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

Plotzki, Anna; May, Jan-Hendrik; Preusser, Frank; Veit, Heinz

doi:10.1016/j.jsames.2013.08.003

Cited by 18 publications

(21 citation statements)

References 66 publications

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“…More recently, however, it has been suggested that the megafan of Grande River did not follow a counter clockwise movement (Plotzki, 2013). The study of an interior delta/sedimentary lobe at the distal part of one of the Grande River palaeocourses, seems to indicate that the Grande River avulsive phase may have been triggered by an increase in river discharge or sedimentary load that could have been brought about by a mid-to late Holocene climate shift towards wetter conditions (Lombardo et al, 2012;Plotzki et al, 2013). Similarly, the avulsion of the Mamoré seems to be related to an increase in discharge probably caused by a change in climate .…”

Section: Rivers and Palaeoriversmentioning

confidence: 94%

“…During the mid-to late Holocene, a large transformation occurred in the central and southern LM. Perhaps due to a climate shift towards wetter conditions (Lombardo et al, 2012;Plotzki et al, 2013), coupled with basinal subsidence (Hanagarth, 1993;Dumont and Fournier, 1994), the Mamoré established its modern position and the Grande River formed a large distributary system (Fig. 12d).…”

Section: Late Holocenementioning

confidence: 99%

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Neotectonics, flooding patterns and landscape evolution in southern Amazonia

Lombardo

2014

Earth Surf. Dynam.

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Abstract. The paper examines the role of neotectonic activity in the evolution of the landscape in southern Amazonia during the Holocene. It uses both new and published data based on the analysis of remote sensing imagery and extensive field work in the Llanos de Moxos, Bolivian Amazon. The study of the region's modern and palaeorivers, ria lakes, palaeosols and topography provides a strong case in favour of the thesis that the northern part of the Llanos de Moxos constitutes the southern margin of the Fitzcarrald Arch and that it has experienced uplift during the Holocene. The paper assesses the extent and timing of the neotectonic activity in light of the new data and reconstructs the evolution of the landscape since the late Pleistocene. The evidence suggests that at least two uplift events took place: a first uplift in the late Pleistocene, which caused the formation of Lake Oceano, and a second uplift during the mid-Holocene, which formed Lake Rogaguado. These two uplifts appear to be linked to the knickpoints observed close to the towns of Guayaramerín and Puerto Siles respectively. The backwater effect due to these uplifts transformed the region's major rivers in seasonal ria lakes, causing the deposition of thick organic clay layers along the Beni, Mamoré and Madre de Dios river banks. I argue that neotectonic episodes could have dramatically changed the drainage of the Llanos de Moxos, determining its flooding regime, soil properties and forest-savannah ecotone. These results stress the need for geomorphologists, palaeo-ecologists and archaeologists to take into account neotectonics when reconstructing the region's past.

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Section: Rivers and Palaeoriversmentioning

confidence: 94%

Section: Late Holocenementioning

confidence: 99%

Neotectonics, flooding patterns and landscape evolution in southern Amazonia

Lombardo

2014

Earth Surf. Dynam.

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“…Even less information from marginal regions such as south-western Amazonia and the Llanos de Moxos (LM) lowlands of Bolivia is known, although several studies have reported large-scale river migrations of the Beni, Mamoré and Grande Rivers (Allenby, 1988;Dumont, 1996;Hanagarth and Sarmiento, 1990;Hanagarth, 1993;Lombardo et al, 2012;Plafker, 1964;Plotzki et al, 2011). Avulsive shifts along the Mamoré and Grande Rivers must have occurred in the mid to late Holocene (Lombardo et al, 2012;Plotzki et al, 2013), but no comprehensive geomorphological or chronological dataset is available for the older, Pleistocene fluvial system in the region. In the southern Llanos de Moxos, remnants of the fluvial lobe of the Grande River as well as other traces of former 3 rivers were grouped in two generations of paleochannels (Lombardo et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

Geomorphology and evolution of the late Pleistocene to Holocene fluvial system in the south-eastern Llanos de Moxos, Bolivian Amazon

