The Processes that Shape the Continental Record

The continental crust is our only archive of Earth history; not just of the crust itself but of the hydrosphere, atmosphere and biosphere, and of the deep Earth through its interactions with the crust. This archive, like the rock record itself, is incomplete and much effort is focused on interrogating the crust to gain a clearer and more complete picture of Earth history. The continental rock record is episodic with, for example, ages of igneous crystallization, metamorphism, continental margins, and seawater and atmospheric proxies distributed about a series of peaks and troughs that in part correspond with the cycle of supercontinent assembly and dispersal. At the core of the debate is what these well-established peaks of ages in the geological record represent and how they develop. The peaks of ages correspond with periods of global assembly of continents to form supercontinents. The project will address whether the peaks of ages are primary features associated with supercontinent assembly or break up, or they are they secondary features representing greater preservation potential at the times of supercontinent assembly. Our work will focus on the Rodinian supercontinent cycle, which extends from initiation of convergent plate interaction around 1.7 Ga, to continental collision at 1.1-1.0 Ga during the Grenville orogeny, to final breakup of the supercontinent by 0.54 Ga.

Detrital zircons from sedimentary units throughout the supercontinent cycle provide a record of the magmatic activity for which the igneous rocks are often no longer preserved. We will determine (i) the ages ranges of magmatic activity preserved in the sedimentary rocks in the 600 Ma pre-collision phase, and (ii) how and when the distinctive Grenville peak of ages developed by comparing the zircon record from samples pre-, syn- and post- Rodinian supercontinent assembly with estimated volumes of magma and numbers of zircons produced during the same interval. This will differentiate primary generation processes from secondary processes, constraining when the dominant age peak developed, the tectonic processes that operated, and hence the method by which it developed.

The wider implications of when the continental crust formed are considerable. Studies of continental growth continue to uncritically assume that the geological and isotopic record provide insight into processes of crust formation. Until it can be established whether the record is the outcome of generational or preservational processes, or a combination of both, then drawing conclusions on this fundamental question in the Earth Sciences are premature. If the record is a preservational record then this impacts on understanding continental growth through time and on secondary questions of how the crustal record is used to unravel the temporal evolution of the hydrosphere and biosphere, and the distribution of mineral deposits.

This is blue skies research into a fundamental problem in the Earth Sciences, the formation of the continental crust. More widely an understanding of the time scales and processes involved in the evolution of the planet, and of life, should be integral parts of our education.

The proposed pathways to impact includes contributions to the GeoBus initiative based in St Andrews which is supported by NERC, through KE programme funding, and by industry. Its fundamental aim is to engage with school pupils to enhance their understanding of Earth Sciences and provide resources and support to teachers whose main subject may not be geology.

GeoBus is an educational outreach project developed by the Department of Earth Sciences at the University of St Andrews. The aim of GeoBus is to 1) support the teaching of Earth science in secondary schools by providing teaching resources that are not readily available to educators, 2) inspire young learners by introducing new Earth science research outcomes presented by researchers, and 3) provide a bridge between industry, HEIs, Research Councils, and schools in order to highlight career opportunities in geology specifically, and Earth sciences and STEM areas more broadly.

Earth science builds on all the pure sciences, and the newly funded NERC Programme Long-term Co-evolution of Life and the Planet will provide research outcomes that will be delivered to secondary schools to help convey concepts in chemistry, physics, biology, and geology. This includes new research knowledge on the origin and evolution of life, and how life can survive extreme conditions. We will develop two new web-based modules on Earth Time and Evolving Earth that will provide key information and learning materials on geological time and Earth's long-term geological history. We will work with the Outreach Coordinator for GeoBus to contribute to teaching packages, for example on the Geochronology of the Earth System and Isotopic and elemental proxies for tracking Earth System Evolution, and to an improved network for education in the Earth Sciences. Existing GeoBus teaching packages currently include Earth Resources, Key Minerals and Elements, Geothermal Energy, the Science of Climate Change, Snowball Earth, and Natural Hazards. The current coordinator is a geology graduate with a postgraduate diploma in science teaching, and who has about 2 years teaching experience in secondary schools. The GeoBus Advisory Board is made up of members who have decades of experience in education and education research. GeoBus therefore incorporates educational expertise and is an ideal forum for early career researchers, such as PDRAs and PGRAs, to develop cutting edge outreach and public engagement activities and experience. GeoBus will reach a broad audience and will be innovative and ambitious, introducing teaching packages and training support to a large number of science teachers across Scotland and England, providing equipment and materials which local authorities can not necessarily afford.

We request three months funding for a recent post-graduate student to help in developing teaching packages for GeoBus based on results of this project.