There are several problems associated with core location and sediment deformation during the coring procedure. Geophysical investigation of the seafloor using acoustic systems, such as high-resolution seismic and single-beam sediment classification, provides a very cost-effective evaluation on the distribution of sedimentary environments. The present study investigates the relationship between acoustic impedance and geotechnical properties of shallow marine sediments from the Santos Basin, Brazil. A total of eight cores from different geological settings were collected and measurements of P-wave velocity (Vp), gamma density, mean grain size, void ratio, water content and shear strength were conducted. The results show that, despite different trends according to the sedimentary environment, the acoustic impedance correlates very well with all geotechnical parameters analyzed.

This study investigated the terrestrial and submarine geomorphology and glacial landform records in the Martel inlet (King George Island) using a multi-resolution topobathymetric data based on seismic, multibeam surveys and terrestrial satellite datasets (REMA DEM). Geomorphometric analysis provided glacial landforms and sedimentary processes interpretation. The submarine sector has a mean depth of 143 m, a maximum depth of 398 m, and most of it has a low slope (0°-16°). Steep slopes (>30°) are found along the mid-outer sectors transition area. The continental shelf was divided into inner fjord (49 m depth), middle fjord (119 m), and outer fjord (259 m), based on depth, elevation and slope. The topobathymetric digital model provides evidence of geomorphological contrasts between these zones in the fjord's seafloor and subaerial environments. A prominent morainal bank in the transition between the inner and middle parts marks the limit of a past stationary stage of the Dobrowolski-Goetel ice margin. Streamlined glacial lineations demonstrate an NE-SW past ice flow direction and a wet-based thermal regime. The combined analysis of submarine and subaerial landforms enable the understanding of the former glacier configuration and its deglaciation history.

Revista da Gest?o Costeira Integrada

The paper aims to reconstruct the fluctuations of Dobrowolski Glacier, a tidewater glacier located in the inner position of the Admiralty Bay (King George Island, Antarctica), from the Little Ice Age (1400-1700) until the present. Measurements of the glacier’s area and length were based on multitemporal satellite imagery and submarine glacial landforms. The glacier surface area variations between the Little Ice Age and 2014 A.D were estimated. Morainic banks and paleoglacial reconstructions provided evidence of fluctuations in the surface area of the glacier between PIG and 2014 AD. Therefore, four stages of analysis were established: Stage I (Part I) (1400 to 1700), Stage I (Part II) (1700 until the mid-20th century), Stage II (mid-20th century until the 1980s), Stage III (1980 to 2000), and Stage IV (2000 to 2020). The climate during the Little Ice Age triggered the last major glacial advance, and their grounding line position was recorded by an external and prominent morainic bank. After the major glacial advance position of the grounding line, the ice-margin has undergone higher retreat rates (stage I) as response to the warming trend and the loss of anchoring point. The stage II (Unit B) is recorded by distal and discontinuous morainal ridges and glacial lineations formed in the context of an active ice flow at a deeper point in the fjord. During stage III (Unit C) glacial lineations and steep slopes occur, while landforms are less preserved, revealing a fast shrinkage phase. Stage IV is characterized by discontinuous morainic ridges (Unit D), when the glacier presents the highest annual glacial area loss. Currently, the accelerated shrinkage may be linked to the loss of anchorage on seamounts (serving as pinning points) and increased warming. The U-shaped valley geometry has also influenced the glacier shrinkage processes and the redirection of glacial paleoflow during the last 300 years. The retreat rate to mid-20th century-2020 period is higher than Little Ice Age- mid-20th century period.

This work consists in characterizing the sedimentary distribution of the South Shetland Islands continental margin, Bransfield Strait, Antarctica, throughthe interpretation and correlation of high-resolution seismic profiles and geological samples. The analysis of echo-characters, seismic amplitudes and their correlationwith the collected samples, revealed five different echo types. Echo types I and II have good seismic resolution and are characterized by continuous sharp bottom echoeswith subparallel reflections. Echoes III and IV are characterized by diffuse and very prolonged bottom echoes with no subbottom reflectors. Echo V is associated withglacial deposits on the upper slope in response to deglaciation and transport of coarse grains in a muddy matrix and is characterized by diffraction hyperbolae. Theecho-characters showed good correlation with geological samples collected along the Bransfield Strait and bays of the King George Island, but the correlation with theseismic amplitude map was not as obvious. Echo I shows medium-high amplitudes and samples within its area of occurrence (AM-02 and AM-14) indicate silty sandand sandy silt, respectively. Echo II presents the lowest seismic amplitudes and the sample collected within its area (AM-17) shows approximately 90% mud content.Echoes III and IV, located on the shallowest portions of South Shetland’s continental margin, demonstrate medium-low amplitude values, and are related to samplesAM-01 and AM-04, both classified as sandy silt with approximately 35%sand. Keywords: Bransfield Strait, echo-characters, high-resolution seismic, sedimentary analysis. RESUMO. O presente trabalho consiste na interpretação integrada da sísmica de alta resolução e da amostragem geológica, a fim de caracterizar a geologia de fundona região da margem continental das Ilhas Shetland do Sul, Estreito de Bransfield, Antártica. A caracterização geológica foi realizada através da análise de ecocaráteres, mapas de amplitude sísmica e sua correlação com os sedimentos coletados. Cinco diferentes ecocaráteres foram identificados e classificados. Ecos I e II demonstramboa resolução e são caracterizados por ecos contínuos e nítidos com reflexões subparalelas. Ecos III e IV são caracterizados por ecos difusos, muito prolongados ecom ausência de refletores subparalelos. O Eco V está associado a depósitos glaciais no talude superior, em respostas ao degelo, e ao transporte de grãos grossos em uma matriz mais fina. Além disso, é caracterizado pela presença de hipérboles de difração. Os ecocaráteres mostraram boa correlação com os testemunhos geológicos coletados no Estreito de Bransfield e nas baías da Ilha Rei George, mas não apresentaram uma relação óbvia com o mapa de amplitudes. O Eco I possui amplitudes médio-altas e as amostras contidas em sua área (AM-02 e AM-14) indicam, respectivamente, um conteúdo de areia siltosa e silte arenoso. O Eco II apresenta os menores valores de amplitude com conteúdo de lama (argila + silte) de aproximadamente 90%, conforme a amostra AM-17. Os Ecos III e IV, localizados nas porções mais rasasda margem continental das Shetland do Sul, demonstram valores médio-baixos de amplitude e se relacionam às amostras AM-01 e AM-04, ambas siltes-arenosos com conteúdo de areia de aproximadamente 35%. Palavras-chave: Estreito de Bransfield, ecocaráteres, sísmica de alta resolução, análise sedimentar.