Fine-grained turbidites of the Amazon Fan: facies characterization and interpretation

Piper, David J. W.; Deptuck, Mark E.

doi:10.2973/odp.proc.sr.155.208.1997

Cited by 55 publications

(48 citation statements)

References 11 publications

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“…In core KZAI14, the number of turbidites compared to the historical timescale suggests that the frequency of overbank deposition was constant over the last 5000 years, with about one overbank deposit every 45-55 years. This is lower than the frequency estimated for the Amazon fan, with about one overbank deposit every 3-8 years during low-stand periods (Piper and Deptuck 1997), but low-stand activity of the Congo system is not recorded in the cores. This frequency is also low in comparison with the frequency of cable breaks, i.e.…”

Section: Sedimentation Along the Present Channel-levee And Lobementioning

confidence: 50%

Geological overview of the Angola–Congo margin, the Congo deep-sea fan and its submarine valleys

Savoye

Babonneau

Dennielou

et al. 2009

Deep Sea Research Part II: Topical Studies in Oceanography

132

155

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The Congo deep-sea fan is one of the largest fans in the world still affected by presently active turbidity currents. The present activity of deep-sea sedimentary processes is linked to the existence of a direct connection between the Congo River estuary and the Congo canyon head that allows relatively continuous sediment feeding of the deep-sea environment, in spite of a wide continental shelf (150 km). Because of this important activity in terms of sedimentary processes, the deep-sea environment of the Congo-Angola margin presents major interests concerning physical, chemical and biological studies near the sea floor. The main aim of this paper is to present the initial geological context of the BioZaire Program, showing a synthesis of the major results of the ZaïAngo Project including (1) the brief geological setting of the Congo-Angola margin, (2) the structure of the modern Congo deep-sea fan, (3) the sedimentary architecture of the recent Congo turbidite system (from the canyon to the distal lobes), and (4) the recent and present turbidite sedimentation. In order to provide useful information and advice relevant to biological and geochemical studies across the Congo sedimentary system, this article focuses on the present sedimentary processes and the present activity of turbidity current along the Congo canyon and channel.Keywords : Congo-Angola margin, Congo channel, sedimentary deposits, turbidite .1 IntroductionThe accumulation of marine sediment seaward of the Congo River estuary is probably one of the greatest in the world for a submarine system that is still active today. In the continental domain, the Congo sedimentary system is composed by a wide drainage basin, the river and its tributaries. In the nearshore and marine domain: it consists of the estuary, the canyon, which acts mainly as a by-pass zone, and finally an area of preferential sedimentation at the foot of the continental slope and in the deep basin. The Congo submarine system has been geologically studied since Buchanan in 1887 (submarine cable survey) and was the focus of the ZaïAngo project team from 1998 to 2005. Several types of evidence of Holocene and very recent activity in the canyon have been described and linked to sedimentary processes such as turbidity currents, river floods, slides, gas hydrate formation and fluid escape. The aim of this paper is to synthesize the geological knowledge of the area and in particular the results of the ZaïAngo project in order to provide useful information and advice relevant to biological and geochemical studies across the Congo sedimentary system. Marine biologists and oceanographers are usually not familiar with turbidite deposits. These sedimentary deposits were first recognised and described in outcrops of ancient sedimentary series (Bouma, 1962;Walker, 1978;Mutti, 1992). They are generated by submarine gravity processes and they build large sedimentary systems in deep-water environments, termed deep-sea fans. Deep-sea fans are well developed from the foot of the continental slope...

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Section: Sedimentation Along the Present Channel-levee And Lobementioning

confidence: 50%

Geological overview of the Angola–Congo margin, the Congo deep-sea fan and its submarine valleys

Savoye

Babonneau

Dennielou

et al. 2009

Deep Sea Research Part II: Topical Studies in Oceanography

132

155

View full text Add to dashboard Cite

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“…16). Using an annual event periodicity, which may be more likely for systems like Amazon Fan (Piper and Deptuck, 1997;Pirmez and Imran, 2003), allows for even less sediment to accumulate in the source area and makes the outburst flood event even more dramatically unique (several orders of magnitude greater volume, Fig. 16).…”

Section: Pliocene-quaternary Evolution Of Laurentian Fanmentioning

confidence: 98%

Late Cenozoic evolution of Laurentian Fan: Development of a glacially-fed submarine fan

Skene

Piper

2006

Marine Geology

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“…For instance, in the Amazon fan, Hiscott et al (1995) and Piper and Deptuck (1995), clearly state that the composition of the sediment overspill and associated hydrodynamic processes is controlled by the height of a turbidite current and the channel depth, and that the grain size of overspilled sediments is negatively correlated to the channel depth. Also, the fining upward trend of the grain size in the levee deposits is interpreted as the imprint of the increase of the channel relief through time related to the levee growth (Manley et al, 1997).…”

Section: Introductionmentioning

confidence: 98%

Vertical grain-size variability within a turbidite levee: Autocyclicity or allocyclicity? A case study from the Rhône neofan, Gulf of Lions, Western Mediterranean

et al. 2006

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The fining upward trend commonly described on levees of turbidite systems can be either attributed to changes in the sediment supply (external forcing = allocyclic) or changes in the spillover processes related to the growth of the levee (internal forcing = autocyclic). However the real causes remain speculative and difficult to demonstrate. Knowledge of vertical change in flow velocity (or grain size) in turbidity currents, of the turbidity current's height, as well as the growth rate of a levee are theoretically sufficient to describe the evolution of the grain size of a leveed turbidite sequence deposited by spillover processes.A piston core (MD99-2344) retrieved on the right levee of the Petit-Rhône neofan, sampled an 8.50 m long turbidite sequence containing more than one hundred turbidite beds and showing a marked fining upward trend. With the help of two profiles describing respectively the vertical velocity [Stacey, M. and Bowen, A.J., 1988b. The vertical structure of turbidity currents and a necessary condition for self-maintenance, Journal of Geophysical Research, pp. 3543-3553.] and the vertical grain size [Migeon, S., 2000. Dunes géantes et levées sédimentaires en domaine marin profond: approche morphologique, sismique et sédimentologique. PhD Thesis, Université Bordeaux 1, Talence, France, 288 pp.] of a turbidity current, and a simple graphical method, we test several hypotheses on the height of the turbidity current and on the grain size at the bottom of the turbidity current and we attempt to reproduce the vertical fining upward trend.Our results show that the fining upward trend of the turbidite facies can be explained by the aggradation of the turbidite levee and the gradual confinement of the turbidity currents in the channel. This is, therefore, an autocyclical phenomenon. However a high frequency variability of the grain size overprinted on the trend cannot be explained by internal forcing and is believed to be allocyclical, depending on changes to the sediment input. The vertical grain-size profile allows more realistic flow conditions to be determined and shows that the vertical velocity profile does not describe the ability of turbidity current to transport sediment. This simple graphical method allows a better understanding and quantification of the forcing on turbidite deposits and improves description of the characteristics of the turbidity currents from the grain size of the deposits.

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Fine-grained turbidites of the Amazon Fan: facies characterization and interpretation

Cited by 55 publications

References 11 publications

Geological overview of the Angola–Congo margin, the Congo deep-sea fan and its submarine valleys

Geological overview of the Angola–Congo margin, the Congo deep-sea fan and its submarine valleys

Late Cenozoic evolution of Laurentian Fan: Development of a glacially-fed submarine fan

Vertical grain-size variability within a turbidite levee: Autocyclicity or allocyclicity? A case study from the Rhône neofan, Gulf of Lions, Western Mediterranean

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