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Geomorphological and sedimentary evidence for late Pleistocene to Holocene hydrological change along the Rio Mamore, Bolivian Amazon
Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
2013 (English)In: Journal of South American Earth Sciences, ISSN 0895-9811, Vol. 47, 230-242 p.Article in journal (Refereed) Published
Abstract [en]

Aerial photography and satellite imagery reveal manifold geomorphological evidence of a dynamic evolution of past and present rivers in the Bolivian Amazon. Comparison of oxbow lake and meander scar dimensions along an inactive meander belt of the Rio Mamore (Llanos de Moxos, north-eastern Bolivia) and its modern counterpart suggests significant regional paleohydrological variability. We used these features as geomorphological and sedimentary archives to enhance our understanding of longer-term variations of the fluvial system. Late Pleistocene to Holocene hydrological changes of the Rio Mamore are inferred from: (i) the analysis of satellite imagery, (ii) discharge estimates from meander morphology, (iii) stratigraphic, and (iv) chronological information based on luminescence and radiocarbon dating. The combined data from three oxbows indicate that the now abandoned meander belt - the paleo-Mamore - continued to be active at least until similar to 5 ka, and likely even postdating 3 ka. An up to threefold increase in discharge is estimated for the modern Rio Mamore versus the paleo-Mamore. The altered runoff regime may have triggered an avulsive shift towards the currently active Rio Mamore. The preceding increase in discharge in turn, was possibly related to a shift in climatic conditions, which changed markedly between the mid- and late Holocene in tropical South America. In addition, it may have been the indirect result of capturing the avulsive Rio Grande system to the east of the Rio Mamore. Alternative explanations for the differences in dimensions of the paleo versus the modern Rio Mamore, i.e. contemporaneous activity of both rivers or alteration of site factors such as the channel/floodplain relationship, are considered to be unlikely.

Place, publisher, year, edition, pages
2013. Vol. 47, 230-242 p.
Keyword [en]
Llanos de Moxos, River avulsion, Paleohydrology, Meander cut-off
National Category
Geosciences, Multidisciplinary
URN: urn:nbn:se:su:diva-96872DOI: 10.1016/j.jsames.2013.08.003ISI: 000326212600018OAI: diva2:668266


Funding agency:

Swiss National Science Foundation SNF 200021-1222

Available from: 2013-11-29 Created: 2013-11-28 Last updated: 2013-12-04Bibliographically approved

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Preusser, Frank
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