales (EARTHTIME Initiative and its sister initiative in Europe). Our participation in the EARTHTIME project has been pivotal in that NIGL has, with international partners, been jointly responsible for the making, calibration and validation of a range of new isotope tracers and reference solutions that are being distributed to chronology laboratories all around the world to allow much better interlaboratory comparability of U-Pb dates for the next 20 years.

NIGL and the EARTHTIME Initiative

Over the past decade there has been considerable improvement in the level of precision attainable through radio-isotopic dating techniques with the result that currently precision is often greater than accuracy. Systematic sources of inaccuracy relate to both laboratory and decay-scheme specific calibrations. This is not something widely discussed outside the dating community but earth scientists are familiar with the constantly evolving timescale and debates surrounding the age of key boundaries. This situation imposes a major limitation on the calibration of geologic time and its exploitation for understanding Earth System processes.

The EARTHTIME Initiative was developed to tackle these issues with the dual aim of (1) achieving a high-resolution and stable calibration of geological time, and (2) increasing collaboration within and between the earth science sub-disciplines. This is a long term endeavour with major advances expected in the next decade.

The first phase of this initiative is aimed at tackling the technical issues of inter-calibration and the elimination of bias between chronometers. NIGL is one of the lead groups involved with this issue and is currently working with colleagues in the US and Europe on an effort to develop and calibrate the critical materials (isotopic tracers and standard solutions). These technical innovations will benefit the community in general and will be exploited at NIGL through the application of high-precision U-Th-Pb geochronology applied to the stratigraphic record.

NIGL is a participant in GTSnext, an EU Framework 7 Initial Training Network that has been approved for funding. The aim of this network is the training of the next generation of geoscientists with the skills required for the calibration of geologic time.

EARTHTIME article in Planet Earth magazine