Evidences of early to late fluid migration from an upper Miocene turbiditic channel revealed by 3D seismic coupled to geochemical sampling within seafloor pockmarks, Lower Congo Basin

López, Michel; Cochonat, Pierre; Levaché, D.; Sermondadaz, G; Séranne, Michel

doi:10.1016/j.marpetgeo.2006.02.004

Cited by 77 publications

(58 citation statements)

References 54 publications

(61 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Hovland and Judd (1988) and Hovland et al (2002) provide a thorough review and size-based classification of pockmarks. Recently, 'trains' of pockmarks have been associated with underlying and dewatering submarine channels (Gay et al, 2003(Gay et al, , 2006a(Gay et al, , 2006bHeinio and Davies, 2009). …”

Section: Canyon-pockmark Associationmentioning

confidence: 99%

Two fundamentally different types of submarine canyons along the continental margin of Equatorial Guinea

Jobe

Lowe

Uchytil

2011

Marine and Petroleum Geology

165

View full text Add to dashboard Cite

Most submarine canyons are erosive conduits cut deeply into the world's continental shelves through which sediment is transported from areas of high coastal sediment supply onto large submarine fans. However, many submarine canyons in areas of low sediment supply do not have associated submarine fans and show significantly different morphologies and depositional processes from those of 'classic' canyons. Using three-dimensional seismic reflection and core data, this study contrasts these two types of submarine canyons and proposes a bipartite classification scheme.The continental margin of Equatorial Guinea, West Africa during the late Cretaceous was dominated by a classic, erosional, sand-rich, submarine canyon system. This system was abandoned during the Paleogene, but the relict topography was reactivated in the Miocene during tectonic uplift. A subsequent decrease in sediment supply resulted in a drastic transformation in canyon morphology and activity, initiating the 'Benito' canyon system. This non-typical canyon system is aggradational rather than erosional, does not indent the shelf edge and has no downslope sediment apron. Smooth, draping seismic reflections indicate that hemipelagic deposition is the chief depositional process aggrading the canyons. Intra-canyon lateral accretion 2 deposits indicate that canyon concavity is maintained by thick (> 150 m), dilute, turbidity currents. There is little evidence for erosion, mass wasting, or sand-rich deposition in the Benito canyon system. When a canyon loses flow access, usually due to piracy, it is abandoned and eventually filled. During canyon abandonment, fluid escape causes the successive formation of 'cross-canyon ridges' and pockmark trains along buried canyon axes.Based on comparison of canyons in the study area, we recognize two main types of submarine canyons: 'Type I' canyons indent the shelf edge and are linked to areas of high coarse-grained sediment supply, generating erosive canyon morphologies, sandrich fill, and large downslope submarine fans/aprons. 'Type II' canyons do not indent the shelf edge and exhibit smooth, aggradational morphologies, mud-rich fill, and a lack of downslope fans/aprons. Type I canyons are dominated by erosive, sandy turbidity currents and mass wasting, whereas hemipelagic deposition and dilute, sluggish turbidity currents are the main depositional processes sculpting Type II canyons. This morphology-based classification scheme can be used to help predict depositional processes, grain size distributions, and petroleum prospectivity of any submarine canyon.

show abstract

Section: Canyon-pockmark Associationmentioning

confidence: 99%

Two fundamentally different types of submarine canyons along the continental margin of Equatorial Guinea

Jobe

Lowe

Uchytil

2011

Marine and Petroleum Geology

165

View full text Add to dashboard Cite

show abstract

“…by seeping hydrocarbons, especially methane, which can be of biogenic (Vaular et 39 al., 2010) or thermogenic origin (Gay et al, 2006;Solheim and Elverhøi, 1985). 40…”

Section: But Many Published Examples Indicate Formation 38mentioning

confidence: 99%

Characterization of microbial activity in pockmark fields of the SW-Barents Sea

et al. 2012

View full text Add to dashboard Cite

15 16Multibeam bathymetry revealed the occurrence of numerous craterlike depressions, 17 so-called pockmarks, on the sea floor of the Hammerfest Basin and the Loppa High, 18 south-western Barents Sea. To investigate whether these pockmarks are related to 19 ongoing gas seepage, microbial processes associated with methane metabolism 20 were analyzed using geochemical, biogeochemical and microbiological techniques. 21Gravity cores were collected along transects crossing individual pockmarks, allowing 22 a direct comparison between different locations inside (assumed activity center), on 23 the rim, and outside of a pockmark (reference sites). Concentrations of hydrocarbons 24 in the sediment, particularly methane, were measured as headspace (free) gas, and 25 in the occluded and adsorbed gas fraction. Down to a depth of 2.6 m below sea floor 26 2 (mbsf) sulfate reduction rates were quantified by radiotracer incubations. 27Concentrations of dissolved sulfate in the porewater were determined as well. Neither 28 the sulfate profiles nor the gas measurements show any evidence of microbial activity 29 or active fluid venting. Methane concentrations and sulfate reduction rates were 30 extremely low or even below the detection limit. The results show that the observed 31 sediment structures are most likely paleo-pockmarks, their formation probably 32 occurred during the last deglaciation. 33 34 Introduction 35Pockmarks are craterlike depressions in the seabed that form due to expulsion of 36

show abstract

“…If a reservoir rock is not totally sealed, the upward migrating oil (and associated gas) produces chimneys or pockmarks that can be clearly observed on seismic profiles (Tingdahl et al, 2001;Gay et al, 2006). Due to the slight impedance contrast between oil bearing and water bearing sediments (oil-water contact), a phase displacement at the transition from weak to strong reflections occurs.…”

Section: Originmentioning

confidence: 99%

Did massive glacial dewatering modify sedimentary structures on the Amundsen Sea Embayment shelf, West Antarctica?

Weigelt

Uenzelmann-Neben

Gohl

et al. 2012

Global and Planetary Change

View full text Add to dashboard Cite

Multichannel seismic reflection lines collected in the western Amundsen Sea Embayment (ASE) provide an insight into the sedimentary cover on the shelf, which documents glacial processes. Numerous columnar, reflection-poor structures penetrating the sedimentary sequences on the middle shelf form the focus of this study. The features range between 50 and 500 m in width, and from a few metres up to 500 m in height. The columns originate and end at different depths, but do not seem to penetrate to the seafloor. They show well-defined vertical boundaries, and reflection signals can be identified below them. Hence, we exclude gasbearing chimneys. Based on the general seismic reflection characteristics we suggest that the columns originate from dewatering processes which occur close to glaciated areas where fluids are pressed out of rapidly loaded sediments. Likely several mud-diapirs rise from water-rich mud layers within a mixed sedimentary succession and penetrate overlying denser and coarse-grained sediment strata. The presence of fluidescape veins indicates a glacial origin and overprinting of the older sedimentary sequences on the ASE. The locations of the structures indicate that grounded ice sheets reached at least onto the middle shelf during former glacial periods.

show abstract

Evidences of early to late fluid migration from an upper Miocene turbiditic channel revealed by 3D seismic coupled to geochemical sampling within seafloor pockmarks, Lower Congo Basin

Cited by 77 publications

References 54 publications

Two fundamentally different types of submarine canyons along the continental margin of Equatorial Guinea

Two fundamentally different types of submarine canyons along the continental margin of Equatorial Guinea

Characterization of microbial activity in pockmark fields of the SW-Barents Sea

Did massive glacial dewatering modify sedimentary structures on the Amundsen Sea Embayment shelf, West Antarctica?

Contact Info

Product

Resources

About