Phosphates du Protérozoïque supérieur dans la chaîne des Dahomeyides (circa 600 Ma) de la région de Bassar (Nord-Togo, Afrique de l'Ouest

Blot, Alain; Affaton, Pascal; Seddoh, K. F.; Aregba, A.; Godonou, Senyo K.; Lenoir, François; Drouet, Jean-Jacques; Simpara, N; Magat, Philippe

doi:10.1016/0899-5362(88)90062-0

Cited by 14 publications

(9 citation statements)

References 3 publications

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“…Blot et al . (), Bertrand‐Sarfati et al . () and Flicoteaux & Trompette () reported the occurrence of Ediacaran phosphorites in peripheral parts of the Taoudeni Basin (West African craton).…”

Section: Geodynamic Climatic and Chemical Controls On Phosphogenesismentioning

confidence: 96%

“…Phosphorites from this time interval are well‐known in many palaeogeographic areas, such as the Siberian Platform (Ilyin, ,b), the West African craton (Blot et al ., ; Bertrand‐Sarfati et al ., ; Flicoteaux & Trompette, ), China (Chen et al ., ; Jiang et al ., ; Ling et al ., ), Australia (Creveling et al ., ) and India (Banerjee et al ., ; Mazumdar et al ., ). Other areas of economic and subeconomic interest have been less studied, such as those located along the western margins of Gondwana and Baltica (Andersson, ; Notholt & Brasier, ; Wallin, ).…”

Section: Introductionmentioning

confidence: 99%

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Ediacaran–Cambrian phosphorites from the western margins of Gondwana and Baltica

et al. 2015

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The late Ediacaran–mid Cambrian occurrences of phosphorites in the western Mediterranean region (West Gondwana) and southern Sweden (north‐west Baltica) are related to the poleward drift of West Gondwana and the northern drift of Baltica. As a result, these regions crossed subtropical and temperate palaeolatitudes of the Southern Hemisphere, in which oceanic upwelling and high organic productivity were the probable sources of phosphorus along their western margins. A parallel south‐west/north‐east migration trend of evaporites and delayed, time transgressive phosphorites point to distal upwelling environments associated with shallower arid conditions. Concentration of hardground‐derived phosphate accumulations took place by repeated alternations of low sedimentation rates and condensation, in situ early diagenetic and microbially mediated precipitation of amorphous and cryptocrystalline, carbonate‐bearing francolite, winnowing and polyphase reworking of previously phosphatized skeletons and hardground‐derived clasts. Thicker phosphorites of economic importance display a spiculate sponge‐thromboid consortium that points to a distinct benthic community developed on suboxic, slope to basinal substrates. For most phosphorite samples an up to ten‐fold enrichment in rare earth element concentration relative to post‐Archaean average Australian shale reflects significant incorporation of rare earth elements and yttrium after deposition. Considerable scavenging took place from anoxic pore waters, following reductive dissolution of iron oxides as evidenced from the medium rare earth element enrichment in most samples. This contrasts with the rare preservation of primary sea water features, such as cerium depletion and yttrium enrichment, in phosphatized thrombolites from the shallower realms (for example, Montagne Noire). The data are consistent with phosphogenesis after upwelling and transgression of nutrient‐rich, suboxic–anoxic, ferruginous waters over more oxygenated, rifting settings and inland portions of an evolving passive margin.

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Section: Geodynamic Climatic and Chemical Controls On Phosphogenesismentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Ediacaran–Cambrian phosphorites from the western margins of Gondwana and Baltica

et al. 2015

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“…Within its lower part are several hundred metres of diamictites and coarse detrital rocks, considered as the marine equivalent of the Triad of the Pendjari megasequence. These glaciomarine deposits contain hematitic microconglomerates, lenses of carbonate rocks, thin layers of bedded chert or banded iron formation, phosphorite beds, and rare mafic volcanic flows (Trompette, 1981;Simpara et al, 1985;Blot et al, 1988;Affaton, 1990). The volcanic flows include alkaline lavas and tholeites of MORB-type dated at about 624 Ma (KAr whole rock age, Bozhko et al, 1971).…”

Section: Structural Units Of the Dahomeyide Beltmentioning

confidence: 99%

Pan-African tectonic evolution and glacial events registered in Neoproterozoic to Cambrian cratonic and foreland basins of West Africa

Deynoux

Affaton

Trompette³

et al. 2006

Journal of African Earth Sciences

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144

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“…The FMNP comprises Mt Fazao (861 m), Mt Malfakassa (713 m) and plains where Mo River flows. These mountains are part of the Atacora chain, which was formed during the pan African orogenesis [ 32 ]. The region has a unimodal rainfall regime, with most rains falling in April-October.…”

Section: Study Areamentioning

confidence: 99%

Changes in the West African forest-savanna mosaic, insights from central Togo

et al. 2018

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The West African forest-savanna mosaic, an important habitat for biodiversity and humans, is severely degraded, fragmented and modified by human activities. However, few studies have quantified the land cover changes observed over time and/or analysed the drivers of change. This study focused on Fazao-Malfakassa National Park, the largest in Togo, uses a combination of remote sensing, ground surveys and questionnaires to: (i) quantify vegetation changes, (ii) determine the drivers of change, (iii) compare results with findings elsewhere in the region and (iv) suggest management interventions. The images used were Landsat 5 TM, Landsat 7 ETM and Sentinel-2. Different vegetation indices were computed including: number of fragments, index of dominance, mean area of a vegetation type and mean annual expansion rate. In total, 300 people (including park staff and local populations) were interviewed using a semi-structured questionnaire. Results indicate that between 1987 and 2015 closed-canopy forest and tree-savanna became severely degraded and fragmented, following trends in other parts of the West African forest-savanna mosaic. The main drivers of change were agricultural expansion, bush fires and timber extraction. Observed changes and drivers altered with time: e.g. agricultural expansion was greatest during 1987–2001 (linked with political instability) while illegal timber extraction augmented during 2001–2015 (following increased timber value). Park staff and local populations’ perceptions on drivers of change did not differ. Our study highlights that action is urgently needed if we are to preserve this important habitat, the biodiversity it hosts and the services it provides to humans. We suggest several management interventions, learning from successful interventions elsewhere in the region.

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Phosphates du Protérozoïque supérieur dans la chaîne des Dahomeyides (circa 600 Ma) de la région de Bassar (Nord-Togo, Afrique de l'Ouest

Cited by 14 publications

References 3 publications

Ediacaran–Cambrian phosphorites from the western margins of Gondwana and Baltica

Ediacaran–Cambrian phosphorites from the western margins of Gondwana and Baltica

Pan-African tectonic evolution and glacial events registered in Neoproterozoic to Cambrian cratonic and foreland basins of West Africa

Changes in the West African forest-savanna mosaic, insights from central Togo

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