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Robert Frei - One of the best experts on this subject based on the ideXlab platform.
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the pan african west Congo belt in the republic of Congo Congo Brazzaville stratigraphy of the mayombe and west Congo supergroups studied by detrital zircon geochronology
Precambrian Research, 2016Co-Authors: Pascal Affaton, Feiko Kalsbeek, Florent Boudzoumou, Roland Trompette, Kristine Thrane, Robert FreiAbstract:Abstract The African part of the Neoproterozoic Aracuai-West Congo orogen forms a more than 1400 km long belt, running from Gabon in the north to Angola in the south, parallel to the South Atlantic coast. It consists of the West Congo fold belt in the west and a largely undeformed sedimentary foreland basin in the east. In the Republic of Congo (Congo Brazzaville) these are known as, respectively, the ‘Mayombe fold belt’ and the ‘Niari basin’. The Mayombe fold belt is largely made up of strongly deformed metasedimentary rocks of the Mayombe Supergroup and its reworked granitoid basement complex. The Niari basin comprises the sedimentary strata of the West Congo Supergroup, which contain a unit of diamictite and associated cap-carbonate, related to the Marinoan (ca. 635 Ma) glaciation. In this paper detrital zircon U–Pb data are employed to investigate the relationships between the Mayombe and West Congo Supergroups in Congo Brazzaville, as well as the relationships with similar stratigraphic units in the Democratic Republic of Congo (DR Congo). Unfortunately, major differences in stratigraphical nomenclature exist between Congo Brazzaville and DR Congo which, together with geological differences, complicate comparisons. The terminology used in this paper follows the Congo Brazzaville tradition. U–Pb data have been obtained by LA-ICP-MS on 1674 zircon grains from samples of the Mayombe and West Congo Supergroups (seven and eight samples, respectively). Two of the samples have Palaeoproterozoic ages. The other samples are of Neoproterozoic age. Zircons from the latter fall into four main age groups: Group 1, 500–800 Ma, forming 8% of the total population; Group 2, 900–1200 Ma (29%); Group 3, 1800–2300 Ma (19%); and Group 4, 2500–3100 Ma (31%). Only ca. 13% of the zircons fall outside of these groups. Most zircons of Group 1 (600–800 Ma) are interpreted to have been derived from late Neoproterozoic magmatic arc rocks and syn- to post-collisional granites of the Aracuai orogen in Brazil, since rocks of these ages are rare in the Congo craton to the east. Most of Group 2 zircons have probably been derived from early Neoproterozoic (1000–900 Ma) rhyolitic and granitic rocks exposed in DR Congo. The Palaeoproterozoic and Archaean zircons of Groups 3 and 4 may have been derived both from eastern and western source regions. None of the stratigraphical units beneath the Marinoan diamictite contain the 500–800 Ma zircons of Group 1. This is interpreted to indicate deposition of these units during the earlier Neoproterozoic rift and drift phases in the history of the Aracuai-West Congo orogen, while the strata that do contain Group 1 zircons were deposited during the collisional phases and post-collisional uplift. A significant hiatus is likely to be present beneath the Marinoan diamictite. Based on these results, a revision of the stratigraphy of the Mayombe and West Congo Supergroups is recommended. Three granitoid rocks and two metasedimentary samples from the reworked basement complex have also been investigated, yielding Palaeoproterozoic ages, 2050–2100 Ma for the granites, and Palaeoproterozoic and Archaean detrital zircon ages for the metasedimentary rocks. Sm–Nd isotope data have been obtained on a number of (meta-)argilitic and siltstone samples. All samples yielded Palaeoproterozoic model ages, indicating mixing of sediments of different ages, as also observed in the zircon age distributions.
Pascal Affaton - One of the best experts on this subject based on the ideXlab platform.
