Quantitative analysis of variations in depositional sequence thickness from submarine channel levees

Skene, Kenneth I.; Piper, David J. W.; Hill, Paul S.

doi:10.1046/j.1365-3091.2002.00506.x

Cited by 88 publications

(115 citation statements)

References 34 publications

Supporting

Mentioning

107

Contrasting

Order By: Relevance

“…Nevertheless, the high accumulation rates in the hemipelagic facies, two to three times higher than those expected accordingly to the distance from the coast (Dennielou, 2003;Jansen et al, 1984), demonstrate a strong depositional influence of the Congo River, either from the surface river plume, or from the canyon. Our dating confirms the strong control of the channel-levee morphology on the turbidite overflow processes, in agreement with the model of channel-levee development proposed by Skene et al, (2002) and the activity of the Congo deep-sea fan during the present sea level high. During the last century, 210 Pb excess data show that more than one meter of turbidite sequences was deposited on the distal levee and on the channel-mouth lobe area, while the accumulation estimated by the radiocarbon dating was much lower for the Late Holocene.…”

supporting

confidence: 90%

“…These features are interpreted as major variations in overflow processes, related to the volume of turbidity currents, and we suggest that the channel depths at which they occur, between ~135 m and ~95 m, represent the average thickness of the turbidity currents flowing down the channel. This transitional area along channel-levee systems is known for other submarine channel-levee (Skene et al, 2002). Upstream, at higher channel depths, turbidity current overflows are rare and/or diluted.…”

mentioning

confidence: 89%

See 1 more Smart Citation

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

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...

show abstract

supporting

confidence: 90%

mentioning

confidence: 89%

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

show abstract

“…External levees can be tens to hundreds of metres high and hundreds to thousands of metres M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 8 wide (Normark and Piper, 1991;Skene et al, 2002;Deptuck et al, 2003;Posamentier, 2003).…”

Section: A N U S C R I P Tmentioning

confidence: 99%

Genesis and character of thin-bedded turbidites associated with submarine channels

Hansen

Callow

Kane

et al. 2015

Marine and Petroleum Geology

117

129

View full text Add to dashboard Cite

Submarine channel related thin-bedded turbidites are deposited in environments such as external levees, internal levees, depositional terraces and at times of channel abandonment.Thin-bedded turbidites are defined as beds that are less than 10cm thick, but the described environments can at times contain beds up to 50cm thick which would be classified as medium or thick-bedded (Boggs, 2006). This paper addresses many examples of these environments from the modern seafloor, outcrop and the subsurface to suggest criteria that assist in the differentiation of levees and terraces from an architectural, sedimentological, M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 2 ichnological and hydrocarbon reservoir perspective. External levees confine channel belts and are elongate sedimentary deposits that are a product of over-spill of turbidity currents from the channel belt they confine. External levees often have predictable vertical, lateral and downstream changes but can commonly be modified by collapse of the inner external levee into the channel, collapse on the outer external levee, sediment waves, and interaction of external levees with topographic features such as other channels, other external levees, basin margins or previous slump/slide blocks, which can greatly modify the sand distribution within them.A combination of internal levees, depositional terraces and slide blocks of external levee sediment make up thin-bedded turbidites within channel belts. We differentiate between wedge shaped internal levees and topographically flat or subdued depositional terraces whose differing geometries and sand distribution reflect the fact that the flow processes involved in the formation of these deposits are different. The characteristic wedge shape of an internal levee requires sufficient space within the channel belt for the over-spilling current to decelerate and deposit the majority of its suspended sediment before reaching the bounding topography of the channel belt. In the case of depositional terraces the space available in the channel belt is insufficient for the current to deposit the majority of its sediment before reaching the bounding topography of the channel belt, creating confined sheet-like deposits.External levees, internal levees and depositional terraces have distinct sedimentological characteristics such as sand bed thickness trends and sedimentary structures that can be used to distinguish them. Together with sedimentological characteristics, in some systems these thin-bedded turbidite deposits contain distinctive trace fossil assemblages, where channel proximal deposits such as proximal external levees, internal levees and depositional terraces M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 3 can have much higher biodiversity than sand-rich channel axes and more mud-dominated outer external levees.The depositional sites for internal levees and depositional terraces within channel belts can be formed by various processes such as entrenchment, point bar accretion, meander bend cutoff, ...

show abstract

“…Our knowledge of their flow behaviour is generally indirect, for example, based on the grain size distribution of sediments deposited from the flows [347][348][349], geometry of channel levées [350] or channel deposits [267]. The average velocities of some turbidity current fronts are known from the timing of successive breaks of telephone cables [351].…”

Section: (Ii) Turbidity Currents and Other Sedimentary Flowsmentioning

confidence: 99%

Aspects of marine geoscience: a review and thoughts on potential for observing active processes and progress through collaboration between the ocean sciences

Mitchell

2012

Phil. Trans. R. Soc. A.

View full text Add to dashboard Cite

Much progress has been made in the UK in characterizing the internal structures of major physiographic features in the oceans and in developing understanding of the geological processes that have created or shaped them. UK researchers have authored articles of high impact in all areas described here. In contrast to terrestrial geoscience, however, there have been few instrumented observations made of active processes by UK scientists. This is an area that could be developed over the next decades in the UK. Research on active processes has the potential ability to engage the wider public: Some active processes present significant geo-hazards to populations and offshore infrastructure that require monitoring and there could be commercial applications of technological developments needed for science. Some of the suggestions could involve studies in shallow coastal waters where ship costs are much reduced, addressing tighter funding constraints over the near term. The possibilities of measuring aspects of volcanic eruptions, flowing lava, turbidity currents and mass movements (landslides) are discussed. A further area of potential development is in greater collaboration between the ocean sciences. For example, it is well known in terrestrial geomorphology that biological agents are important in modulating erosion and the transport of sediments, ultimately affecting the shape of the Earth's surface in various ways. The analogous effect of biology on large-scale geomorphology in the oceans is also known but remains poorly quantified. Physical oceanographic models are becoming increasingly accurate and could be used to study further the patterns of erosion, particle transport and deposition in the oceans. Marine geological and geophysical data could in turn be useful for further verification of such models. Adapting them to conditions of past oceans could address the shorter-period movements, such as due to internal waves and tides, which have been barely addressed in palaeoceanography.

show abstract

Quantitative analysis of variations in depositional sequence thickness from submarine channel levees

Cited by 88 publications

References 34 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

Genesis and character of thin-bedded turbidites associated with submarine channels

Aspects of marine geoscience: a review and thoughts on potential for observing active processes and progress through collaboration between the ocean sciences

Contact Info

Product

Resources

About