Late cenozoic history of the eastern llanos of venezuela: Geomorphology and stratigraphy of the Mesa Formation

Carbon, Jan‐Mathieu; Schubert, Carlos

doi:10.1016/1040-6182(94)90023-x

Cited by 10 publications

(5 citation statements)

References 9 publications

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“…The floodplain of the Mapire river is located in SE Venezuela, between 7°30 0 -8°30 0 N and 64°30 0 -65°00 0 W. This river is a north tributary of the lower Orinoco river, and its basin constitutes a region of low relief covered by the Pleistocene Mesa Formation, which consists of horizontally bedded alluvial sediments and to a minor extent by marsh deposits (Carbón and Schubert 1994).…”

Section: Study Areamentioning

confidence: 99%

Seasonal changes in soil phosphorus dynamics and root mass along a flooded tropical forest gradient in the lower Orinoco river, Venezuela

et al. 2008

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The effects of natural hydrological fluctuations on the nature and bioavailability of soil phosphorus (P) in relation to iron (Fe) and aluminum (Al) chemistry and root mass were studied along a flooded tropical forest gradient in Mapire river, Venezuela. Soil samples were collected following a complete natural hydroperiod: end of the dry season (May 2004), end of the rainy season (November 2004) and end of the subsequent dry season (May 2005), and from three zones subjected to different flooding intensities: MAX, MED and MIN zones inundated for 8, 5 and 2 months per year respectively. The results showed that flood induced the increase of resin-Pi in the MAX zone, but not in the MED and MIN zones. Flood in the soil of the MAX zone also induced the increase of the NaOH-Pi fraction, which removes inorganic P sorbed onto secondary Fe and Al minerals. Changes in this redox-sensitive P form can be considered indirect evidence that P in the MAX zone can be released from the dissolution of iron oxyhydroxide. This field study also showed that along the flooded forest gradient, fine root mass declined during the flood event. However, such decline was more pronounced in the MIN zone than in the MAX zone. In this zone fine root mass was higher than in the other zones.

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Section: Study Areamentioning

confidence: 99%

Seasonal changes in soil phosphorus dynamics and root mass along a flooded tropical forest gradient in the lower Orinoco river, Venezuela

et al. 2008

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“…This zone is located at the south of the Anzoátegui and Monagas states, and is formed by consolidated and partly unconsolidated sediments from the actively uplifting mountain belts to the north and west of the Orinoco basin (González de Juana et al, 1980). The Mesa formation, constituted during Pleistocene (Carbón and Schubert, 1994), has a maximum relief less than 200 m and consists of horizontally bedded alluvial sediments, represented by light gray, coarse grained quartz sand, with cross-bedding marked by ochre, red and pink alteration, and gravels cemented with ferruginous material (González de Juana et al, 1980). The typical topography consists of mesas north of the left margin of the Orinoco River.…”

Section: Introductionmentioning

confidence: 99%

Survey of trace metals in drinking water supplied to rural populations in the eastern Llanos of Venezuela

Mora¹,

Mac-Quhae²,

Calzadilla³

et al. 2009

Journal of Environmental Management

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“…The floodplain of the Mapire River is located in SE Venezuela, between 7°30¢-8°30¢ N and 64°30¢-65°00¢ W. This river is a northern tributary of the lower Orinoco River, and its basin constitutes a region of low relief covered by the Pleistocene Mesa Formation, which consists of horizontally bedded alluvial sediments and to a minor extent by marsh deposits (Carbo´n and Schubert 1994).…”

Section: Study Areamentioning

confidence: 99%

Implications of soil organic carbon and the biogeochemistry of iron and aluminum on soil phosphorus distribution in flooded forests of the lower Orinoco River, Venezuela

et al. 2005

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Relationships among soil phosphorus distribution, soil organic carbon and biogeochemistry of iron and aluminum were studied along a flooded forest gradient of the Mapire river, Venezuela. Soil samples were collected during the dry season in three zones subjected to different flooding intensity: MAX inundated 8 months per year, MED inundated 5 months per year, and MIN inundated 2 months per year. Total labile phosphorus (resin + bicarbonate extractable fractions) was significantly higher in MIN than in MAX. The longer non-flooding period in MIN probably allowed a higher accumulation of microbial biomass in soils of this zone and consequently a greater release of the bicarbonate organic fraction. The moderately labile phosphorus fraction associated with the chemisorbed phosphorus on amorphous and some crystalline aluminum and iron was significantly lower in MAX than in MIN following the same tendency observed for crystalline iron oxides. This result allowed us to hypothesize that the combined effect of a long flood period and a high soil organic carbon content in the MAX, could be appropriate conditions for microbial reduction of stable forms of iron. The ratio of soil organic carbon to total organic phosphorus decreased from MAX to MIN, indicating higher mineralization of organic phosphorus in MIN. Our results suggests two distinct flood-dependent mechanisms operating for phosphorus release along the gradient. In MAX mineralization process appears to be limited, while microbial mineral dissolution appears to be an important source of phosphorus. In MIN supply of phosphorus is associated with the stability of soil organic matter.

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Late cenozoic history of the eastern llanos of venezuela: Geomorphology and stratigraphy of the Mesa Formation

Cited by 10 publications

References 9 publications

Seasonal changes in soil phosphorus dynamics and root mass along a flooded tropical forest gradient in the lower Orinoco river, Venezuela

Seasonal changes in soil phosphorus dynamics and root mass along a flooded tropical forest gradient in the lower Orinoco river, Venezuela

Survey of trace metals in drinking water supplied to rural populations in the eastern Llanos of Venezuela

Implications of soil organic carbon and the biogeochemistry of iron and aluminum on soil phosphorus distribution in flooded forests of the lower Orinoco River, Venezuela

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