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the pan african west Congo belt in the republic of Congo Congo Brazzaville stratigraphy of the mayombe and west Congo supergroups studied by detrital zircon geochronology
Precambrian Research, 2016Co-Authors: Pascal Affaton, Feiko Kalsbeek, Florent Boudzoumou, Roland Trompette, Kristine Thrane, Robert FreiAbstract:Abstract The African part of the Neoproterozoic Aracuai-West Congo orogen forms a more than 1400 km long belt, running from Gabon in the north to Angola in the south, parallel to the South Atlantic coast. It consists of the West Congo fold belt in the west and a largely undeformed sedimentary foreland basin in the east. In the Republic of Congo (Congo Brazzaville) these are known as, respectively, the ‘Mayombe fold belt’ and the ‘Niari basin’. The Mayombe fold belt is largely made up of strongly deformed metasedimentary rocks of the Mayombe Supergroup and its reworked granitoid basement complex. The Niari basin comprises the sedimentary strata of the West Congo Supergroup, which contain a unit of diamictite and associated cap-carbonate, related to the Marinoan (ca. 635 Ma) glaciation. In this paper detrital zircon U–Pb data are employed to investigate the relationships between the Mayombe and West Congo Supergroups in Congo Brazzaville, as well as the relationships with similar stratigraphic units in the Democratic Republic of Congo (DR Congo). Unfortunately, major differences in stratigraphical nomenclature exist between Congo Brazzaville and DR Congo which, together with geological differences, complicate comparisons. The terminology used in this paper follows the Congo Brazzaville tradition. U–Pb data have been obtained by LA-ICP-MS on 1674 zircon grains from samples of the Mayombe and West Congo Supergroups (seven and eight samples, respectively). Two of the samples have Palaeoproterozoic ages. The other samples are of Neoproterozoic age. Zircons from the latter fall into four main age groups: Group 1, 500–800 Ma, forming 8% of the total population; Group 2, 900–1200 Ma (29%); Group 3, 1800–2300 Ma (19%); and Group 4, 2500–3100 Ma (31%). Only ca. 13% of the zircons fall outside of these groups. Most zircons of Group 1 (600–800 Ma) are interpreted to have been derived from late Neoproterozoic magmatic arc rocks and syn- to post-collisional granites of the Aracuai orogen in Brazil, since rocks of these ages are rare in the Congo craton to the east. Most of Group 2 zircons have probably been derived from early Neoproterozoic (1000–900 Ma) rhyolitic and granitic rocks exposed in DR Congo. The Palaeoproterozoic and Archaean zircons of Groups 3 and 4 may have been derived both from eastern and western source regions. None of the stratigraphical units beneath the Marinoan diamictite contain the 500–800 Ma zircons of Group 1. This is interpreted to indicate deposition of these units during the earlier Neoproterozoic rift and drift phases in the history of the Aracuai-West Congo orogen, while the strata that do contain Group 1 zircons were deposited during the collisional phases and post-collisional uplift. A significant hiatus is likely to be present beneath the Marinoan diamictite. Based on these results, a revision of the stratigraphy of the Mayombe and West Congo Supergroups is recommended. Three granitoid rocks and two metasedimentary samples from the reworked basement complex have also been investigated, yielding Palaeoproterozoic ages, 2050–2100 Ma for the granites, and Palaeoproterozoic and Archaean detrital zircon ages for the metasedimentary rocks. Sm–Nd isotope data have been obtained on a number of (meta-)argilitic and siltstone samples. All samples yielded Palaeoproterozoic model ages, indicating mixing of sediments of different ages, as also observed in the zircon age distributions.
D Nganga - One of the best experts on this subject based on the ideXlab platform.
