@article{fdi:010053058,
  title = {{S}ediment production and transport from in situ-produced cosmogenic {B}e-10 and river loads in the {N}apo {R}iver basin, an upper {A}mazon tributary of {E}cuador and {P}eru},
  author = {{W}ittmann, {H}. and von {B}lanckenburg, {F}. and {G}uyot, {J}ean-{L}oup and {L}araque, {A}lain and {B}ernal, {C}. and {K}ubik, {P}. {W}.},
  editor = {},
  language = {{ENG}},
  abstract = {{C}osmogenic nuclide-based denudation rates and published erosion rates from recent river gauging in the {N}apo {R}iver basin ({P}eruvian {A}mazonia) are used to decipher erosion and sedimentation processes along a 600 km long transect from the headwaters to the lowlands. {T}he sediment-producing headwaters to the {N}apo floodplain are the volcanically active {E}cuadorian {A}ndes, which discharge sediment at a cosmogenic nuclide-based denudation rate of 0.49 +/- 0.12 mm/yr. {T}his denudation rate was calculated from an average {B}e-10 nuclide concentration of 2.2 +/- 0.5 x 10(4) at/g(({Q}z)) that was measured in bedload-derived quartz. {W}ithin the {N}apo lowlands, a significant drop in trunk stream {B}e-10 nuclide concentrations relative to the {A}ndean hinterland is recorded, with an average concentration of 1.2 +/- 0.5 x 10(4) at/g(({Q}z)). {T}his nuclide concentration represents a mixture between the {B}e nuclide concentration of eroded floodplain deposits, and that of sediment eroded from the {A}ndean hinterland that is now carried in the trunk stream. {E}vidence for addition of sediment from the floodplain to the trunk stream is provided by published decadal-scale sediment flux measurements from gauging stations operated in the {N}apo basin, from which an increase from 12 x 10(6) t/yr at the outflow of the {A}ndes to 47 x 10(6) t/yr at the confluence with the {S}olimoes (upper {A}mazon {R}iver) is recorded. {T}herefore, approximately 35 x 10(6) t of floodplain sediment are added annually to the active {N}apo trunk stream. {C}ombined with our nuclide concentration measurements, we can estimate that the eroded floodplain deposits yield a nuclide concentration of similar to 0.9 x 10(4) at/g({Q}) only. {U}nder steady state surface erosion conditions, this nuclide concentration would translate to a denudation rate of the floodplain of similar to 0.47 mm/yr. {H}owever, we have no geomorphologic explanation for this high denudation rate within the low relief floodplain and thus suggest that this low-nuclide concentrated sediment is {A}ndean-derived and would have been deposited in the floodplain at a time when erosion rates of the {A}ndes were elevated. {T}herefore, the recently eroded floodplain sediment provides an {A}ndean "paleo denudation rate" of 1.2 mm/yr that was calculated for high {A}ndean production rates. {A} likely period for elevated erosion rates is the {LGM}, where climate and vegetation cover of the {A}ndes differed from that of the {H}olocene. {A} possible cause for the erosion of the floodplain is the tectonic uplift of the {E}astern {A}ndes, which progressively shifts the {N}apo {R}iver northwards. {H}ence, the river cuts into ancient lowland sediment, which is admixed to the {A}ndean sediment carried in the main {N}apo {R}iver.},
  keywords = {{E}rosion ; {D}enudation ; {C}osmogenic beryllium-10 ; {I}n situ-produced {B}e-10 ; {R}iver loads ; {A}ndes ; {S}ediment transport ; {N}apo basin ; {O}riente basin ; {C}hannel-floodplain exchange},
  booktitle = {},
  journal = {{J}ournal of {S}outh {A}merican {E}arth {S}ciences},
  volume = {31},
  numero = {1},
  pages = {45--53},
  ISSN = {0895-9811},
  year = {2011},
  DOI = {10.1016/j.jsames.2010.09.004},
  URL = {https://www.documentation.ird.fr/hor/fdi:010053058},
}