The two most important lateritization cycles in the Amazon region and their paleoecological importance

Costa, Marcondes Lima da

doi:10.1590/s0001-37652001000300014

Cited by 3 publications

(2 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Uplift and erosion exposed the Sete Lagoas Formation to post‐burial meteoric diagenesis and Miocene lateritization (Costa, ; Carmo & Vasconcelos, , ). Lateritization resulted in hydrolysis, oxidation and dissolution of detrital, authigenic, diagenetic and hydrothermal minerals.…”

Section: Economic Phosphoritementioning

confidence: 99%

Neoproterozoic peritidal phosphorite from the Sete Lagoas Formation (Brazil) and the Precambrian phosphorus cycle

et al. 2015

View full text Add to dashboard Cite

The Neoproterozoic Sete Lagoas Formation (ca 610 Ma) of the São Francisco Basin, Brazil, is a succession of siltstone, limestone and phosphorite. Phosphorite forms part of a previously unrecognized 150 to 200 m thick, unconformity bounded depositional sequence. Lithofacies stacking patterns indicate that deposition was punctuated by higher order fluctuations in base level that produced aggradational parasequences. These shallowing-upward cycles record the progradation of phosphate-rich intertidal flats over shallow subtidal deposits as accommodation filled. The presence of mudcracks, authigenic chert nodules, lack of coarse terrigenous clastics and the abundance of silt with fine, abraded quartz grains suggests accumulation along an arid coastline with significant aeolian input. Delivery of phosphorus adsorbed on aeolian Fe-(oxyhydr)oxide and clay is interpreted as having stimulated phosphogenesis in peritidal environments. Lithofacies associations indicate that windblown phosphorus promoted the establishment of cyanobacterial communities along the coast, which produced photosynthetic oxygen and the suboxic conditions necessary for the precipitation of authigenic carbonate fluorapatite. As in other Precambrian phosphatic systems, nearshore oxygen oases were a prerequisite for phosphorite accumulation because redox sensitive phosphogenic processes were pushed into the sediment to concentrate phosphorus. In more distal, anoxic environments phosphorite could not form because these biotic and abiotic processes were suspended in the water column, which cycled phosphorus in sea water rather than at the sediment-water interface. Such shallow-water phosphorite is unlike larger, younger Neoproterozoic-Phanerozoic phosphatic deposits inferred to have formed in deeper-upwelling related environments. The increasing size of phosphatic deposits through the latest Precambrian is interpreted as reflecting the progressive ventilation of the oceans during the Neoproterozoic Oxygenation Event, and resultant expansion of phosphogenic environments into distal settings. The widespread cycling of bioavailable phosphorus at the sea floor not only produced the first true phosphorite giants, but may have also been an important precondition for the evolution of multicellular animals.

show abstract

Section: Economic Phosphoritementioning

confidence: 99%

Neoproterozoic peritidal phosphorite from the Sete Lagoas Formation (Brazil) and the Precambrian phosphorus cycle

et al. 2015

View full text Add to dashboard Cite

show abstract

“…In turn, Acrisols in the region present evidence of argilluviation under natural conditions [ 10 ], demonstrating the clay migration process from the A horizon (eluvial) to the B horizon (illuvial), forming a subsurface textural B horizon (Bt). Lastly, it is common to find ferruginous concretions arising from Lateritic mantle in Acrisols and Ferrasols of the region [ 15 ], which may be found in degradation due to the current environmental conditions [ 16 ].…”

Section: Introductionmentioning

confidence: 99%

Pedogenetic processes in anthrosols with pretic horizon (Amazonian Dark Earth) in Central Amazon, Brazil

Macedo

Teixeira²,

Corrêa

et al. 2017

PLoS ONE

View full text Add to dashboard Cite

Anthrosols known as Amazonian Dark Earth (ADE) have borne witness to the intensification of sedentary patterns and the demographic increase in Central Amazon. As a result, a recurring pattern has been observed of mounds with ADE arising from domestic activities and the disposal of waste. The objective of this research was to demonstrate the relationship of these anthropic activities with pedogenetic formation processes of ADE in the municipality of Iranduba, Brazil. Disturbed and undisturbed soil samples were taken from two areas of ADE (pretic horizon) and from a non-anthropic pedon. Physical, chemical, micromorphological and SEM-EDS analyses were performed. The coarse material of the pretic horizons consisted predominantly of quartz, iron nodules, ceramics and charcoal fragments, and the fine material is organo-mineral. There was a direct relationship between the color of pretic horizons and the number of charcoal fragments. The thickness of the ADE results from the redistribution of charcoal at depth through bioturbation, transforming subsurface horizons into anthropic horizons. ADE presents granular microaggregates of geochemical and zoogenetic origin. Degradation of iron nodules is intensified in pretic horizons, promoting a reverse pedogenic process contributing to the xanthization process. Surprisingly the anthropic activities also favor clay dispersion and argilluviation; clay coatings on the ceramic fragments and in the pores demonstrate that this is a current process. Processes identified as contributing to ADE genesis included: i) addition of organic residues and ceramic artifacts (cumulization) with the use of fire; ii) mechanical action of humans, roots and macrofauna (bioturbation); iii) melanization of deeper horizons as a result of bioturbation; iv) argilluviation and degradation of iron nodules. This study offers new support to archaeological research in respect to ADE formation processes in Central Amazon and confirmed the hypothesis that ancient anthropic activities may trigger and/or accelerate pedogenetic processes previously credited only to natural causes.

show abstract

Challenges in the Construction of Highways in the Brazilian Amazonia Environment: Part I – Identification of Engineering Problems

Campelo¹,

Campos²,

Baia³

et al. 2022

Applied Methods in Design and Construction of Bridges, Highways and Roads - Theory and Practice

View full text Add to dashboard Cite

The construction of highways in the Brazilian Amazonia Region is always problematic, mainly because it involves environmental obstacles but also technical, economic, and natural challenges. The environmental issues concern the deforestation of the virgin forest and the resulting environmental impacts. The technical ones are related to the natural subgrade, formed by the geologically young alluvial soils that are plastic, being highly compressible or expansive, present in the vast Amazon Basin, whereas the economic issues refer to the final costs of inputs for the construction of the layers of the highway since granular soils and stony materials are located in limited areas that are distant from the work sites, given the geographic immensity of the Brazilian Amazonia. There is also the cost of purging low-bearing capacity soil from the natural subgrade of the highway. Added to all this are the issues of nature, which involve high annual rainfall and the hydrological regime of river flooding and ebbing, which induce the saturation of the pavement layers and the loss of the global geotechnical stability of the compacted earth embankment, respectively. This work points out the Engineering difficulties to be faced in road infrastructure works in the Brazilian Amazon.

show abstract

The two most important lateritization cycles in the Amazon region and their paleoecological importance

Cited by 3 publications

References 0 publications

Neoproterozoic peritidal phosphorite from the Sete Lagoas Formation (Brazil) and the Precambrian phosphorus cycle

Neoproterozoic peritidal phosphorite from the Sete Lagoas Formation (Brazil) and the Precambrian phosphorus cycle

Pedogenetic processes in anthrosols with pretic horizon (Amazonian Dark Earth) in Central Amazon, Brazil

Challenges in the Construction of Highways in the Brazilian Amazonia Environment: Part I – Identification of Engineering Problems

Contact Info

Product

Resources

About