¹⁰Be-derived denudation rates from the Burdekin catchment: the largest contributor of sediment to the Great Barrier Reef

Abstract

Terrestrial cosmogenic nuclides (TCNs) such as Beryllium-10 (¹⁰Be) are now routinely used to reconstruct erosional rates over tens of thousands of years at increasingly large basin scales (> 100,000 km²). In Australia, however, the approach and its assumptions have not been systematically tested within a single, large drainage basin. This study measures ¹⁰Be concentrations in river sediments from the Burdekin catchment, one of Australia's largest coastal catchments, to determine long-term (> 10,000 years), time-integrated rates of sediment generation and denudation. A nested-sampling design was used to test for effects of increasing catchment scale on nuclide concentrations with upstream catchment areas ranging from 4 to 130,000 km². Beryllium-10 concentrations in sediment samples collected from the upstream headwater tributaries and mid-stream locations range from 1.8 to 2.89 × 10⁵ atoms g¯¹ and data confirm that nuclide concentrations are well and rapidly mixed downstream. Sediment from the same tributaries consistently yielded 10Be concentrations in the range of their upstream samples. Overall, no decrease in ¹⁰Be concentrations can be observed at the range of catchment scales measured here. The mean denudation rate for all river sediment samples throughout the Fanning subcatchment (1100 km²) is 18.47 m Ma¯¹, which compares with the estimate at the end of the Burdekin catchment (130,000 km²) of 16.22 m Ma¯¹. Nuclide concentrations in the lower gradient western and southern catchments show a higher degree of variability, and several complications emerged as a result of the contrasting geomorphic processes and settings. This study confirms the ability of TCNs to determine long-term denudation rates in Australia and highlights some important considerations in the model assumptions that may affect the accuracy of limited sampling in large, low-gradient catchments with long storage times.