Distributary channel meandering and bifurcation patterns on the Amazon deep-sea fan as revealed by long-range side-scan sonar (GLORIA)

Damuth, John E.; Kolla, V.; Flood, Roger D.; Kowsmann, Renato Oscar; Monteiro, Marcelo Costa; Gorini, Marcus Aguiar; Palma, Jorge J. C.; Belderson, R. H.

doi:10.1130/0091-7613(1983)11<94:dcmabp>2.0.co;2

Cited by 152 publications

(83 citation statements)

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“…Previous studies (Damuth, et al, 1983a(Damuth, et al, , 1988Manley and Flood, 1988;Flood et al, 1991) suggest that only one channel levee system is active at any given time and abandonment of an active channel by avulsion leads to the formation of a new channel levee nearby. Therefore, channellevee systems grow both vertically and downfan (Fig.…”

Section: Channel Leveesmentioning

confidence: 99%

“…2, 3). Because the spatial distribution of these units is very well constrained on the Amazon Fan (Damuth et al, 1983a(Damuth et al, , 1983bDamuth et al, 1988;Manley and Flood, 1988;Flood et al, 1991;Pirmez, 1994;Pirmez and Flood, 1995;, average grain-size profiles for each acoustic unit, both downfan and crossfan, can be constructed from the drilled sites.…”

Section: Comparison With Acoustic Unitsmentioning

confidence: 99%

“…The channel axes are associated with high-amplitude reflections (HARs, Kastens and Shor, 1985) on seismic reflection profiles. The relative age relationships of the systems were determined for the surficial channels by overlapping stratigraphic relationships (named 1 through 6C; Damuth et al, 1983aDamuth et al, , 1983bDamuth et al, , 1988Damuth and Flood, 1984), whereas the stratigraphy of buried channel-levee systems used overlapping stratigraphic relationships as well as depth to levee crests (given color names; Manley and Flood, 1988) (Table 1; Figs. 1, 2).…”

Section: Introductionmentioning

confidence: 99%

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Grain-size characterization of Amazon Fan deposits and comparison to seismic facies units

Manley¹,

Pirmez²,

Busch³

et al. 1997

Proceedings of the Ocean Drilling Program, 155 Scientific Results

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Prior to Ocean Drilling Program Leg 155, the architecture of the Amazon Fan, as well as those of other modern submarine fans, had been investigated primarily by seismic reflection profiles. The acoustic facies and stratal patterns observed on these profiles provided a wealth of information that allowed deciphering fan growth patterns and the geometry of fan deposits. However, lithofacies could only be inferred from the seismic reflection data. Here we analyze grain-size data from 13 sites drilled during Leg 155, and place the results in the context of the stratigraphic units interpreted from seismic reflection data. Clay, silt, and fine sand are the dominant grain sizes of all cores retrieved from the Amazon Fan. In this mud-rich fan, sand is concentrated within the channel thalweg, at the base of channel-levee systems within the middle fan, and forms a significant fraction of the lower fan deposits drilled. All channel-levee deposits drilled are characterized by a fining-upward trend and by an overall coarsening in the downfan direction. Downfan coarsening of the levee deposits probably results from very efficient sorting associated with the channelized flow of turbidity currents together with the overall decrease in channel relief downfan. Finingupward cycles within a channel-levee system are observed in the middle fan where multiple phases of levee development are stacked upon each other. Each growth phase is marked by an abrupt coarsening that marks a channel bifurcation occurring downslope, followed by a fining-upward sequence of levee aggradation. Channel bifurcation results in the reworking of older channel deposits, and the formation of laterally widespread units. High-amplitude reflections (HARs) beneath the channel axis and high-amplitude reflection packet (HARPs) units are composed of two distinct grain-size populations. HARs and HARPs are the coarsest units that form the fan, with sizes up to 0 ø. Both units display an overall coarsening downfan. These characteristics are likely the result of multistep transport of sand downfan. Thick acoustically transparent units on seismic profiles are correlated to large mass-transport deposits, displaying grain-size characteristics similar to levee deposits with an overall finingupward and downfan-coarsening trend.

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Section: Channel Leveesmentioning

confidence: 99%

Section: Comparison With Acoustic Unitsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Grain-size characterization of Amazon Fan deposits and comparison to seismic facies units

Manley¹,

Pirmez²,

Busch³

et al. 1997

Proceedings of the Ocean Drilling Program, 155 Scientific Results

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“…Laterally away from the channel axis, the overbank deposits of an individual channel can be traced with seismic reflection data for 10-20 km, but sediment carried by individual turbidity currents that spilled from the channel probably extends even farther, contributing to conformable "hemipelagic" deposits covering much of the fan; these can only be detected with cores and very high-resolution seismic techniques Pirmez, 1994). Damuth et al (1983aDamuth et al ( , 1983bDamuth et al ( , 1988 and Manley and Flood (1988) showed that the distributary channel network on the surface and in the subsurface of the Amazon Fan developed as a result of repeated channel bifurcations. Because individual channel-levee systems onlap one another (Fig.…”

Section: Introductionmentioning

confidence: 99%

Sandy turbidite successions at the base of channel-levee systems of the Amazon Fan revealed by FMS logs and cores: unraveling the facies architecture of large submarine fans

