Research ArticleGEOLOGY

Million-year lag times in a post-orogenic sediment conveyor

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Science Advances  19 Jun 2020:
Vol. 6, no. 25, eaaz8845
DOI: 10.1126/sciadv.aaz8845
  • Fig. 1 Compilation of luminescence ages, a regolith depth map of the MDB, and location of sample sites.

    (A and B) Optically stimulated luminescence (OSL) and thermoluminescence (TL) ages in MDB and the LEB fluvial deposits taken from the OCTOPUS database (22) and maps showing their spatial distribution. (C) Map of the MDB showing the distribution of regolith depth (24) and the location of sample sites for cosmogenic radionuclide analyses. Blue circles are headwater samples, red circles are upland samples, and black circles are lowland samples. The red dashed line shows the approximate boundary between the Murray (south) and Darling (north) sub-basins. On the regolith depth map, the colors yellow, orange, and red demarcate the approximate extent of the alluvial plains (24, 25).

  • Fig. 2 Cosmogenic 26Al/10Be burial plots.

    (A) Murray Basin samples (including the Snowy River). (B) Darling Basin samples. Samples that have experienced continuous exposure to cosmic radiation will plot within the orange envelope. Samples that have experienced a complex exposure history involving one or more episodes of burial and cessation of nuclide production (i.e., samples undergoing storage) will plot in the yellow shaded area. The distance between the simple exposure/erosion history envelope and a data point is proportional to the duration of burial, with samples buried for longer plotting further away from the orange envelope. Orange curves show 1- and 2-Ma burial isochrons. Uncertainties (ellipses) are shown at the 2σ level. Colors indicate sample provenance, as shown in Fig. 1.

  • Fig. 3 Cosmogenic 26Al/10Be/14C burial plots.

    (A and B) Murray Basin samples. (C and D) Darling Basin samples. (A) and (C) are the same as Fig. 2 but only show those samples where 26Al, 10Be, and 14C were analyzed to allow for easy comparison between 26Al/10Be and 10Be/14C ratios. Samples that have experienced a complex exposure history (i.e., samples undergoing storage) will plot in the yellow shaded area. Uncertainties are shown at 2σ level, and orange curves show burial isochrons. Colors indicate sample provenance, as shown in Fig. 1.

  • Fig. 4 Drainage network and distribution of apparent burial ages.

    Orange and red shaded boxes show 26Al/10Be age ranges, and black and gray shaded boxes show 14C/10Be age ranges. Ages are expressed in thousand years, and age ranges represent 95% confidence intervals. Red circles are upland samples, and black circles are lowland samples.

  • Fig. 5 10Be-based denudation rates and 26Al/10Be ratios recorded in rivers draining Australia and other Gondwana segments.

    (A) Comparison of published 10Be-based denudation rates (22) with those recorded in the MDB (this study): 1, Africa; 2, the Western Ghat Mountains of India; 3, the Brazilian Atlantic continental margin and the Guyana and Brazilian shields; 4, MDB. Horizontal lines show the global median and mean denudation rates calculated using the OCTOPUS database (22). Horizontal band indicates the range of MDB denudation rates. (B and C) Cosmogenic 26Al/10Be burial plots showing published 26Al and 10Be data for (B) large rivers draining the African continent and central Australia (33) and (C) rivers draining the Guyana and Brazilian shields (17). Note how virtually all samples in (B) and (C) plot in the yellow shaded area indicating a complex exposure history. Uncertainties are shown at 2σ level, and orange curves show burial isochrons.

Supplementary Materials

  • Supplementary Materials

    Million-year lag times in a post-orogenic sediment conveyor

    R.-H. Fülöp, A. T. Codilean, K. M. Wilcken, T. J. Cohen, D. Fink, A. M. Smith, B. Yang, V. A. Levchenko, L. Wacker, S. K. Marx, N. Stromsoe, T. Fujioka, T. J. Dunai

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