Landscape responses to intraplate tectonism: Quantitative constraints from Be-10 nuclide abundances

摘要

Cosmogenic Be-10 concentrations in bedrock and alluvium combined with structural studies provide a novel approach for identifying neotectonic forcing of landscape evolution in mildly deforming continental interiors. Measured Be-10 concentrations in the Flinders Ranges indicate rapid and spatially variable rates of bedrock erosion in a catchment that has incurred at least three large, surface-rupturing earthquakes since similar to 67 ka. Be-10-derived erosion rates are lower where late Quaternary neotectonic activity is reduced or absent, implying that Be-10 concentration may act as a 'tracer' for disequilibrium landscapes responding to recent tectonism. Mechanisms for elevated erosion rates include (1) headward migration of fault-generated bedrock knickpoints and resultant oversteepening of stream profiles and catchment hillslopes and (2) liberation of bedrock material from catchment hillslopes via co-seismic shaking. Despite climatic influences on sediment production and transport, this study shows that tectonism can provide a dominant control on bedrock erosion rate and relief production in unglaciated mountain belts, even in intraplate settings where rates of crustal deformation are mild and earthquake activity is episodic. (C) 2007 Elsevier B.V.. All rights reserved.