Echo character of the western equatorial Atlantic floor and its relationship to the dispersal and distribution of terrigenous sediments

Damuth, John E.

doi:10.1016/0025-3227(75)90047-x

Cited by 231 publications

(150 citation statements)

References 7 publications

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“…Such waves, however, are not diagnostic of contourites as they can also be formed by turbidity currents. For instance, they have been observed on the backside of levées bounding deep-sea fan channels (Hamilton, 1967;Damuth, 1975;Hess and Normark, 1976;Normark et al, 1980). In these cases, however, a contour-current origin cannot entirely be ruled out.…”

Section: Interpretation Of Seismic Sequencesmentioning

confidence: 99%

Late Neogene and Quaternary sedimentation on the continental slope and upper rise offshore southeast Greenland: interplay of contour and turbidity processes

Clausen¹

1998

Proceedings of the Ocean Drilling Program

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Three seismic sequences have been identified within the late Neogene and Quaternary deep-sea sedimentary succession on the continental slope and rise in the Irminger Basin offshore southeast Greenland. They are bounded at the base by unconformities of middle Pliocene, early Pliocene, and (?) late Miocene ages, respectively. The sequences form large, elongate drifts on the seafloor, oriented almost perpendicular to the continental rise. The seismic facies of the two youngest sequences suggest mixed deposition both from contour and turbidity currents off the then glaciated shelf. Inter-drift channel-levée complexes recognized within the youngest sequence (middle Pliocene-Pleistocene) were deposited from turbidity currents. The major turbidity channels, originating at the base of the continental slope, are prolongations of transverse shelf trough/trough-mouth fan systems. A moat zone separates the elongate drifts from the continental slope. The depth stratum of the modern southward-flowing deepsea contour-currents correlates with the position of this moat zone. It is concluded that the Labrador Sea Water Current has played a far more important role in sculpturing the continental slope and rise than earlier recognized. Mixed depositional systems as described in this paper might prove to be a widespread feature at high-latitude glaciated margins.

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Section: Interpretation Of Seismic Sequencesmentioning

confidence: 99%

Late Neogene and Quaternary sedimentation on the continental slope and upper rise offshore southeast Greenland: interplay of contour and turbidity processes

Clausen¹

1998

Proceedings of the Ocean Drilling Program

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“…Hollister & Heezen, 1972;Damuth, 1975;Embley, 1976;Flood, 1980;Jacobi & Hayes, 1992;Baptista Neto et al, 1996;Reddy & Rao, 1997;Dowdeswell et al, 1997;Zaragosi et al, 2000;Hong & Chen, 2000;Quaresma et al, 2000;Lee et al, 2002). The types and distribution of the echo-character can be used as basis for the interpretation of depositional and erosional processes, since the echo types are mainly controlled by surface topography, subsurface geometry and sedimentary texture of the superficial and sub-superficial sediments and rocks (Damuth, 1975(Damuth, , 1980Embley, 1976;Damuth & Hayes, 1977).…”

Section: Introductionmentioning

confidence: 99%

Distinctive sedimentary processes in Guanabara Bay - SE/Brazil, based on the analysis of echo-character (7.0 kHz)

Catanzaro¹,

Neto²,

Guimarães³

et al. 2004

Rev. Bras. Geof.

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ABSTRACT. Guanabara Bay bottom sediments and seabed characteristics were analysed using high-resolution (7 kHz) sub-bottom profiles associated with particle size analyses of 92 bottom sediment samples. Eight types of echo-characters were identified revealing the strong relation with the particle size distribution. Sandy bottom areas presented strong echo reflections, without sub-bottom penetration (Echo types I and III), while in muddy areas sub-bottom reflections showed the acoustic basement delineating buried sugar-loaf hills and infilled-valley features (Echo type IV). The presence of shallow gas within the sediments is indicated by acoustic blanket and a series of bottom-multiple reflections (Echo types Va and Vb). Erosion by bottom currents and artificial mechanical dredging are suggested by truncations of sub-bottom reflections and a wrinkled seabed surface (Echo types VI and VII). Crystalline basement outcrops on the seabed are recognized by multiple or single hyperbolae with varying elevations above the bay bottom (Echo type II).

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“…Whereas the acoustical response from the seabed is primarily a function of sediment type, physical properties, and morphology (e.g., Smith & Li 1966;Damuth 1978Damuth , 1980Pratson & Laine 1989), it may also be influenced by variables unrelated to the seabed (e.g., King 1965;Damuth 1975) including: (1) instrument settings, particularly overall gain and time variable gain adjustments; (2) pitch and roll of the survey vessel; and (3) orientation of survey lines relative to linear morphologic elements. The effects of these variables on the data have been minimised by relying mainly on 3.5 kHz records collected during NZOI cruise 1139, when the bulk of the survey was performed in fairly uniform sea conditions using consistent instrument settings.…”

Section: Methodsmentioning

confidence: 99%

“…However, a more realistic appreciation of Cook Strait sedimentation may be obtained by combining available sediment data with 3.5 kHz, high-resolution, seismic profiles. Such profiles significantly enhance our interpretation of more traditional sediment charts in that: (1) seismic reflection is in part a function of sediment lithology and enables a more accurate mapping of substrates (e.g., Smith & Li 1966;Embley & Langseth 1977;Damuth 1980); (2) profiles record morphological data that assist with the identification of sedimentary processes (e.g., currentinduced bedforms; sediment body geometry); and (3) seismic sections add a stratigraphic perspective to interpretation.…”

Section: Introductionmentioning

confidence: 99%

Acoustical characterisation of seafloor sediments and its relationship to active sedimentary processes in Cook Strait, New Zealand

Carter¹

1992

New Zealand Journal of Geology and Geophysics

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3.5 kHz seismic profiles are used to characterise the seabed in Cook Strait. The various acoustical responses have been classified into nine groups or echo-types which, together with sediment samples, photographs, and side-scan sonography, provide an insight into modern erosional and depositional.processes operating in the strait.Much of northern Cook Strait is underlain by semiconsolidated, late Pleistocene sediments that are eroded by strong, tide-dominated currents even at depths >200 m. Locally, erosion of these deposits is impeded by a lag gravel pavement that occupies much of the 150-350 m deep central strait. The same strong currents effectively transport bedload along the Wellington continental shelf, which is a rocky platform with a patchy veneer of mobile sand and gravel. Outside the main tidal stream, within semiprotected embayments, deposition is manifest by prominent sediment bodies of mud and sand prograding across the inner-middle shelf. Seaward of the shelf, in southern Cook Strait, the seafloor is dissected by a complex of submarine canyons that appear to syphon off tidally transported sand to the nearby Hikurangi Trough. However, in at least one place, transport is impeded by a slide blocking the canyon axis. Outside submarine canyons, products of gravitational mass movement are not conspicuous, even though Cook Strait lies across a zone of high seismicity. This scarcity of evidence is, in part, attributed to current modification of any such deposits.

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Echo character of the western equatorial Atlantic floor and its relationship to the dispersal and distribution of terrigenous sediments

Cited by 231 publications

References 7 publications

Late Neogene and Quaternary sedimentation on the continental slope and upper rise offshore southeast Greenland: interplay of contour and turbidity processes

Late Neogene and Quaternary sedimentation on the continental slope and upper rise offshore southeast Greenland: interplay of contour and turbidity processes

Distinctive sedimentary processes in Guanabara Bay - SE/Brazil, based on the analysis of echo-character (7.0 kHz)

Acoustical characterisation of seafloor sediments and its relationship to active sedimentary processes in Cook Strait, New Zealand

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