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

Terrestrial cosmogenic nuclides (TCNs) such as Beryllium-10 (Be-10) are now routinely used to reconstruct erosional rates over tens of thousands of years at increasingly large basin scales (>100,000 km(2)). In Australia, however, the approach and its assumptions have not been systematically tested within a single, large drainage basin. This study measures Be-10 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 km(2). Beryllium-10 concentrations in sediment samples collected from the upstream headwater tributaries and mid-stream locations range from 1.8 to 2.89 x 10(5) atoms g(-1) and data confirm that nuclide concentrations are well and rapidly mixed downstream. Sediment from the same tributaries consistently yielded Be-10 concentrations in the range of their upstream samples. Overall, no decrease in Be-10 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 km(2)) is 18.47 m Ma(-1) which compares with the estimate at the end of the Burdekin catchment (130,000 km(2)) of 1622 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. Crown Copyright (C) 2015 Published by Elsevier B.V. All rights reserved.