Preprints
https://doi.org/10.5194/gchron-2021-31
https://doi.org/10.5194/gchron-2021-31

  02 Nov 2021

02 Nov 2021

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

Cosmogenic nuclide and solute flux data from central Cuba emphasize the importance of both physical and chemical denudation in highly weathered landscapes

Mae Kate Campbell1,2, Paul R. Bierman2,3, Amanda H. Schmidt4, Rita Sibello Hernández5, Alejandro García-Moya5, Lee B. Corbett1, Alan Hidy6, Héctor Cartas Águila5, Aniel Guillén Arruebarrena5, Greg Balco7, David Dethier8, and Marc Caffee9 Mae Kate Campbell et al.
  • 1Department of Geology, University of Vermont, Burlington, VT 05405, USA
  • 2Gund Institute for Environment, University of Vermont, Burlington, VT 05405
  • 3Rubenstein School of the Environment and Natural Resources, the University of Vermont, Burlington, VT 05405, USA
  • 4Department of Geology, Oberlin College, Oberlin, OH 44074, USA
  • 5Centro de Estudios Ambientales de Cienfuegos, Departamento de Estudio de la Contaminación Ambiental. AP 5, 59350, Ciudad Nuclear, Cienfuegos, Cuba
  • 6Atmospheric, Earth, and Energy Division, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA
  • 7Berkeley Geochronology Center, Berkeley, CA 94709, USA
  • 8Department of Geosciences, Williams College, Williamstown, MA 01267, USA
  • 9Department of Physics and Astronomy and Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, IN 47907, USA

Abstract. We consider measurements of both in situ produced cosmogenic nuclides and dissolved load flux to characterize the processes and pace of landscape change in central Cuba. The tropical landscape of Cuba is losing mass in multiple ways, making it difficult to quantify total denudation rates and thus to assess the impact of agricultural practices on rates of contemporary landscape change. Long-term sediment generation rates inferred from 26Al and 10Be concentrations in quartz extracted from central Cuban river sand range from 3.7–182 tons km−2 yr−1 (mean = 62, median = 57). Rock dissolution rates (24–154 tons km−2 yr−1; mean = 84, median = 78) inferred from stream solute loads exceed measured cosmogenic nuclide-derived sediment generation rates in 15 of 22 basins, indicating significant landscape-scale mass loss not reflected in the cosmogenic nuclide measurements. 26Al / 10Be ratios lower than that of surface production are consistent with the presence of a deep, mixed, regolith layer in the five basins that have the greatest disagreement between rock dissolution rates (high) and sediment generation rates inferred from cosmogenic nuclide concentrations (low). Our data show that accounting for the contribution of mineral dissolution at depth in calculations of total denudation is particularly important in the humid tropics, where dissolved load fluxes are high, and where mineral dissolution can occur many meters below the surface, beyond the penetration depth of most cosmic rays and thus the production of most cosmogenic nuclides. Relying on cosmogenic nuclide data or stream solute fluxes alone would both lead to underestimates of total landscape denudation in the central Cuba, emphasizing the importance of combining these approaches to fully capture mass loss in tropical landscapes.

Mae Kate Campbell et al.

Status: open (until 19 Dec 2021)

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Mae Kate Campbell et al.

Mae Kate Campbell et al.

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Short summary
We used cosmogenic radionuclides in detrital river sediment to measure physical erosion rates of watersheds in central Cuba; erosion rates are lower than chemical denudation rates in lowland watersheds. Data from two different cosmogenic nuclides suggest that some basins may have a deeper than typically modeled mixed layer and could have experienced significantly burial after or during exposure. We conclude that significant mass loss may occur at depth through chemical weathering processes.