scholarly journals Palynofacies, environments, and climate changes in the Magdalena River Basin

2021 ◽  
Author(s):  
M. A. Lorente
Keyword(s):  
Grain Size ◽  
Organic Matter ◽  
River Basin ◽  
Grass Pollen ◽  
Amorphous Materials ◽  
Particle Morphology ◽  
Bimodal Distribution ◽  
Ice Age ◽  
Palynological Assemblages ◽  
Magdalena River

ABSTRACTFour environments (swamp, shallow lake, alluvial flood plain, and lagoon) from the Lower Magdalena River Basin were studied for palynofacies’ quantitative characterization. Each environment has been described based on four criteria: palynomorph assemblage, organic matter concentration, organic matter palynological composition, and organic particle morphology.Shallow lakes’ palynological assemblages are dominated by composite and grass pollen. The POM (particulate organic matter) morphology is characterized by a maximum at Φ 5 class (silt), and it has a sphericity histogram with bimodal distribution (peaks at 0.1 and 0.5/0.6). From a composition point of view, POM is mainly opaque amorphous materials. POM concentration is usually lower than 0.1%.Swamp environments palynological assemblages are dominated by grass pollen with a slightly smaller amount of composite pollen. The POM is dominated by finely dispersed amorphous and indeterminate “other” types (organo-mineral gel ?), depending on the oxidation degree. The swamp concentration of organic matter a few centimeters below the water-sediment interface varies between 0.1% and 0.3%. Below that, organic concentration is usually lower than 0.1%.Lagoon assemblages are rich in species and specimens, but assemblages are highly variable. Main components are either finely dispersed amorphous or plant cuticular/epidermal or amorphous homogeneous and heterogeneous or fungal remains. Peat lithology is rich in mangrove pollen, while clay assemblages are dominated by composites, grass, and water plants together with Botryococcus algal remains. Lagoon sediments are the richest in POM concentration, with values between 0.13% and 1% (excluding peats). Regarding particle size and shape, in this environment, they show a trend to decrease in grain size from Φ 1 to Φ 2 class (sand) dominated assemblages to Φ 5 to Φ 6 class (silt) dominated assemblages from base to top. Elongated shapes are abundant, with 30% to 50% of particles in the tabloid to elongated tabloid classes.Alluvial - fluvial flood basin samples are often barren in palynomorphs and organic matter. Occasionally present grass pollen and fungal remains. The POM, when present, is mainly of organo-mineral gel type and has a bimodal grain size distribution, with a minor peak at Φ 7 class (v.f.silt) and a major peak at Φ 4 to Φ 2 class (c. silt to f. sand).Significant changes in quantitative palynofacies occur within the top few meters of the cores, representing the last 1000 yr of sedimentation in the area. These changes are related to shifts in climate, from colder to warmer conditions or from dry to wet periods, most probably linked with E.N.S.O. A short dry and cold period related to the “Little Ice Age” was identified in the Ayapel and Cienaga de El Medio cores.

scholarly journals SEDIMENTOLOGIA DE LAGUNAS COSTERAS: CIENAGA GRANDE DE SANTA MARTA Y CIENAGA DE PAJARALES

2016 ◽  
Vol 25 ◽  
Author(s):  
Gladys Bernal ◽  
Julliet Betancur
Keyword(s):  
Grain Size ◽  
Organic Matter ◽  
Chemical Analysis ◽  
X Ray Diffraction ◽  
Caribbean Coast ◽  
X Ray ◽  
Deltaic Plain ◽  
Magdalena River

Ciénaga Grande de Santa Marta and Ciénaga de Pajarales are the two main lagoons of the marginal lagunar system at the deltaic floodplain of Magdalena river, Caribbean coast of Colombia. A systematic surficial sampling was carried out in such lagoons and Salamanca coast. A sporadic sampling was done in other places of the deltaic plain. This paper presents results about grain size, mineralogy, organic matter contents, CaCOa contents, X ray diffraction and chemical analysis of salts for sediments. Sedimentologic charts, distribution schemes and provenience notes are presented.

scholarly journals The Rise of Climate-Driven Sediment Discharge in the Amazonian River Basin

Atmosphere ◽  
2020 ◽  
Vol 11 (2) ◽  
pp. 208 ◽  
Author(s):  
Nazzareno Diodato ◽  
Naziano Filizola ◽  
Pasquale Borrelli ◽  
Panos Panagos ◽  
Gianni Bellocchi
Keyword(s):  
River Basin ◽  
Amazon Basin ◽  
Global Climate ◽  
Climate Extremes ◽  
Temporal Variations ◽  
Sediment Discharge ◽  
Storm Events ◽  
Discharge Data ◽  
Magdalena River ◽  
Sediment Export

