Northwest African Continental Rise: Effects of Near-Bottom Processes Inferred from High-Resolution Seismic Data

Jacobi, Robert D.; Hayes, Dennis E.

doi:10.1007/978-1-4684-6500-6_12

Cited by 27 publications

(26 citation statements)

References 54 publications

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“…Cita et al (1984a) (Kenyon et al 1975;Stride et al 1977). The 3.5 kHz analysis is after criteria of Jacobi & Hayes (1993). Acoustic facies A-C are explained in the text; profiles shown in Fig.…”

Section: Geological Setting and Previous Workmentioning

confidence: 99%

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Turbidite flux, architecture and chemostratigraphy of the Herodotus Basin, Levantine Sea, SE Mediterranean

Reeder

Rothwell

Stow

et al. 1998

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The Herodotus Basin is the deepest part of the SE Mediterranean and receives allochthonous sediments as turbidity currents and debris flows from around its margin. During the late Quaternary, characteristic supply has been from at least four sources. These are (1) dark coloured, calcium carbonate-poor fine-grained turbidites derived from the Nile Cone to the south and south-east, (2) lighter coloured, calcium carbonate-rich, slightly coarser-grained turbidites derived from the Libyan-Egyptian shelf to the south, (3) small, light brown foraminifer-rich, muddy-silty turbidites derived from the Cyprus-Eratosthenes seamount (Anatolian Rise) carbonate shelf to the east, and (4) small localized debris flow deposits derived from the Mediterranean Ridge to the north. During the late Quaternary (0-60 ka), and specifically the period of 0-27 ka, the basin has filled predominantly with allochthonous material derived from the Nile Cone, although one megaturbidite of basinwide extent was derived from the Libyan-Egyptian shelf. Turbidites have been correlated across the Herodotus Basin using the technique of chemostratigraphy. Matching the results of geochemical analysis may show whether or not the beds in different cores were deposited by the same mass-wasting event, for individual turbidites commonly have diagnostic and unique geochemical 'fingerprints' in terms of major, minor and trace element composition. Sediment budgets for the three main turbidite sources are calculated. The cumulative volume of the sedimentary input for the Nile Cone-derived turbidites over the last 27 ka is c. 500 km 3, giving an average sedimentation rate of c. 45 cm ka -1, and a volume per unit time of 18 km 3 ka -1. A megaturbidite, derived from the Libyan-Egyptian shelf, is of basinwide extent and has a volume of c. 400 km 3.

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Section: Geological Setting and Previous Workmentioning

confidence: 99%

“…Echo types on the 3.5 kHz records have been classified on the basis of clarity and continuity of sub-bottom echoes, the depth of sub-sea-floor penetration by the acoustic signal, and microtopography (cf. Kidd et al 1985;Jacobi & Hayes 1993). Three acoustic facies or province types have been identified, named A-C.…”

Section: Morphology and Acoustic Faciesmentioning

confidence: 99%

Turbidite flux, architecture and chemostratigraphy of the Herodotus Basin, Levantine Sea, SE Mediterranean

Reeder

Rothwell

Stow

et al. 1998

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“…Upwelling and bottom-water erosion (Arthur et al, 1979;Sarnthein et al, 1982;Tiedemann et al, 1989;Jacobi and Hayes, 1992) and an increase in turbidites, slides, slumps, and submarine canyon erosion (von Rad and Wissmann, 1982;Masson et al, 1992) have also been noted along the continental margin of northwestern Africa. Current erosion may be responsible for some of these masswasting events at Sites 955 and 956.…”

Section: Quaternary (16 To 0 Ma)mentioning

confidence: 99%

“…= miscellaneous turbidites. ceives sediment from both the Canary Islands and the African continent (i.e., Jacobi and Hayes, 1992;Fig. 2).…”

Section: Sedimentationmentioning

confidence: 99%

“…Slumped intervals have slightly different interbedded lithologies than the coherent strata above and below the disrupted sequences, suggesting that the slumped sediment may have moved considerable distances. Intensified North Atlantic Deep Water causing seafloor erosion (Franks et al, 1982), coastal upwelling noted at Site 397 (Sarnthein et al, 1982;Tiedemann et al, 1989;Jacobi and Hayes, 1992), and a Pliocene angular unconformity present on the shelf and upper slope off northwestern African (Von Rad and Wissmann, 1982) may be evidence that current erosion and high biogenic gas concentrations along the continental slope are the cause of these slope failures. Additionally, the hiatus at Site 955 (1.6 to 2.37 Ma) may be related to current erosion.…”

Section: Pliocene (53 To 16 Ma)mentioning

confidence: 99%

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Provenance and sedimentologic variations of turbidite and slump deposits at Sites 955 and 956

Goldstrand¹

1998

Proceedings of the Ocean Drilling Program, 157 Scientific Results

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At two of the seven sites drilled during Leg 157, located south of the Canary Islands (Sites 955 and 956), more than 1000 thinly bedded to finely laminated volcaniclastic and nonvolcaniclastic silt and sand turbidite units interbedded within thick sequences of hemipelagic mud were recovered. The sediments range in age from Pleistocene to middle Miocene. Turbidite deposits composed mostly of volcaniclastic detritus are related to known periods of volcanism in the Canary Islands. The nonvolcaniclastic turbidites include various mixtures of quartz and foraminifer sand and silt derived from the continental margin of northwestern Africa. Shallow marine bioclastic deposits are thicker at Site 956 than at Site 955, suggesting that these sediments were derived from the southern Canary Islands.Although age constraints cannot be precisely defined at these sites, the general trend of sedimentation is consistent with sealevel variations being responsible for transport of the continentally derived turbidites. Quartz-rich turbidite deposits composed of well-rounded, very fine-grained sand were derived from Saharan eolian sands that migrated onto the subaerially exposed continental shelf and were shed into the deep marine environment during falls in sea level. Shallow marine bioclastic and foraminifer-rich turbidites also correspond to periods of sea-level fluctuations. However, the presence of volcaniclastic material within several bioclastic deposits indicates volcanic activity may have been responsible for some of their deposition.Large-scale submarine slumping appears to be more active during periods of intensified bottom currents and upwelling. Additionally, slumping was more frequent at Site 956 on the lower flank of Gran Canaria. Slump block ages are only slightly older than those of the surrounding sediment, and mass movement may have resulted from increased sedimentation and/or earthquakes associated with Canary Islands volcanism.

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Submarine Landslides in an Upwelling System

Urlaub

Krastel

Schwenk

2019

Submarine Landslides

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Northwest African Continental Rise: Effects of Near-Bottom Processes Inferred from High-Resolution Seismic Data

Cited by 27 publications

References 54 publications

Turbidite flux, architecture and chemostratigraphy of the Herodotus Basin, Levantine Sea, SE Mediterranean

Turbidite flux, architecture and chemostratigraphy of the Herodotus Basin, Levantine Sea, SE Mediterranean

Provenance and sedimentologic variations of turbidite and slump deposits at Sites 955 and 956

Submarine Landslides in an Upwelling System

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