Continental shift

Impact: Paradigm shifts in our understanding of the formation of continents have contemporary implications for the study of climate records and the future of the resource sector

Wandering continents back to the dawn of time

Research led by UOW’s Associate Professor Allen Nutman pushes the first recognised extensive continent back to the very start of the geological record – with evidence of a single continent the research team named ‘Itsaqia’ that formed by 3600 million years ago.

This finding, published in 2015 in the American Journal of Science, is a stunning example of the geological principle ‘uniformitarianism’: natural processes that we see operating on Earth today resemble those operating in Earth’s Deep Time.

The evidence and concept of this earliest continent grew out of decades of research by A/Professor Nutman and colleagues at ANU and in the United Kingdom.

The history of all the oldest fragments of Earth’s crust had to be appraised and compared – meaning large amounts of time spent on field work in localities scattered around the globe, including Greenland, Canada and China, coupled with substantial laboratory studies ascertaining the absolute ages of Earth’s most ancient rocks by uranium-lead isotopic dating of zircons, extracted from these rocks.

Decades of work have pieced together evidence that the continent Itsaqia had formed by 3600 million years ago, but soon after started to split apart.

The research team are now setting their sights on what the discovery of Itsaqia has for climate records. Major climate events can be related to the formation and destruction of ancient supercontinents: Earth’s severest ice ages were triggered by global cooling.

This happens when the atmosphere-warming gas CO2 is reduced in concentration by chemical reaction with the large exposed land surfaces of supercontinents.

Therefore this question must be examined: Did Itsaqia trigger Earth’s first ice age?

Revealing the mechanisms of continental growth

Convergent margins are the engine room of planet Earth; rejuvenating Earth’s surface via continued uplift and erosion creating dynamic landscapes that are the cornerstone of diversity of life.

Understanding the geological past of convergent margins has implications for both the resources sector – they are responsible for the formation of most of the world’s mineral and energy resources – as well as understanding Earth’s climate.

Continental growth patterns at convergent margins are characterised by distinct ‘quantum collision’ events interspersed with more classical steady-state accretion, according to research by Dr Sol Buckman, who uses traditional geological mapping combined with sophisticated radiometric dating techniques from mountains in Australia and across the globe to study continental growth.

The information he is revealing is incompatible with current tectonic models, which have largely remained unchanged and unchallenged since the advent of the plate tectonic revolution in the 1970s.

Further research by Professor Allen Nutman has also revealed a completely new observation of particular mineral inclusions in zircons, which may be utilised in mineral exploration.

The ‘quantum tectonic’ model co-authored by Dr Buckman in 2012 also has important implications for the exploration of copper and gold deposits.

It is paradigm shifts like these, in geological thinking and new exploration methods that ‘see’ deeper into the Earth, which are crucial to the future of resource exploration and exploitation in years to come.