Episodic sediment accumulation on Amazonian flood plains influenced by El Niño/Southern Oscillation

Aalto, R. E.; Maurice, Laurence; Dunne, Thomas; Montgomery, David R.; Nittrouer, Charles A.; Guyot, Jean‐Loup

doi:10.1038/nature02002

Cited by 283 publications

(285 citation statements)

References 23 publications

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“…River floodplain deposits, for example, have a large advection length scale ( Fig. 4; Supplementary Table 1) and have been shown to record metrics for flood discharge on annual to decadal timescales in the absence of morphodynamic filtering 45 . The connection between signal preservation and planar beds also lends support for the often-used assumption of a direct, linear connection between orbital forcing and bed-thickness patterns in horizontally laminated strata on Mars 48 .…”

Section: Discussionmentioning

confidence: 99%

“…Figure 4 shows examples in the advection regime where morphodynamics did not develop and where the sedimentary strata faithfully recorded allogenic forcing. In the advection regime (unlike the saturation regime), it is large systems that transport fine sediment that likely record environmental signals over the largest range in scales, potentially including preservations of signals that manifest over kilometres in length 45 (Fig. 4).…”

Section: Discussionmentioning

confidence: 99%

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Quantitative bounds on morphodynamics and implications for reading the sedimentary record

2014

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Sedimentary rocks are the archives of environmental conditions and ancient planetary surface processes that led to their formation. Reconstructions of Earth's past surface behaviour from the physical sedimentary record remain controversial, however, in part because we lack a quantitative framework to deconvolve internal dynamics of sediment-transport systems from environmental signal preservation. Internal dynamics of landscapes-a consequence of the coupling between bed topography, sediment transport and flow dynamics (morphodynamics)-result in regular and quasiperiodic landforms that abound on the Earth and other planets. Here, using theory and a data compilation of morphodynamic landforms that span a wide range of terrestrial, marine and planetary depositional systems, we show that the advection length for settling sediment sets bounds on the scales over which internal landscape dynamics operate. These bounds provide a universal palaeohydraulic reconstruction tool on planetary surfaces and allow for quantitative identification of depositional systems that may preserve tectonic, climatic and anthropogenic signals.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Quantitative bounds on morphodynamics and implications for reading the sedimentary record

2014

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“…In these large, accumulating floodplains of the Beni and Mamoré, present-day rates of sediment deposition are enormous (Guyot, 1993;Guyot et al, 1996;Aalto et al, 2003). From measuring suspended sediment concentrations in the Andean and floodplain Beni basin, Guyot (1993) and Guyot et al (1996) for example found that about half of the total sediment flux discharged from the Bolivian Andes is deposited in the adjacent Beni foreland basin.…”

Section: Study Areamentioning

confidence: 99%

From source to sink: Preserving the cosmogenic 10Be-derived denudation rate signal of the Bolivian Andes in sediment of the Beni and Mamoré foreland basins

Wittmann

Blanckenburg

Guyot³

et al. 2009

Earth and Planetary Science Letters

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The denudation rate signal of the Bolivian Andes as measured by cosmogenic 10 Be in sediment is preserved in the floodplain of adjacent foreland basins even though these basins store the sediment for thousands of years. This conclusion is drawn from comparing published Andean source area denudation rates with new cosmogenic 10 Be data as measured in the floodplains of the large Beni and Mamoré basins. For the entire Beni basin including the sediment producing Andes and the vast flooded plains of the foreland, the cosmogenic nuclide-derived denudation rate is 0.45 ± 0.06 mm/yr, while that of the Mamoré basin is 0.55 ± 0.19 mm/yr. By comparison, the respective Andean source areas erode at averaged rates of 0.37 ± 0.06 mm/yr (upper Beni), and at 0.56 ± 0.09 mm/yr (upper Mamoré). We notice a decrease in variability of denudation rate with increasing spatial scale as small-scale processes are averaged out. Sediment mixing within the floodplain damps scatter of nuclide-derived denudation rates picked up in the source area. On the temporal scale, a remarkable agreement between cosmogenic nuclide-derived rates averaging over a few kiloyears with those from fission track dating averaging over millions of years seems to suggest that cosmogenic nuclide-derived denudation rates capture the long-term erosional characteristics of the mountain belt. The sum of these observations suggests that any sample collected along a river traversing a floodplain will yield the denudation rate of the source area. This finding opens the unique possibility of constraining cosmogenic nuclide-derived paleo-sediment budgets for these large basins as the long-term, spatially-averaged denudation rate signal of the sediment-producing area is preserved in sedimentary archives.

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“…The Beni River is an upper Amazon tributary; its floodplain is a thoroughly investigated system where modern migration rates, recent sediment discharge, and bank erosion rates are well known (Guyot et al, 1996;Aalto, 2002;Aalto et al, 2003;Gautier et al, 2007). 10 Be concentrations of Beni River floodplain sediment have also been investigated in detail (Wittmann, 2008).…”

Section: The Beni River Examplementioning

confidence: 99%

Cosmogenic nuclide budgeting of floodplain sediment transfer

Wittmann

Blanckenburg

2009

Geomorphology

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Cosmogenic nuclides produced in quartz may either decay or accumulate while sediment is moved through a river basin. A change in nuclide concentration resulting from storage in a floodplain is potentially important in large drainage basins in which sediment is prone to repeated burial and remobilization as a river migrates through its floodplain. We have modeled depth-and time-dependent cosmogenic nuclide concentration changes for 10 Be, The cosmogenic nuclide composition of old deposits in currently inactive floodplains that have been isolated for periods of millions of years from the river that once deposited them are predicted to either increase or decrease in C, nuclide concentrations modeled for the in situ-produced variety of this nuclide are, however, sensitive to floodplain storage on residence times of < 20 ky. 10 Be and 26 Al concentration, depending on the depositional depth. These conditions can be evaluated using the 26 Al/ 10 We illustrate these models with examples from the Amazon basin. As predicted, modern bedload collected from an Amazon tributary, the Bolivian Beni River, shows no systematic change in nuclide concentration as sediment is moved through 500 km of floodplain by river meandering. In contrast, in the central Amazon floodplain currently untouched by the modern river system, low Be ratio that readily discloses the depth and duration of storage.26 Al/ 10 The important result of this analysis is that in all likely cases of active floodplains, cosmogenic Be ratios account for minimum burial depths of 5 to 10 m for a duration of > 5 My. 10 Be and 26 Al concentrations remain virtually unchanged over the interval sediment usually spends in the basin. Thus, spatially-averaged denudation rates of the sediment-producing area can be inferred throughout the entire basin, provided that nuclide production rates are scaled for the altitudes of the sediment-producing area only, because floodplain storage does not modify nuclide concentrations introduced from the sediment source area.

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Episodic sediment accumulation on Amazonian flood plains influenced by El Niño/Southern Oscillation

Cited by 283 publications

References 23 publications

Quantitative bounds on morphodynamics and implications for reading the sedimentary record

Quantitative bounds on morphodynamics and implications for reading the sedimentary record

From source to sink: Preserving the cosmogenic 10Be-derived denudation rate signal of the Bolivian Andes in sediment of the Beni and Mamoré foreland basins

Cosmogenic nuclide budgeting of floodplain sediment transfer

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