Abstract This work consists of the sedimentological, mineralogical, and geochemical characterization of eight marine sediment cores collected in the Central Bransfield Basin, along a transect between the South Shetland Islands to the Antarctic Peninsula and its correlation to the sedimentary and oceanographic processes of the area. A chemical characterization based on X-ray fluorescence dispersive spectrometry was implemented to obtain geochemical data of the marine sediment while the minerals were identified by X-ray diffraction. The study allowed to classify the cores into three groups according to their sediment source and chemical and mineralogical characteristics. The joint assessment of the geochemical and mineralogical signature of the sediment has confirmed that the elemental ratios Ti/Ca and Fe/Ca can be applied as proxies in the reconstitution of the terrigenous contribution to the Central Bransfield Basin if we consider the sedimentary contribution of the volcanic edifices present in the region. The Fe/K ratio associated with the Chemical Index of Alteration reinforced an increase in the degree of weathering near South Shetland Island, which is also pointed out by other authors in studies on climate change mainly in the subantarctic islands. The trend of temperature increase implies the importance of monitoring the region. sedimentological area Xray X ray diffraction characteristics TiCa Ti Ca FeCa Fe region FeK K Island islands

Abstract This research aims to investigate sediment cores from a glaciomarine environment based on their petrophysical parameters to elucidate lithological and sedimentary issues, as well as to identify a geophysical signature based on their parameter’s response. To achieve this objective, six marine sediment cores were collected in the Central Bransfield Basin - Antarctica, the lengths ranging from 1.5 to 5.2 meters in water depths ranging from 304 to 1463 meters. The cores were submitted to different analyses and values from density, magnetic susceptibility, electrical resistivity, p-wave velocity, total gamma radiation, silt, clay and sand contents, and mean grain size for each core location were considered. Four large lithologies were identified according to their geological and geophysical characteristics. The first group is subglacial deformation till (GC16); the second is massive diamicton (GC13 and GC12), the third group is composed of diamictons from the basin (AM10) and lower slope (GC09); the fourth lithological group is composed of siliceous mud from an upper slope location (GC06A). The characteristics recorded across Central Bransfield Basin (from South Shetlands Islands to Antarctic Peninsula) highlighted the relationship between the lithological content and associated depositional processes with the geophysical proprieties as density and magnetic susceptibility.

Abstract 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.

Resumo Este artigo apresenta a distribuição espacial das estruturas de gás raso e as classifica com base em dois conjuntos de dados de registros sísmicos diferentes com o CHIRP, um na Lagoa da Conceição (CL) e o outro na Baía Norte (NB), ambos na Ilha de Santa Catarina, sul do Brasil. Os dados de sonar de varredura lateral da CL foram usados para facilitar a interpretação. Os dados sísmicos de subsuperfície (SB) foram processados e interpretados por meio do software SeisPrho e os dados obtidos com o sonar de varredura lateral (SSS), pelo software SonarWiz5. A medida espacial foi realizada por intermédio de GIS. As estruturas de gás raso foram definidas de acordo com as formas apresentadas nos registros sísmicos (eco-caráter). Na CL, as acumulações rasas de gás foram encontradas sob a forma de escapes nas exsudações e feições apresentando estruturas de gás superficial, entre a superfície e 8,20 ms (cerca de 12,3 m). Estas acumulações de gás foram encontradas na forma de Cobertura Acústica com Plumas Acústicas associadas, além de Sombra Negra. As pockmarks foram observadas no fundo da lagoa, ligadas aos escapes de gás (diâmetro médio de 0,97 ± 0,19 m e densidade de 54 a 242 unidades por 50 m2). Na NB observou-se três tipos de estruturas de gás raso no perfil sísmico, ou seja, de Cobertura Acústica, Pináculos de Turbidez e Plumas Intrssedimentares. A profundidade variou da superfície até 12,10 ms (cerca de 18,15 m). Em ambos os ambientes, o gás é expelido a partir do sedimento para a coluna de água. As pockmarks na CL e na NB, as feições de pluma acústica e os sedimentos ricos em enxofre total validam essa evidência.

Abstract This paper presents the spatial distribution of shallow gas structures and classifies them on the basis of two different data sets of CHIRP seismic records, one from the Conceição Lagoon (CL) and the other from North Bay (NB), both on Santa Catarina Island, Southern Brazil. Side scan sonar data from the CL were used to facilitate the understanding. The sub bottom (SB) seismic data were processed and interpreted by means of the SeisPrho software, the side scan sonar (SSS) data by SonarWiz5 software and the spatial extension being measured with the help of GIS. The shallow gas structures were defined in accordance with their shapes in the seismic recordings (echo-character). At the CL, shallow gas accumulations were found in the form of seepages and features presenting shallow gas structures between the surface and 8.20 ms (around 12.3 m). Accumulations of gas were found in the form of Acoustic Blanking with Acoustic Plume, and also Black Shadows. Pockmarks were found on the lagoon floor and associated with gas seepages (average size diameter 0.97 ± 0.19 m and density from 54 to 242 units per 50 m2). In the NB three types of shallow gas features were found in the seismic profile, namely Acoustic Blanking, Turbidity Pinnacles and Intra-sedimentary plumes. The depth varied from the surface to 12.10 ms (around 18.15 m). In both environments, the gas is escaping from the sediment into the water column. The Pockmarks in the CL and the Acoustic Plume features and sediment rich in total sulfur in the NB validate these findings.

