Caracterização da ocorrência de padrões de sonar de varredura lateral e sísmica de alta freqüência (3,5 e 7,0 kHz) na porção sul da Baía de Guanabara - RJ

Quaresma, Valéria da Silva; Dias, Gilberto T. M.; Neto, José Antônio Baptista

doi:10.1590/s0102-261x2000000200008

Cited by 49 publications

(34 citation statements)

References 1 publication

(1 reference statement)

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“…The hydrodynamic conditions in the Guanabara Bay are described and discussed by several authors that correlated them with the distribution of sediments (Amador, 1992;Quaresma, 1997;Quaresma et al, 2000;Catanzaro et al, 2004).…”

Section: Study Areamentioning

confidence: 99%

High-Resolution Acoustic Mapping of Gas Charged Sediments and Living Benthic Foraminifera Assemblages From the Ne Region of the Guanabara Bay (Rj, Brazil)

et al. 2016

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. 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

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Section: Study Areamentioning

confidence: 99%

High-Resolution Acoustic Mapping of Gas Charged Sediments and Living Benthic Foraminifera Assemblages From the Ne Region of the Guanabara Bay (Rj, Brazil)

et al. 2016

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“…Reference [5] also described a reflexive echo type associated with sandy sediments. According to these authors, this type of acoustic answer came from areas where the hydrodynamics or the sea bottom gradient is higher.…”

Section: Resultsmentioning

confidence: 99%

“…Recognizing the importance of the physical and acoustic properties of marine sediments, many studies utilize echo-characters to understand the late Quaternary sedimentation processes in Southeastern Brazilian shelf. Marine high resolution seismic profiles also have been used to identify geomorphologic features, characterize sediment types and understand sedimentary processes [3], [4], [5]. The western boundary upwelling system (WBUS) off Cabo Frio (23 o S) is located in the southeastern Brazilian continental shelf (Fig.…”

Section: Introductionmentioning

confidence: 99%

Echo-character identification and grain size analysis of the upwelling system of Cabo Frio, RJ

Gomes

Mendoza

Albuquerque

et al. 2013

2013 IEEE/OES Acoustics in Underwater Geosciences Symposium

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The acoustic patterns variation can be used to understand the sediment distribution extrapolating the information to places where is not possible to take any sample. Many authors already use this integrated method to investigate interest areas in, both, commercial and scientific aspect. In this direction the current study initiated in 2009 in the frame of the Geochemistry Network PETROBRAS/CENPES, aims to track the quaternary evolution of a muddy bank situated at the coastal western boundary upwelling system (WBUS) off Cabo Frio (23 o S) in the Atlantic Ocean. The WBUS is located at the north coast of the Rio de Janeiro State, Brazil. Here the coastline orientation differs from the default East-West direction of the Brazilian coast, concomitant with the boundary of the Campos and Santos Basins, the most important oil and gas basins of the country. The upwelling phenomenon occurs due to constant northeast winds. The same winds combined with the NortheastSouthwest coastline orientation also promote a curl confluence making the environment even more complex. Seismic data was acquired in cruises on board the RV Ocean Survey. Altogether 680 km was covered by a 3.5 KHz sub-bottom using the Geopulse Geoacustic System. Further, four piston cores were collected to be scan and described in physic parameters and sedimentological content, respectively. The scan was performed using a Geotek Multi Sensor Core Logger (MSCL), which measure and register the Vp, gamma density and porosity of the core. After the scan, the cores were sample and analyzed on sedimentological grain size distribution determined by a Cilas 1064 laser analyzer. The results were integrated in order to identify common trends. Three major echo-characters were described in seismic records. Grain size analysis presented a good relationship with these echos. Echo A) Transparent, represented by a sharp bottom reflector with no sub-bottom reflectors scatter of a transparent layer mapped in seismic records. The grain size distribution is more balanced with a slight higher content of sands (55 %) in the correspondent core. Echo B) Stratified described as a series of parallel sub-bottom horizons, its percentage of clays is the highest of the three cores (77 %). The last echo, C) Reflexive, is a prolonged echo with one or none subbottom reflector. This echo is related to the highest percentage of sands of the three cores (61%). The sediment analysis was extrapolated all over the echo-characters extension to understand the transport regime over the area. This criteria, allied to isopach map, made possible to recognize three distinct zones inside the muddy accumulation.

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“…In Brazil, the presence of these features has been described by various authors such as VITAL and STATTEGGER (1997) in the lowest stretch of the Amazon River; FIGUEIREDO and NITTROUER (1995) and FIGUEIREDO et al (1996) in the Amazon submarine delta and COSTA and FIGUEIREDO (1998) on the Amazon Continental Shelf; BAPTISTA NETO et al (2011) in Rodrigo de Freitas Lagoon -Rio de Janeiro; BENITES et al (2015) in Saco do Mamangua, Rio de Janeiro; BAPTISTA NETO et al (1996), QUARESMA et al (2000) and CATANZARO et al (2004) in Guanabara Bay, Rio de Janeiro; WESCHENFELDER et al (2006) in Patos Lagoon -Rio Grande do Sul associated with low-lying paleotopographical features such as paleo river channels and/or valleys; SCHWARZER et al (2006) in the Rio Açu Canyon and FRAZÃO and VITAL (2007) in the Potengy estuary, both in Rio Grande do Norte; FÉLIX (2012) in the Bertioga Channel, São Paulo;andSOUZA et al (2011), DEMARCO et al (2012), GUESSER et al (2012) andWESCHENFELDER et al (2016) presented preliminary results for the North Bay and the Conceição Lagoon -on the Santa Catarina Coast (Figure 1). In summary, gas-charged sediment and exhaust gases escaping into the water column occur in Brazil on the continental shelf and in rivers, bays and lagoon systems, from north to south, normally associated with sediments rich in organic matter.…”

Section: Introductionmentioning

confidence: 89%

Shallow gas seismic structures: forms and distribution on Santa Catarina Island, Southern Brazil

et al. 2016

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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.

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Caracterização da ocorrência de padrões de sonar de varredura lateral e sísmica de alta freqüência (3,5 e 7,0 kHz) na porção sul da Baía de Guanabara - RJ

Cited by 49 publications

References 1 publication

High-Resolution Acoustic Mapping of Gas Charged Sediments and Living Benthic Foraminifera Assemblages From the Ne Region of the Guanabara Bay (Rj, Brazil)

High-Resolution Acoustic Mapping of Gas Charged Sediments and Living Benthic Foraminifera Assemblages From the Ne Region of the Guanabara Bay (Rj, Brazil)

Echo-character identification and grain size analysis of the upwelling system of Cabo Frio, RJ

Shallow gas seismic structures: forms and distribution on Santa Catarina Island, Southern Brazil

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