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Clemente, I.M.M.M.; da Silva, F.S.; Laut, L.L.M.; Frontalini, F.; da Costa, V.L.; da Conceiçã o Rodrigues, M.A.; Pereira, E.; Bergamaschi, S.; Filho, J.G.M., and Martins, M.

. High-resolution acoustic mapping of gas charged sediments and living benthic foraminifera assemblages from the NE region of the Guanabara Bay (RJ, Brazil). Journal of Sedimentary Environments, 1 (3): 360-384. AbstractThis work was performed in the NE region of the Guanabara Bay, a highly impacted Brazilian coastal system, located in Rio de Janeiro State. It aimed to: i) identify and map the areas with occurrence of gas in the sediment, as well as its acoustic signature; ii) characterize the physical properties of the sediments and; iii) document the response of microbenthic organisms (living benthic foraminifera) to changes in quantity and quality of organic matter. Seismic surveys at the frequency of 12 kHz identified a large area with about 50% gas charged sediments in the study area.The main acoustic signatures of the shallow gas were black shadow and gas blanket. In addition, features related to gas seepages to the water column (acoustic plumes and pockmarks) and gas percolation within the sediments (intrasedimentary plumes, turbidity pinnacles) were also identified. The gas has a biogenic origin and results from the high acumulation rate between 0.03 to 0.9 cm.year -1 and from the decomposition of large amount of organic matter (10-20%). Vertical distribution of gas ranges from few centimeters to 9 m below the water-sediments interface. These occurrences are related to both gas migration from lower sedimentary layers to Holocene muds above, and to recent generation in near-surface sediments as the area display favorable conditions for gas production. Cores ranging from 150-240 cm in length have predominantly muddy sediments and variations in the P-wave velocity followed the changes in sediment density, controlled mainly by the presence of gas in sediments, bioclasts accumulation, textural variation and percentage of organic matter. Journal of Sedimentary Environments

Multiproxies (benthic foraminifera, ostracods and biopolymers) approach applied to identify the environmental partitioning of the Guadiana River Estuary (Iberian Peninsula).

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