| Summary: | A comparative study of changes at deglaciation environments was carried out at Wanda and Ecology glaciers, King George Island, Antarctica, by examining erosion and depositional processes. Data for the reconstruction of deglaciation were based on geomorphological and aerial photograph interpretations, as well as on analysis of multi-yearspot satellite images. Subglacial processes were investigated by means of morphoscopic and granulometric analyses of sediments collected during the summer season, and co-variance between Ra (percentage of angular clasts) and C40 (percentage of clast radio c/a ≤ 0.4) indexes.These glaciers have been retreating rapidly since 1956, with no periods of expansion. However, it is possible to observe differences in both glaciers deglaciation processes. The Ecology glacier has lost 1.35 km2 , whereas the Wanda glacier only 0.64 km2 in five decades. The retreat of the Ecology glacier has been greater at the northern part of the proglacial zone; a low frontal moraine at the southern part indicates a recent glacier ice front stabilization. In the Wanda glacier, ice flow orientation has changed during different retreat phases, together withwith ice thickness decrease. The exposure of several landforms and proglacial deposits, such as flutes, kame terraces, morainic ridges, clast pavements, striated rocks and eskers all result from retraction. Abraded and subglacially transported sediments predominate at the deglaciation environment with meltwater. A large proportion of fine-grained sediments, striated rock surfaces, clast pavements, stoss and lee blocks, indicate that the two glaciers are wet based, having a temperate basal thermal regime. Um estudo comparativo da evolução dos ambientes de deglaciação foi realizado nas geleiras Wanda e Ecology, ilha Rei George, Antártica para a análise dos processos erosivos e deposicionais subglaciais destes ambientes. Os dados para a reconstrução da deglaciação resultam da interpretação geomorfológica e de fotogramas aéreos, juntamente com análise de ...
|
|---|