Continental shelf geomorphic features off Portuguese Guinea, Guinea, and Sierra Leone (West Africa)

McMaster, Robert L.; Lachance, Thomas P.; Ashraf, Asaf

doi:10.1016/0025-3227(70)90015-0

Cited by 27 publications

(9 citation statements)

References 7 publications

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“…In addition to those in our study area, cobble beds have been reported off Sierra Leone (Longhurst 1958, McMaster et a!. 1970, Cote d'Ivoire (Barbey 1968, Martin 1971, Togo (Barbey 1968), and from the islands of Principe and Sao Tome in the Gulf of Guinea (Carpine 1959) and Ascension in the mid-Atlantic (Price and John 1978).…”

Section: Cobblessupporting

confidence: 64%

“…In addition to those in our study area, cobble beds have been reported off Sierra Leone (Longhurst 1958, McMaster et al 1970), C6te d'Ivoire (Barbey 1968, Martin 1971, Togo (Barbey 1968), and from the islands of Principe and Sao Tome in the Gulf of Guinea (Carpine 1959) and Ascension in the mid-Atlantic (Price and John 1978). Beds of fossil cobbles are mentioned from deep water off the West African coast, and two such cobbles collected at a depth of 100 m off C6te d'Ivoire have been dated around 13 000 yr BP.…”

Section: Introductionsupporting

confidence: 64%

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Ecology of Subtidal Algae on Seasonally Devastated Cobble Substrates off Ghana

Lieberman¹,

John²,

Lieberman³

1979

Ecology

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JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Ecological Society of America is collaborating with JSTOR to digitize, preserve and extend access to Ecology. Abhstra ct. The growth of subtidal algae on calcareous cobbles is restricted to a short (2-4 mo) growing season. Most algae are destroyed during rainy season storms due to surge and cobble tumbling; algal density is low throughout the year. Significant interspecific competition does not occur on cobbles, and no species/area relationship could be demonstrated. The number of species per cobble is correlated with cobble moment of inertia (resistance to tumbling) during the rainy season. Species diversity on cobbles is significantly higher than on neighboring rocky reefs. Available evidence suggests an annual floristic cycle, although biomass and diversity are closely related to short-term weather conditions. Ephemerals, annuals, pseudoannuals, and perennials appear sequentially during the growing season. Species with greater potential size reach peak abundance late in the growing season, although many never reach maximum size or reproduce on cobbles. These longevity and size trends cannot be said to constitute adaptive strategies on cobbles. The high species diversity observed on cobbles is adequately explained by seasonal disturbance.

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Section: Cobblessupporting

confidence: 64%

Section: Introductionsupporting

confidence: 64%

Ecology of Subtidal Algae on Seasonally Devastated Cobble Substrates off Ghana

Lieberman¹,

John²,

Lieberman³

1979

Ecology

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“…Three main zones can be distinguished depending on the sediment's nature and bathymetry. There is a shallow area (20–75 m depth), with soft bottoms (mud and sand) in the northern area (mainly related to the river mouth), and with hard bottoms from Bijagos to the Guinean border in the south, externally associated with coral reefs and crossed by numerous submarine canyons and valleys (McMaster et al , 1971). At bottoms deeper than 200 m, deposits vary from soft (mud and sand) to hard (rubble, gravel and rocks).…”

Section: Methodsmentioning

confidence: 99%

Distribution, abundance and assemblages of decapod crustaceans in waters off Guinea-Bissau (north-west Africa)

et al. 2011

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This study constitutes a first contribution to the knowledge of the ecology of the decapod crustaceans in waters off Guinea-Bissau. Samples were collected during a survey undertaken between October and November 2008. A total of 122 species of decapod crustaceans were identified. Results showed an increase of decapod biomass and abundance with depth, reaching maxima values in the 200–500 m depth stratum but decreasing at depths over 500 m. Average diversity by strata increased with depth, with maximum over the deep slope. Seven main assemblages were identified: five primarily associated with depth—coastal shelf (<60 m), shelf (60–200 m), upper slope (200–300 m), middle slope (300–500 m), deep slope (500–1000 m)—and two other northern shelf assemblages affected by sediment type—coastal shelf-north (<50 m) and shelf-north (50–100 m). Species of each assemblage are typified. This study provides new information about composition, distribution, abundance and assemblage structure of decapod crustaceans in Guinea-Bissau that may be useful for future assessment of the effect of trawling pressure in the area.

