Combining low temperature apatite thermochronology and cosmogenic isotope analysis in quantitative...
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Transcript of Combining low temperature apatite thermochronology and cosmogenic isotope analysis in quantitative...
Combining low temperature apatite thermochronology and
cosmogenic isotope analysis in quantitative landscape
evolution studies
Roderick Brown, Hermione Cockburn, Barry Kohn, David Belton, David Fink, Andrew Gleadow
and Michael Summerfield
The University of MelbourneAustralian Nuclear Science & Technology OrganisationThe University of Edinburgh
Conceptual landscapeevolution models
Numerical landscape evolution models
van der Beek et al. (2002)
Numerical landscape evolution models
Numerical landscape evolution models
Southern Africa
Drakensberg Escarpment
Landsat ETM+ 321RGB Image
Drakensberg Escarpment, Sani Pass
Sani Top Photograph by Alastair Fleming
Apatite Fission Track Age
Estimated Palaeogeothermal Gradients
Atlantic Margin, Namibia
Gamsberg Escarpment, ASTER VNIR Image
Gamsberg Plateau, ASTER VNIR Image
Gamsberg EscarpmentPhotograph by Hermione Cockburn
Gamsberg EscarpmentPhotograph by Hermione Cockburn
Gamsberg Plateau Transect
Gamsberg Escarpment Transect
South Eastern Australia
South Eastern Australia, 300m DEM
Brown Mountain Transect
50 km
Denudation since 110 Ma
Denudation since 65 Ma
Apatite U-Th/He Ages
Paired Apatite FT & He Ages
Apatite FT & U-Th/He Ages
Age of continental rifting
ANTARES Detector Array, ANSTO, Australia
Conclusions
Measured denudation rates and chronologies for the Gamsberg, Drakensberg and Brown Mountain escarpments are incompatible with a steady, parallel retreat model
Combined thermochronologic and cosmogenic datasets are capable of quantifying passive margin escarpment retreat rates
A viable alternative model involves the establishment of an escarpment at a major inland drainage divide with moderate to low subsequent retreat rates