Pirmez¹,

Hiscott²,

Kronen³

1997

Proceedings of the Ocean Drilling Program

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Continuous bed-by-bed descriptions of thick, sand-rich turbidite successions drilled at five sites on the Amazon Fan have been prepared using a combination of Formation MicroScanner (FMS) and geophysical wireline logs. FMS images enable a complete lithologic section to be derived at Sites 931, 935, 936, 944, and 946 over intervals of poor core recovery up to several tens of meters thick, characterized as high-amplitude reflection packets (HARPs) in the seismic data. On the middle fan, HARP deposition coincides in time with the initiation of a new channel segment after channel bifurcation. Toward the lower fan, HARP units tend to stack directly on top of each other, as overbank deposits thin downfan; these HARP units probably contain deposits formed at the mouths of channels.The turbidite successions within the HARP intervals include sand bodies 5-25 m thick formed of sand beds 0.1-4 m thick. These sand bodies correlate with episodes of channel bifurcation on the middle fan. Most beds thicker than ~1 m contain mud clasts, interpreted to result from upslope levee erosion and channel entrenchment after channel bifurcation. On the lower fan, bed clusters and sets of amalgamated beds form sand bodies as thick as 50 m, with individual beds often exceeding 3 m in thickness and containing abundant mud clasts. Most bed clusters show no apparent trends in bed thickness, although a few clusters show clear thickening-upward trends interpreted to represent channel mouth progradation.Other studies suggest that, for turbidites, the number of beds whose thickness is greater than T is proportional to T -B , where B is a positive exponent. The scaling exponent required to fit the Amazon Fan bed-thickness distributions is different for beds thinner and thicker than about 0.35 m. This difference is attributed to either selective removal, by erosion, of beds thinner thañ 0.35 m, or greater confinement, by seafloor morphology, of flows that deposited such thin beds on the fan surface. The flows that deposited beds thicker than 0.35 m in HARP units were apparently able to freely spread in the interlevee area.The so-called mud-rich Amazon Fan contains thick sheet-like units indistinguishable in facies and sand content from many ancient mud/sand-rich successions described by field geologists. Although it remains true that small fans at convergent and strike-slip plate boundaries are potentially good analogs for such ancient deposits, larger channel-levee-dominated systems that periodically supply sand to interchannel depressions following avulsions also need to be considered.

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“…Detailed mapping of the Amazon Fan with seismic-reflection profiles, long-range side-scan sonar (GLORIA), and SeaBeam bathymetry have shown the development of the extensive MTDs of more than 50,000 km 3 (Damuth et al, 1983;Damuth and Flood, 1985;Flood and Damuth, 1987;Manley and Flood, 1988;Damuth et al, 1988;Flood et al, 1991) (Figs. 1, 2).…”

Section: Introductionmentioning

confidence: 99%

Computed tomography scan analysis of Site 941 cores, western mass-transport deposit, Amazon Fan

Soh¹

1997

Proceedings of the Ocean Drilling Program, 155 Scientific Results

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X-ray computed tomography (CT) and pore-water chemistry analyses were performed using whole round-core samples from the regionally extensive Western Mass-Transport Deposit (WMTD), Site 941 of Ocean Drilling Program (ODP) Leg 155, on the Amazon Fan. Here, the CT value has a good correlation with the bulk density and water content of the sediment. The CT image shows a plume-shaped, fluidized structure with gas bubbles in the mud sediment, Sample 155-941B-6H-4, 0−20 cm, at 47 meters below seafloor, at the top of a 2-m-thick soupy and gassy sediment interval. Significant increase in the water content was recognized in the fluidized sediment when compared to those of the surrounding unfluidized sediments. The content coincided with the fresh-water dilution estimated from the anomalous pore-water chemistry. The fluidization was thus caused by the dissociation of gas hydrate. The quantitative CT value analysis allows us to estimate that the percentage of gas hydrate content reaches ~10 vol% of the fluidized sediment (17.5 vol% of the pore space). This content seems to be equivalent to the highest contents of the gas hydrate above bottom-simulating reflectors (BSRs) reported from other hydrate regions. BSRs underlie parts of the continental slope updip from the WMTD. The 2-m-thick soupy and gassy sediment is inferred to be derived from a part of "missing" sediment interpreted from seismic-reflection profiles of the source area of the WMTD that is bounded by scarps up to 200 m high. Furthermore, the disassociation of gas hydrate should be the most important trigger mechanism for causing the regionally extensive slope failure that produced the WMTD.

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Distributary channel meandering and bifurcation patterns on the Amazon deep-sea fan as revealed by long-range side-scan sonar (GLORIA)

Cited by 152 publications

References 0 publications

Grain-size characterization of Amazon Fan deposits and comparison to seismic facies units

Grain-size characterization of Amazon Fan deposits and comparison to seismic facies units

Sandy turbidite successions at the base of channel-levee systems of the Amazon Fan revealed by FMS logs and cores: unraveling the facies architecture of large submarine fans

Computed tomography scan analysis of Site 941 cores, western mass-transport deposit, Amazon Fan

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