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Hydrogeological Information System Elaboration of Coastal Aquifer AQ-2 of Pointe-Noire, in the South-west of Congo-Brazzaville
British Journal of Applied Science and Technology, 2014Co-Authors: G. Moukandi Nkaya, R. R. Niere, B. Mabiala, C. Tathy, D. Nkounkou Tomodiatounga, D NgangaAbstract:The region of Pointe-Noire (south-west of Congo-Brazzaville) located on a coastal sedimentary basin of about 6 000 km 2 is primarily formed by unconsolidated rocks with very little interstice porosity. It is made by a complex multi -aquifers system interconnected. Previous studies have highlighted the lack of data and the need to acquire a better knowledge of the groundwater resource in Pointe Noire. This study intends to represent and schematize the functions of the reservoir and the hydrodynamic behaviour of aquifer AQ-2. A Hydrogeological Information System ( HIS) of aquifer AQ-2 is drawn up from historical reconstitution of the piezometricheads data carried out of various series of measurements from boreholes and piezometers .Two hydrological zones related to the topography and/or relief of study zone were id entified: a zone of the littoral plain, characterized by protuberances and a strong depth of piezometric surface with hydraulic gradient of 0.03, revealing a flow of significant rate and an average permeability which represents a drainage weaker than the r echarge; and a zone of the
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rainfall and temperature variations over Congo Brazzaville between 1950 and 1998
Theoretical and Applied Climatology, 2008Co-Authors: G Samba, D Nganga, M MpounzaAbstract:Trend and discontinuities in rainfall and temperature time series for Congo-Brazzaville are analysed over the period 1950–1998. Rainfall series show a stationary evolution in the south, and an overall negative trend in the north, while temperature series present an irregular increase. This increase is in relation with observations at the regional scale. After a stationary period, a main discontinuity occurred between 1968 and 1970, followed by a second at the beginning of the 1980s. However, the differences are observed between large towns (Brazzaville and Pointe-Noire), and small towns (Dolisie, Sibiti, Impfondo).
Florent Boudzoumou - One of the best experts on this subject based on the ideXlab platform.
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the pan african west Congo belt in the republic of Congo Congo Brazzaville stratigraphy of the mayombe and west Congo supergroups studied by detrital zircon geochronology
Precambrian Research, 2016Co-Authors: Pascal Affaton, Feiko Kalsbeek, Florent Boudzoumou, Roland Trompette, Kristine Thrane, Robert FreiAbstract:Abstract The African part of the Neoproterozoic Aracuai-West Congo orogen forms a more than 1400 km long belt, running from Gabon in the north to Angola in the south, parallel to the South Atlantic coast. It consists of the West Congo fold belt in the west and a largely undeformed sedimentary foreland basin in the east. In the Republic of Congo (Congo Brazzaville) these are known as, respectively, the ‘Mayombe fold belt’ and the ‘Niari basin’. The Mayombe fold belt is largely made up of strongly deformed metasedimentary rocks of the Mayombe Supergroup and its reworked granitoid basement complex. The Niari basin comprises the sedimentary strata of the West Congo Supergroup, which contain a unit of diamictite and associated cap-carbonate, related to the Marinoan (ca. 635 Ma) glaciation. In this paper detrital zircon U–Pb data are employed to investigate the relationships between the Mayombe and West Congo Supergroups in Congo Brazzaville, as well as the relationships with similar stratigraphic units in the Democratic Republic of Congo (DR Congo). Unfortunately, major differences in stratigraphical nomenclature exist between Congo Brazzaville and DR Congo which, together with geological differences, complicate comparisons. The terminology used in this paper follows the Congo Brazzaville tradition. U–Pb data have been obtained by LA-ICP-MS on 1674 zircon grains from samples of the Mayombe and West Congo Supergroups (seven and eight samples, respectively). Two of the samples have Palaeoproterozoic ages. The other samples are of Neoproterozoic age. Zircons from the latter fall into four main age groups: Group 1, 500–800 Ma, forming 8% of the total population; Group 2, 900–1200 Ma (29%); Group 3, 1800–2300 Ma (19%); and Group 4, 2500–3100 Ma (31%). Only ca. 13% of the zircons fall outside of these groups. Most zircons of Group 1 (600–800 Ma) are interpreted to have been derived from late Neoproterozoic magmatic arc rocks and syn- to post-collisional granites of the Aracuai orogen in Brazil, since rocks of these ages are rare in the Congo craton to the east. Most of Group 2 zircons have probably been derived from early Neoproterozoic (1000–900 Ma) rhyolitic and granitic rocks exposed in DR Congo. The Palaeoproterozoic and Archaean zircons of Groups 3 and 4 may have been derived both from eastern and western source regions. None of the stratigraphical units beneath the Marinoan diamictite contain the 500–800 Ma zircons of Group 1. This is interpreted to indicate deposition of these units during the earlier Neoproterozoic rift and drift phases in the history of the Aracuai-West Congo orogen, while the strata that do contain Group 1 zircons were deposited during the collisional phases and post-collisional uplift. A significant hiatus is likely to be present beneath the Marinoan diamictite. Based on these results, a revision of the stratigraphy of the Mayombe and West Congo Supergroups is recommended. Three granitoid rocks and two metasedimentary samples from the reworked basement complex have also been investigated, yielding Palaeoproterozoic ages, 2050–2100 Ma for the granites, and Palaeoproterozoic and Archaean detrital zircon ages for the metasedimentary rocks. Sm–Nd isotope data have been obtained on a number of (meta-)argilitic and siltstone samples. All samples yielded Palaeoproterozoic model ages, indicating mixing of sediments of different ages, as also observed in the zircon age distributions.
