Geomorphological and sedimentary evidence for late Pleistocene to Holocene hydrological change along the Río Mamoré, Bolivian Amazon

Plotzki, Anna; May, J.-H.; Veit, Heinz; Preusser, F. (2013). Geomorphological and sedimentary evidence for late Pleistocene to Holocene hydrological change along the Río Mamoré, Bolivian Amazon. Journal of South American Earth Sciences, 47, pp. 230-242. Pergamon 10.1016/j.jsames.2013.08.003

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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 Río Mamoré (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 Río Mamoré 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-Mamoré – continued to be active at least until ∼5 ka, and likely even postdating 3 ka. An up to threefold increase in discharge is estimated for the modern Río Mamoré versus the paleo-Mamoré. The altered runoff regime may have triggered an avulsive shift towards the currently active Río Mamoré. 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 Río Grande system to the east of the Río Mamoré. Alternative explanations for the differences in dimensions of the paleo versus the modern Río Mamoré, i.e. contemporaneous activity of both rivers or alteration of site factors such as the channel/floodplain relationship, are considered to be unlikely.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Institute of Geography > Physical Geography > Unit Paleo-Geoecology
08 Faculty of Science > Institute of Geography

UniBE Contributor:

Plotzki, Anna and Veit, Heinz

Subjects:

900 History > 910 Geography & travel
500 Science > 550 Earth sciences & geology

ISSN:

0895-9811

Publisher:

Pergamon

Language:

English

Submitter:

Monika Wälti-Stampfli

Date Deposited:

17 Jan 2014 10:41

Last Modified:

19 Oct 2015 09:53

Publisher DOI:

10.1016/j.jsames.2013.08.003

Uncontrolled Keywords:

Llanos de Moxos, River avulsion, Paleohydrology, Meander cut-off

BORIS DOI:

10.7892/boris.39657

URI:

https://boris.unibe.ch/id/eprint/39657

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