Environmental Geoscience
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Dr John Webb: Research Interests
Karst paleoclimate, geomorphology and water geochemistry
Karst (usually limestone) terrains are characterised by underground drainage and cave systems, and often contain information absent from nonkarst areas.
Palaeoclimate records are preserved in the detailed isotopic and trace element variations within stalagmites:
- A joint project with archaeologist Prof Li Liu (Archaeology, La Trobe University) is studying stalagmites from caves in central China to reconstruct paleoclimates during the creation of the first city state in China . Quaternary palaeoclimates of southeastern Australia using cave deposits (speleothems and sediments).
- Palaeomagnetic studies of cave sediments at Buchan, eastern Victoria, and Wellington Caves, N.S.W., with Bob Musgrave (NSW Geological Survey), have shown that redeposited wind-blown sediments are reversed, dating a very early phase of aridity in southeastern Australia.
- Stable isotope studies of a stalagmite from a cave at Buchan by (with Albert Goede, University of Tasmania ) found a paleotemperature record that can be directly compared to that of the Northern Hemisphere.
Karst geomorphological studies have focussed on fitting the cave evolution of limestone areas in eastern and southern Australia into the regional landscape history:
- The Buchan karst in eastern Victoria preserves a record of landscape evolution extending back to the Eocene (with Brian Finlayson, University of Melbourne)
- Karst development in the Tertiary limestone aquifer of southeast S.A. and western Victoria was strongly influenced by both tectonic uplift along a major fault and Late Cainozoic sea level changes (PhD project by Sue White completed 2005).
- The spectacular tropical Chillagoe karst in north Queensland is an ancient landscape that appears to have developed mainly in the Mesozoic.
- The extensive Nullarbor Plain is one of the largest continuous karst areas in the world; the relatively limited cave development is due more to the flat landscape and porous limestone than the currently very arid climate (joint project with Julia James , University of Sydney ).
Hydrochemistry of waters in limestone terrains and relatinship to catchment landuse, cave formation and climate change:
- Hydrochemistry of limestone springs at Buchan in eastern Victoria is strongly relationed to catchment landuse (PhD project by Mark Ellaway, University of Melbourne )
- Lateral and temporal changes in the water geochemistry of cenotes (deep lakes that are collapsed caves) in the limestone aquifer in southeast South Australia (PhD project by Stan Lithco, completed 2003) have helped to understand how the stromatolites in the lakes are forming.
- Karst springs in western Victoria are more saline than most karst waters throughout the world, due to the input of water seeping through the saline soils developed on the basalts overlying the limestone (joint project with Ken Grimes, consultant
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