Este trabalho combina informações obtidas por testemunhos de sondagem com dados adquiridos por perfilagem geofísica a fim de verificar a influência dos parâmetros geológicos e sedimentológicos na velocidade de ondas P em sedimentos marinhos superficiais. Dados de velocidade da onda compressional (Vp), densidade gama, impedância acústica e susceptibilidade magnética foram correlacionados com dados geológicos de quatro testemunhos coletados na zona costeira da cidade de Caravelas, estado da Bahia. As propriedades geofísicas foram obtidas utilizando como sistema de medição o perfilador multisensor de testemunhos (MultiSensor Core Logger - MSCL). Os testemunhos foram descritos segundo a geologia, cor e grau de compactação. Oito tipos distintos de sedimentos foram observados: conchas, areia grossa a muito grossa, areia média, areia muito fina a fina, lama arenosa, lama compacta, lama fluida e lama muito fluida. Os resultados mostram que, de maneira geral, os maiores valores de velocidade e densidade, inversamente proporcionais aos de susceptibilidade magnífica, estão associados aos sedimentos de maior granulometria. Os valores de Vp para areia muito grossa e conchas mostrou-se errático devido a falta de compactação desses materiais. Os gráficos de impedância acústica e do coeficiente de reflexão facilitaram a identificação de interfaces e apresentaram coerência em relação aos perfis de velocidade e de densidade. Medições de granulometria foram realizadas na seção de lama arenosa do testemunho JP-112, para ratificar a relação da variabilidade dos parâmetros físicos com a classificação granulométrica utilizada para a caracterização dos quatro testemunhos.

This research combines geological data obtained from core samples and geophysical properties in order to investigate how geological and sedimentological parameters affect the velocity of P-waves in near surface marine sediments, The velocity of P-waves (Vp), gamma density, acoustic impedance and magnetic susceptibility were correlated with core geology of four core of the coastal region of Caravelas, Bahia State. Geophysical properties were acquired using the MSCL (MultiSensor Core Logger). Core were opened and described according to grain size, color, compaction degree. Eight different kinds of sediments were recognized: shell, coarse to very coarse sand, medium sand, fine to very fine sand, sandy mud, compact mud, fluid mud, and very fluid mud. The results showed that, in general, the highest values of Vp and density and the lowest values of magnetic susceptibility are related to the coarser sediments. Very coarse sediments and shells showed erratic values basically due to the low compaction of these materials. The acoustic impedance and reflection coefficient profiles were useful to detect sediments interface. More detailed grain size analysis were conducted at the sandy mud section of core JP-112 and corroborated the relationship between Vp and grain size.

O presente trabalho descreve os resultados da compilação de dados geológicos e geofísicos, realizados na margem continental norte brasileira, publicados em artigos científicos e dissertações de mestrado, associados à aquisição de novos dados sísmicos de alta resolução, a fim de avaliar o estado-da-arte do conhecimento geológico da região em termos de ecofácies e sua relação com a geologia do fundo marinho. Os resultados mostram que os mapas de distribuição superficial dos sedimentos da região, não refletem com precisão a diversidade de ecofácies observadas nos registros de sub-bottom profiler, tanto na plataforma como no talude continental. Este fato indica que os processos geológicos atuantes durante a deposição do sedimento, que lhes confeririam características físicas particulares independente do tipo de sedimento, estariam também refletidos nessa diversidade de ecofácies.

The present work describes the results from the compilation of geological and geophysical data, associated to the acquisition of new high-resolution seismic data, in order to identify the actual knowledge about the geology of the northern Brazilian continental margin. The results show that the known superficial distribution of sediments does not reflect the diversity of echo-characters observed on sub-bottom profiler data, suggesting that these are also sensitive to the geological processes acting during sedimentation.

Este artigo é uma introdução sobre algumas técnicas geofísicas acústicas que podem ser usadas na pesquisa aplicada a mineração submarina. O sonar de varredura lateral, assim como a perfilagem sísmica de alta resolução são métodos geofísicos acústicos que permitem a investigação da distribuição superficial de sedimentos no fundo do mar e a identificação de estruturas geológicas sub-superficiais e camadas sedimentares com potencial para exploração mineral. Os dois métodos usam a propagação e reflexão de ondas acústicas através da coluna d'água e das camadas sedimentares a medida que estas ondas passam de um meio para o outro A quantidade de energia que é refletida pela interface depende de diversos fatores tais como ângulo de incidência, impedância acústica e rugosidade do fundo do mar. Através da amplitude do sinal de retorno é possível classificar diferentes tipos de sedimentos correlacionando a intensidade do eco com a dureza da cobertura sedimentar do fundo do mar. É este sinal que carrega informações sobre a geologia do fundo do mar. Estas informações são muito importantes na avaliação do potencial mineral de uma área de interesse.

This paper gives an introduction about some acoustical geophysical techniques that can be used in the marine mineral exploration. The side scan sonar and reflection seismic are acoustic tools that allow the investigation of the sediment distribution on the seafloor as well as the identification of subsurface geological structures and sedimentary layers that favors mineral concentration. Both methods use the propagation and reflection of acoustic waves through the water column and the sedimentary sequence as the waves pass from one medium to another. The amount of seismic energy that is reflected depends on several different factors such as incidence angle, acoustic impedance and roughness of the seafloor. With the amplitude of the signal it is also possible to classify different kinds of sediments correlating the echo strength with hardness of the seafloor. It is this signal that carries information about the geology of the seafloor. These informations are very important for the evaluation of the mineral potential of a given area.