Comparison of basin-scale in situ and meteoric <sup>10</sup>Be erosion and denudation rates in felsic lithologies across an elevation gradient at the George River, northeast Tasmania, Australia

Abstract

Abstract. Long-term erosion rates in Tasmania, at the southern end of Australia's Great Dividing Range, are poorly known; yet, this knowledge is critical for making informed land-use decisions and improving the ecological health of coastal ecosystems. Here, we present quantitative, geologically relevant estimates of erosion rates for the George River basin, in northeast Tasmania, based on in situ-produced 10Be (10Bei) measured from stream sand at two trunk channel sites and seven tributaries (mean: 24.1±1.4 Mgkm-2yr-1; 1σ). These new 10Bei-based erosion rates are strongly related to elevation, which appears to control mean annual precipitation and temperature, suggesting that elevation-dependent surface processes influence rates of erosion in northeast Tasmania. Erosion rates are not correlated with slope in contrast to erosion rates along the mainland portions of Australia's Great Dividing Range. We also extracted and measured meteoric 10Be (10Bem) from grain coatings of sand-sized stream sediment at each site, which we normalize to measured concentrations of reactive 9Be and use to estimate 10Bem-based denudation rates for the George River. 10Bem/9Bereac denudation rates replicate 10Bei erosion rates within a factor of 3 but are highly sensitive to the value of 9Be that is found in bedrock (9Beparent), which was unmeasured in this study. 10Bem/9Bereac denudation rates seem sensitive to recent mining, forestry, and agricultural land use, all of which resulted in widespread topsoil disturbance. Our findings suggest that 10Bem/9Bereac denudation metrics will be most useful in drainage basins that are geologically homogeneous, where recent disturbances to topsoil profiles are minimal, and where 9Beparent is well constrained.

Physiography, foraging mobility, and the first peopling of Sahul

“…1c ) similar to those found in other post-orogenic landscapes and passive margin settings 87 and comparable to those published from cosmogenic radionuclides analysis for the region 87 , 88 (i.e., 10 Be-based basin-wide denudations rates). Similar rates are also predicted over the Tasmanian landscape 88 (max. ~58 mm/kyr); while the northern part of Sahul, along the Papua New Guinea orogen (Supplementary Fig.…”

Cosmogenic nuclide and solute flux data from central Cuban rivers emphasize the importance of both physical and chemical mass loss from tropical landscapes

“…The contrast between these two depictions of tropical denudation suggests that 10 Be-derived erosion rates for tropical areas may be incomplete representations of total mass loss from these landscapes because dissolved loads are only partially (and perhaps minimally) accounted for by measurements of 10 Be in river sand. This discrepancy highlights the need for more studies that compare rock dissolution rates and cosmogenicnuclide-derived rates to provide more accurate estimations of total landscape denudation (VanLandingham et al, 2022).…”