Geomorphology Research at RSES
Introduction to Geomorphology research
Production and transport of soils and sediments, and cosmogenic nuclides
This research addresses three basic questions concerning soil and regolith: (i) what are the natural, sustainable rates of soil production and erosion? (ii) what are the rates of sediment transport from hill-slopes to rivers? (iii) what is the residence time of sediment in river and floodplain systems?
The research is significant for the usage and conservation of soil, sediments
and weathered deposits, and also has implications for mineral exploration
and long-term movement of sedimentary wastes. The impacts of past climatic
changes on soils and regolith also are a subject of study.
Cosmogenic nuclides, produced in surface rocks and sediments by cosmic ray reactions, are powerful tools for determining the rates of production, transport and erosion of mineral soil and weathered detritus (i.e. regolith). Although slow, these rates can be determined from the concentrations of cosmogenic nuclides, which depend on the history of erosion, exposure and burial of near-surface materials, although problems arise where erosion rates have varied as a result of climatic changes and/or tectonic movements. To overcome ambiguities we utilise combined measurements of cosmogenic radioactive 10 Be and 26 Al and stable 21 Ne, utilising a unique array of accelerator mass spectrometry and noble gas mass spectrometry.
Research topics
 |
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. |
|
 |
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. |
|
 |
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 are being used to investigate the age of regolith in selected regions. |