Plotzki¹,

May²,

Preusser³

et al. 2015

CATENA

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In the Bolivian Amazon several paleochannel generations are preserved. Their wide spectrum of morphologies clearly provides crucial information on the type and magnitude of geomorphic and hydrological changes within the drainage network of the Andean foreland. Therefore, in this study we mapped geomorphological characteristics of paleochannels, and applied radiocarbon and optically stimulated luminescence dating. Seven paleochannel generations are identified. Significant changes in sinuosity, channel widths and river pattern are observed for the successive paleochannel generations. Our results clearly reflect at least three different geomorphic and hydrological periods in the evolution of the fluvial system since the late Pleistocene. Changes in discharge and sediment load may be controlled by combinations of two interrelated mechanisms: (i) spatial changes and re-organizations of the drainage network in the upper catchment, and/or (ii) climate changes with their associated local to catchment-scale modifications in vegetation cover, and changes in discharge, inundation frequencies and magnitudes, which have likely affected the evolution of the fluvial system in the Llanos de Moxos. In summary, our study has revealed the enormous potential which geomorphic mapping and analysis combined with luminescence based chronologies hold for the reconstruction of the late Pleistocene to recent fluvial system in a large portion of Amazonia. AbstractIn the Bolivian Amazon several paleochannel generations are preserved. Their wide spectrum of morphologies clearly provides crucial information on the type and magnitude of geomorphic and hydrological changes within the drainage network of the Andean foreland.Therefore, in this study we mapped geomorphological characteristics of paleochannels, and applied radiocarbon and optically stimulated luminescence dating. Seven paleochannel generations are identified. Significant changes in sinuosity, channel widths and river pattern are observed for the successive paleochannel generations. Our results clearly reflect at least three different geomorphic and hydrological periods in the evolution of the fluvial system since the late Pleistocene. Changes in discharge and sediment load may be controlled by combinations of two interrelated mechanisms: (i) spatial changes and re-organizations of the drainage network in the upper catchment, and/or (ii) climate changes with their associated local to catchment-scale modifications in vegetation cover, and changes in discharge, inundation frequencies and magnitudes, which have likely affected the evolution of the fluvial 2 system in the Llanos de Moxos. In summary, our study has revealed the enormous potential which geomorphic mapping and analysis combined with luminescence based chronologies hold for the reconstruction of the late Pleistocene to recent fluvial system in a large portion of Amazonia.

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“…The Beni and the Mamoré are characterized by high sedimentary loads, high meandering rates, and increasing discharge downstream (Aalto et al, 2003;Constantine et al, 2014;Guyot et al, 1996). They do not form logjams and they undergo avulsions on a millennial scale, mostly driven by neotectonic events and/or changes in climate (Dumont and Fournier, 1994;Lombardo, 2014;Plotzki et al, 2013). In contrast, their smaller tributaries often show downstream decreases in discharge, which is accompanied by the frequent formation of crevasses that often evolve into complete river avulsions (Lombardo, 2016).…”

Section: Discussionmentioning

confidence: 99%

River logjams cause frequent large-scale forest die-off events in southwestern Amazonia

Lombardo

2017

Earth Syst. Dynam.

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Abstract. This paper investigates the dynamics of logjam-induced floods and alluvial deposition in the Bolivian Amazon and the effects these have on forest disturbance and recovery cycles. It expands on previous work by Gullison et al. (1996) who reported a case of catastrophic floods triggered by logjams in the Chimane Forest in the Bolivian Amazon. No further studies have followed up on this observation and no research has been published on the effects of large wood in tropical lowland rivers. The study is based on the analysis of a time series of Landsat imagery and field evidence. Results show that logjam-induced floods are a major driver of forest disturbance along the Andean piedmont in the Bolivian Amazon. New logjams form on an almost yearly basis, always further upriver, until an avulsion takes place. Logjam-induced floods are characterized here by the sudden deposition of a thick sand layer and the death of forest in a V-shaped area. The Bolivian Amazon offers a unique opportunity for further research on how large wood affects river behavior in lowland tropical settings and how large and frequent forest disturbance events resulting from river logjams affect forest biodiversity and community successions.

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

Cited by 18 publications

References 66 publications

Neotectonics, flooding patterns and landscape evolution in southern Amazonia

Neotectonics, flooding patterns and landscape evolution in southern Amazonia

Geomorphology and evolution of the late Pleistocene to Holocene fluvial system in the south-eastern Llanos de Moxos, Bolivian Amazon

River logjams cause frequent large-scale forest die-off events in southwestern Amazonia

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