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“…The pre‐Holocene sea‐level history of the west African coast is poorly known. Radiocarbon evidence from fossil strand deposits on the shelf shows that the Late Pleistocene lowstand attained a minimum of −110 m at 19 000 years BP (McMaster et al ., 1970; Martin, 1977). A synthesis of evidence from the Gulf of Guinea shelf and coast shows a rapid rate of sea‐level rise from −60 m at 12 000 years BP to −5·5 m at 7000 years BP (Martin, 1977; Streif, 1983) and to the present elevation in the Bight of Benin at about 5000 years BP (Germain, 1975; Streif, 1983; Lang & Paradis, 1984).…”

Section: Environmental Settingmentioning

confidence: 99%

Sedimentation in a fluvially infilling, barrier‐bound estuary on a wave‐dominated, microtidal coast: the Ouémé River estuary, Benin, west Africa

Anthony¹,

Oyede

Lang

2002

Sedimentology

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The Ouémé River estuary is located on the seasonally humid tropical coast of Benin, west Africa. A striking feature of this microtidal estuary is the presence of a large sand barrier bounding a 120 km2 circular central basin, Lake Nokoué, that is being infilled by heterogeneous fluvial deposits supplied by a relatively large catchment (50 000 km2). Borehole cores from the lower estuary show basal Pleistocene lowstand alluvial sediments overlain by Holocene transgressive–highstand lagoonal mud and by transgressive to probably early highstand tidal inlet and flood‐tidal delta sand deposited in association with non‐preserved transgressive sand barriers. The change in estuary‐mouth sedimentation from a transgressive barrier‐inlet system to a regressive highstand barrier reflects regional modifications in marine sand supply and in the cross‐barrier tidal flux associated with barrier‐inlet systems. As barrier formation west of the Ouémé River led to an increasingly rectilinear shoreline, the longshore drift cell matured, ensuring voluminous eastward transport of sand from the Volta Delta in Ghana, the major purveyor of sand, to the Ouémé embayment, 200 km east. Concomitantly, the number of tidal inlets, and the tidal flux associated with a hitherto interlinked lagoonal system on this coast, diminished. Complete sealing of Lake Nokoué has produced a large, permanently closed estuary, where tidal intrusion is assured through the interconnected coastal lagoon via an inlet located 60 km east. Since 1885, tides have entered the estuary directly through an artificial outlet cut across the sand barrier. Although precluding the seaward loss of fluvial sediments, permanent estuary‐mouth closure has especially deprived the highstand estuary of marine sand, a potentially important component in estuarine infill on wave‐dominated coasts. In spite of a significant fluvial sediment supply, estuarine infill has been moderate, because of the size of the central basin. Estuarine closure has resulted in two co‐existing highstand sediment suites, with limited admixture, the marine‐derived, estuary‐mouth barrier and upland‐derived back‐barrier sediments. This situation differs from that of mature barrier estuaries characterized by active fluvial‐marine sediment mixing and facies interfingering.

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Continental shelf geomorphic features off Portuguese Guinea, Guinea, and Sierra Leone (West Africa)

Cited by 27 publications

References 7 publications

Ecology of Subtidal Algae on Seasonally Devastated Cobble Substrates off Ghana

Ecology of Subtidal Algae on Seasonally Devastated Cobble Substrates off Ghana

Distribution, abundance and assemblages of decapod crustaceans in waters off Guinea-Bissau (north-west Africa)

Sedimentation in a fluvially infilling, barrier‐bound estuary on a wave‐dominated, microtidal coast: the Ouémé River estuary, Benin, west Africa

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