The occurrence of hydrological extremes in the Amazon region and the associated sediment loss during rainfall events are key features in the global climate system. Climate extremes alter the sediment and carbon balance but the ecological consequences of such changes are poorly understood in this region. With the aim of examining the interactions between precipitation and landscape-scale controls of sediment export from the Amazon basin, we developed a parsimonious hydro-climatological model on a multi-year series (1997–2014) of sediment discharge data taken at the outlet of Óbidos (Brazil) watershed (the narrowest and swiftest part of the Amazon River). The calibrated model (correlation coefficient equal to 0.84) captured the sediment load variability of an independent dataset from a different watershed (the Magdalena River basin), and performed better than three alternative approaches. Our model captured the interdecadal variability and the long-term patterns of sediment export. In our reconstruction of yearly sediment discharge over 1859–2014, we observed that landscape erosion changes are mostly induced by single storm events, and result from coupled effects of droughts and storms over long time scales. By quantifying temporal variations in the sediment produced by weathering, this analysis enables a new understanding of the linkage between climate forcing and river response, which drives sediment dynamics in the Amazon basin.

Evidence of river flow regulation loss over time in the Magdalena river basin 

2021 ◽  
Author(s):  
Diver E. Marín ◽  
Juan F. Salazar ◽  
José A. Posada-Marín
Keyword(s):  
Climate Change ◽  
Environmental Change ◽  
River Basin ◽  
River Flow ◽  
Southern Oscillation ◽  
Scaling Theory ◽  
Scaling Properties ◽  
Low Flows ◽  
High Flows ◽  
Magdalena River

<p>Some of the main problems in hydrological sciences are related to how and why river flows change as a result of environmental change, and what are the corresponding implications for society. This has been described as the Panta Rhei context, which refers to the challenge of understanding and quantifying hydrological dynamics in a changing environment, i.e. under the influence of non-stationary effects. The river flow regime in a basin is the result of a complex aggregation process that has been studied by the scaling theory, which allows river basins to be classified as regulated or unregulated and to identify a critical threshold between these states. Regulation is defined here as the basin’s capacity to either dampen high flows or to enhance low flows. This capacity depends on how basins store and release water through time, which in turn depends on many processes that are highly dynamic and sensitive to environmental change. Here we focus on the Magdalena river basin in northwestern South America, which is the main basin for water and energy security in Colombia, and at the same time, it has been identified as one of the most vulnerable regions to be affected by climate change. Building upon some of our previous studies, here we use data analysis to study the evolution of regulation in the Magdalena basin for 1992-2015 based on the scaling theory for extreme flows. In contrast to most previous studies, here we focus on the scaling properties of events rather than on long term averages. We discuss possible relations between changes in the scaling properties and environmental factors such as climate variability, climate change, and land use/land cover change, as well as the potential implications for water security in the country. Our results show that, during the last few decades, the Magdalena river basin has maintained its capacity to regulate low flows (i.e. amplification) whereas it has been losing its capacity to regulate high flows (i.e. dampening), which could be associated with the occurrence of the extremes phases of  El Niño Southern Oscillation (ENSO) and anthropogenic effects, mainly deforestation. These results provide foundations for using the scaling laws as empirical tools for understanding temporal changes of hydrological regulation and simultaneously generate useful scientific evidence that allows stakeholders to take decisions related to water management in the Magdalena river basin in the context of environmental change.</p>

scholarly journals Breeding sites of Culicoides pachymerus Lutz in the Magdalena River basin, Colombia

2010 ◽  
Vol 105 (2) ◽  
pp. 216-219 ◽  
Author(s):  
María Cristina Carrasquilla ◽  
Felipe Guhl ◽  
Yaneth Zipa ◽  
Cristina Ferro ◽  
Raúl Hernando Pardo ◽  
...  
Keyword(s):  
River Basin ◽  
Breeding Sites ◽  
Magdalena River

scholarly journals Taxonomic review of Colombian Parodon (Characiformes: Parodontidae), with descriptions of three new species

2011 ◽  
Vol 9 (4) ◽  
pp. 709-730 ◽  
Author(s):  
Alejandro Londoño-Burbano ◽  
César Román-Valencia ◽  
Donald C. Taphorn
Keyword(s):  
New Species ◽  
River Basin ◽  
Morphological Characters ◽  
Valid Species ◽  
Type Specimens ◽  
River Drainage ◽  
Distribution Maps ◽  
Maracaibo Basin ◽  
Three New Species ◽  
Magdalena River

We review species of Parodon Valenciennes, 1850 from the Magdalena, Cauca, Orinoco, Amazonas, Atrato and Caribbean-Guajira River basins of Colombia using meristic and morphological characters. We recognize eight valid species, five previously described: P. apolinari Myers, from the Orinoco River basin; P. buckleyi Boulenger and P. pongoensis (Allen) from the upper Amazon; P. caliensis Boulenger, from the upper Cauca River drainage; and P. suborbitalis Valenciennes, from Lake Maracaibo basin. Three new species are described: P. alfonsoi, from the lower Magdalena River drainage; P. magdalenensis, from the middle Magdalena and upper Cauca River drainages; and P. atratoensis, from the Atrato River basin. We redescribe Parodon suborbitalis using type specimens and topotypes, and designate lectotypes. A taxonomic key is included for identification of the species, as well as geographic distribution maps.

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