Abstract Details

ID: 1293
Title: Quantifying the response of Australian landscapes to climatic and tectonic forcing using cosmogenic isotope analysis

Cosmogenic 10Be concentrations in earth surface materials offer novel information on the rate and spatial patterns of bedrock erosion and basin-wide sediment generation which together influence continental denudation. This opens an opportunity to address the vexing question of how continental landscapes respond to climate and tectonic forcing. One hypothesis is that for equivalent long-term climatic variables, variations in tectonic activity will be reflected in bedrock and sediment 10Be concentrations such that more tectonically active landscapes will yield mean lower 10Be concentrations. We test this hypothesis across the Australian continent by sampling non-glaciated bedrock outcrops and stream sediments from 4 selected ‘end-member’ regions of contrasting climatic (large precipitation, temperature gradients) and tectonic (fault deformation, paleo-earthquake activity) variables with similar granitic lithologies. Localities included tropical northern Queensland and west coast Tasmania (>3000 mm/y), contrasting with late Quaternary neo-tectonically modified regions of the Flinders Ranges, South Australia (<200 mm/y), and tectonically passive but arid Port Hedland and the Darling Scarp, WA. Preliminary cosmogenic-derived erosion rates in regions proximal to active faults with surface ruptures in the last 100 kyr are 1-2 orders of magnitude higher than erosion rates in tectonically inactive regions, implying co-seismic rock fracturing and mass movement exert first order control on bedrock erosion rates on the 100 kyr timescale. Erosion rates derived from subhorizontal bedrock surfaces (and associated stream sediments) spanning Australia's most diverse climates with respect to annual precipitation and temperature gradients are typically <5 m/Ma, implying minimal climatic control on weathering of non-soil mantled bedrock. Cosmogenic nuclide data from across the continent provide quantitative evidence for strong tectonic and weak climatic influence on bedrock erosion.

Session: 64 Reconciling modern and Quaternary rates of landscape evolution
Authors: David Fink
Mark Quigley
Barry Kohn
Presenter:David Fink
Type: poster