Earth over Time Research at RSES
Introduction to Geochronology research
Our research varies from the determination of geological time through to the determination of processes active at specific periods in geologic time. The Earth is over 4.5 billion years old; hominid evolution has taken place over the past 3 million years; and our environment is changing over periods of years. We use a variety of methods for dating these events, everything in between, and even down to materials of historical derivation. Geological processes leave chemical and isotopic signatures. Much of our research lies in relating the signatures that we can now measure back to the processes that were involved. While many Earth processes are active today, there is always the possibility that conditions were different at different times. Observations of the geologic record provide insight into the processes that can range in size from the development of the planet as a whole, to the evolution and extinction of a single type of bacterium. Absolute age combined with this additional information provides a powerful tool to reconstruct rocks evolutions over time and describe important geological processesResearch topics
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Cosmogenic nuclides (He-3, Be-10, Ne-21, Al-26, Cl-36) have emerged as the most significant new tool for dating landscape features, and form the basis for a rapidly growing and exciting new field of geochronology. Cosmogenic nuclides can be used to date glacial and volcanic landscapes, as well as meteorite craters, fault displacements, landslides and to determine erosion rates. |
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To understand the tectonic evolution of the Earth we need to know when events occur, and how fast they take place. The 40 Ar/ 39 Ar system is unique in that it allows both geochronology and geospeedometry, as well as direct dating of fabrics, where the effect of different deformational events can be preserved in a single rock, or grain. Regional metamorphism as well as short-lived metamorphic events can be distinguished and dated using SHRIMP. Microstructural analysis with 40 Ar/ 39 Ar geochronology offers a powerful and complementary tool to determine the temporal evolution of mountain belts. |
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Australia is wonderfully rich in mineral resources (Fe, coal, gas, gold, etc) that are so vital to our economy, and at the same time worryingly scarce in other resources vital to our welfare (groundwater). The projects outlined below use field observations, experimental data and modelling to determine the physical and chemical processes ultimately controlling the formation and management of the resources available to our nation. |
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Planet Earth and the biosphere have evolved together for more than 3.5 billion years. Geobiology is the science that studies this co-evolution of life and environment in Earth's distant past and in present ecosystems. Local geobiological processes at present determine e.g. Whether estuaries and water reservoirs remain stable or whether they will drift into oxygen starvation. On a global scale, the interplay between life and the environment drives our planet's climate e.g. through generation and removal of greenhouse gases. |
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Radiocarbon is produced in the stratosphere by the collision of nitrogen atoms with thermal neutrons produced naturally by cosmic rays or artificially by atmospheric nuclear bomb testing. Atomic 14 C is rapidly oxidized to 14 CO 2 in the atmosphere and enters plants and animals via photosynthesis and the food chain. When an organism dies the 14 C decays back to Nitrogen 14. The half-life (the time it takes for half of the carbon-14 to decay) is 5730 years. After about 10 half-lives there is essentially no carbon-14 left in a sample. This results in a limit of this technique of 50-60,000 years, after which other radiometric techniques have to be used to age a sample. |
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A number of accessory minerals can be dated by the U-Th-Pb system to obtain a precise age. At RSES, precise U-Pb ages of crystal domains are measured either by SHRIMP ion microprobe or by Laser Ablation - ICPMS. Ages can then be correctly interpreted in geological terms if the environment and conditions of formation (pressure, temperature, fluids, deformation etc) of the dated mineral are known. |
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Paleogeographic reconstructions indicate that parts of the Australian continent have been exposed above sea level for hundreds of millions of years. A range of dating methods is being used to investigate the age of regolith and landforms in selected regions. Regolith is the weathered skin of the Earth's crust (everything from fresh air to fresh rock) and understanding its history is important for mineral exploration and land management. |