Roland Trompette - One of the best experts on this subject based on the ideXlab platform.
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the pan african west Congo belt in the republic of Congo Congo Brazzaville stratigraphy of the mayombe and west Congo supergroups studied by detrital zircon geochronology
Precambrian Research, 2016Co-Authors: Pascal Affaton, Feiko Kalsbeek, Florent Boudzoumou, Roland Trompette, Kristine Thrane, Robert FreiAbstract:Abstract The African part of the Neoproterozoic Aracuai-West Congo orogen forms a more than 1400 km long belt, running from Gabon in the north to Angola in the south, parallel to the South Atlantic coast. It consists of the West Congo fold belt in the west and a largely undeformed sedimentary foreland basin in the east. In the Republic of Congo (Congo Brazzaville) these are known as, respectively, the ‘Mayombe fold belt’ and the ‘Niari basin’. The Mayombe fold belt is largely made up of strongly deformed metasedimentary rocks of the Mayombe Supergroup and its reworked granitoid basement complex. The Niari basin comprises the sedimentary strata of the West Congo Supergroup, which contain a unit of diamictite and associated cap-carbonate, related to the Marinoan (ca. 635 Ma) glaciation. In this paper detrital zircon U–Pb data are employed to investigate the relationships between the Mayombe and West Congo Supergroups in Congo Brazzaville, as well as the relationships with similar stratigraphic units in the Democratic Republic of Congo (DR Congo). Unfortunately, major differences in stratigraphical nomenclature exist between Congo Brazzaville and DR Congo which, together with geological differences, complicate comparisons. The terminology used in this paper follows the Congo Brazzaville tradition. U–Pb data have been obtained by LA-ICP-MS on 1674 zircon grains from samples of the Mayombe and West Congo Supergroups (seven and eight samples, respectively). Two of the samples have Palaeoproterozoic ages. The other samples are of Neoproterozoic age. Zircons from the latter fall into four main age groups: Group 1, 500–800 Ma, forming 8% of the total population; Group 2, 900–1200 Ma (29%); Group 3, 1800–2300 Ma (19%); and Group 4, 2500–3100 Ma (31%). Only ca. 13% of the zircons fall outside of these groups. Most zircons of Group 1 (600–800 Ma) are interpreted to have been derived from late Neoproterozoic magmatic arc rocks and syn- to post-collisional granites of the Aracuai orogen in Brazil, since rocks of these ages are rare in the Congo craton to the east. Most of Group 2 zircons have probably been derived from early Neoproterozoic (1000–900 Ma) rhyolitic and granitic rocks exposed in DR Congo. The Palaeoproterozoic and Archaean zircons of Groups 3 and 4 may have been derived both from eastern and western source regions. None of the stratigraphical units beneath the Marinoan diamictite contain the 500–800 Ma zircons of Group 1. This is interpreted to indicate deposition of these units during the earlier Neoproterozoic rift and drift phases in the history of the Aracuai-West Congo orogen, while the strata that do contain Group 1 zircons were deposited during the collisional phases and post-collisional uplift. A significant hiatus is likely to be present beneath the Marinoan diamictite. Based on these results, a revision of the stratigraphy of the Mayombe and West Congo Supergroups is recommended. Three granitoid rocks and two metasedimentary samples from the reworked basement complex have also been investigated, yielding Palaeoproterozoic ages, 2050–2100 Ma for the granites, and Palaeoproterozoic and Archaean detrital zircon ages for the metasedimentary rocks. Sm–Nd isotope data have been obtained on a number of (meta-)argilitic and siltstone samples. All samples yielded Palaeoproterozoic model ages, indicating mixing of sediments of different ages, as also observed in the zircon age distributions.