Retrabalhamento de Sedimentos em Bacias Glaciais da Península Fildes, Antártica (Reworking of Sediments in Glacial Basins of The Fildes Peninsula, Antarctica)

Carina Petsch, Rafaela Mattos Costa, Kátia Kellem da Rosa, Rosemary Vieira, Jefferson Cardia Simões

Resumo


A área exposta à frente de geleiras em retração sofre processos de retrabalhamento pela ação do vento, variação da temperatura e água líquida. Diante disso, o presente trabalho investigou o retrabalhamento de sedimentos em bacias de drenagem proglaciais e periglaciais e possíveis mudanças no relevo na península Fildes, ilha Rei George, Antártica. Foram analisadas a granulometria e morfoscopia de 11 amostras sedimentares coletadas em diferentes transectos em área proglacial da geleira e em duas áreas periglaciais. As amostras proximais à geleira mostram pouco retrabalhamento, predominando cascalhos, sedimentos angulosos e sem estrias. Os lagos e canais glaciofluviais nessa bacia de drenagem atuam na seleção do material encontrado a jusante, predominando areia, material subangular a arredondado e esfericidade média. Na área periglacial, na bacia do rio do Vento, predomina cascalho e material sedimentar anguloso nos setores a montante, evidenciando intemperismo físico; a jusante predomina areia e material arredondado e com alta esfericidade. Na bacia do rio Grande evidencia-se a presença de areia, material menos anguloso e mais esférico. Diante disso, se a geleira Collins continuar retraindo como nas últimas décadas, poderá haver maior retrabalhamento dos sedimentos pelo fluxo de água na zona proglacial. Para as duas bacias periglaciais, um aumento de temperatura do ar pode ocasionar maior quantidade de água de fusão da neve. Podem ocorrer mudanças ambientais como rebaixamento do relevo pela erosão e preenchimento das bacias por sedimentos provenientes das paredes das falésias e também transportados por canais de fusão da neve.

 

 

A B S T R A C T

The exposed area ahead of shrinking glaciers undergoes reworking processes by wind, temperature variation and liquid water action. Therefore, the present work investigated the reworking of sediments in proglacial and periglacial drainage basins and possible changes in the relief on the peninsula Fildes, King George Island, Antarctica. The granulometry and morphoscopy of 11 sedimentary samples collected in different transects, in the proglacial area and in two periglacial areas, were analyzed. The granulometry was  performed for the determination of the material textural and a morphoscopic analysis to obtain the roundness and sphericity index. The sediments proximal to the glacier show little reworking, predominating gravels, angular sediments and without striae. The lakes and glaciofluvial channels in this drainage basin act in the selection of the material found downstream, predominating sand, rounded subangular material and medium sphericity. In the periglacial area, in the Rio do Vento basin, gravel and angular sedimentary material predominate in upstream sectors, evidencing physical weathering; downstream sand and rounded material with high sphericity predominance. In the Rio Grande basin there is evidence of sand, less angular and more spherical material. In view of this, if the Collins glacier continues to retract as in the last decades, there may be greater reworking of sediments by the flow of water in the proglacial zone. For the two periglacial basins, an increase in the air temperature can cause a greater amount of snow melting water. There may be environmental changes such as lowering the relief by erosion and filling the basins with sediments from the walls of the cliffs and also transported by snow melting channels.

Keywords: glaciology; glacial basins; environmental changes.


Palavras-chave


glaciologia; bacias glaciais; mudanças ambientais.

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DOI: https://doi.org/10.26848/rbgf.v11.7.p2335-2350

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Revista Brasileira de Geografia Física - ISSN: 1984-2295

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