کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
6431453 | 1635162 | 2013 | 13 صفحه PDF | دانلود رایگان |

- Threefold increase in discharge of the RÃo Mamoré after 3Â ka.
- Increase in discharge may have caused avulsive river shift.
- Increase in discharge was possibly related to a shift in climatic conditions.
- Value of abandoned meanders in reconstructing paleohydrology is confirmed.
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 RÃo 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 RÃo 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 â¼5Â ka, and likely even postdating 3Â ka. An up to threefold increase in discharge is estimated for the modern RÃo Mamoré versus the paleo-Mamoré. The altered runoff regime may have triggered an avulsive shift towards the currently active RÃo 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 RÃo Grande system to the east of the RÃo Mamoré. Alternative explanations for the differences in dimensions of the paleo versus the modern RÃo Mamoré, i.e. contemporaneous activity of both rivers or alteration of site factors such as the channel/floodplain relationship, are considered to be unlikely.
Journal: Journal of South American Earth Sciences - Volume 47, November 2013, Pages 230-242