Preprints
https://doi.org/10.5194/gchron-2021-23
https://doi.org/10.5194/gchron-2021-23

  27 Aug 2021

27 Aug 2021

Review status: this preprint is currently under review for the journal GChron.

Comparison of basin-scale in situ and meteoric 10Be erosion and denudation rates across a rainfall, slope, and elevation gradient at George River, northeast Tasmania, Australia

Leah VanLandingham1, Eric W. Portenga1, Edward C. Lefroy2, Paul R. Bierman3, and Alan J. Hidy4 Leah VanLandingham et al.
  • 1Geography and Geology Department, Eastern Michigan University, Ypsilanti, MI 48197, United States
  • 2Tasmanian Institute of Agriculture, University of Tasmania, Private Bag 98, Hobart 7001, Australia
  • 3Rubenstein School for Natural Resources and the Environment, University of Vermont, Burlington, VT 05405, United States
  • 4Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, Livermore, CA 94550, United States

Abstract. Long-term erosion rates in Tasmania, at the southern end of Australia’s Great Dividing Range, are poorly known, yet such knowledge is critical for making informed land-use decisions and improving ecological health of coastal ecosystems. Here, we present the first 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 (average 10.5 mm kyr−1). These new 10Bei-based erosion rates are strongly related to mean annual precipitation rates and elevation, and we suggest that the current East-West precipitation gradient across George River greatly influences erosion in northeast Tasmania. This stands in contrast to erosion rates along the mainland portions of Australia’s Great Dividing Range, which are more strongly related to basin slope. We also extract and measure meteoric 10Be (10Bem) from sediment grain coatings of the stream sand at each site, which we use to estimate 10Bem-based erosion and denudation rates for George River. 10Bem based erosion and denudation metrics, particularly those from the central and eastern tributaries, are also closely related to elevation and precipitation in the same manner as 10Bei erosion rates. Although 10Bem-based denudation rates replicate 10Bei erosion rates within a factor of two, 10Bem-based erosion rates are systematically 5–6x higher than 10Bei erosion rates. 10Bem erosion and denudation metrics for the westernmost headwater catchments are significantly lower than expected and have likely been affected by intensive and widespread topsoil erosion related to forestry, which delivers large volumes of sediment rich in 10Bem to tributary streams. The 10Bei erosion rates presented in this study may be useful for land managers seeking to restore ecological health of Tasmania’s estuaries by reducing sediment input to levels prior to landscape disturbance.

Leah VanLandingham et al.

Status: open (until 20 Oct 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on gchron-2021-23', Anonymous Referee #1, 12 Sep 2021 reply
  • RC2: 'Comment on gchron-2021-23', Anonymous Referee #2, 20 Sep 2021 reply

Leah VanLandingham et al.

Leah VanLandingham et al.

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Short summary
This study presents erosion rates of the George River and seven of its tributaries in northeast Tasmania, Australia. These erosion rates are the first measures of landscape change over millennial timescales for Tasmania. We demonstrate that erosion is closely linked to a topographic rainfall gradient across George River. Our findings may be useful for efforts to restore ecological health to Georges Bay by determining a pre-disturbance level of erosion and sediment delivery to this estuary.