Sedimentological Study of Alluvial Deposits on the Congolese Coast: Highlighting the Erosive Character of the Holocene Wet Climatic Phases  

作　　者：Hilaire Elenga Nehl Dorland Kobawila Dieudonne Maurice Malounguila-Nganga Malanda Nimy Edmond Nicaise Giresse Pierre Hilaire Elenga;Nehl Dorland Kobawila;Dieudonne Maurice Malounguila-Nganga;Malanda Nimy Edmond Nicaise;Giresse Pierre(Geosciences Laboratory, Faculty of Science and Technology, Marien Ngouabi University, Brazzaville, Congo;Geological and Mining Research Center (CRGM), Brazzaville, Congo;Center for Training and Research on Mediterranean Environments (CEFREM), University via Dominitia, Perpignan, France)

机构地区：[1]Geosciences Laboratory, Faculty of Science and Technology, Marien Ngouabi University, Brazzaville, Congo [2]Geological and Mining Research Center (CRGM), Brazzaville, Congo [3]Center for Training and Research on Mediterranean Environments (CEFREM), University via Dominitia, Perpignan, France

出　　处：《Open Journal of Geology》2023年第1期1-22,共22页地质学期刊（英文）

摘　　要：A granulometric, mineralogical, morphoscopic and exoscopic study and Rock-Eval analysis carried out on samples taken in the Loango Bay and at Kivesso on the Congolese coast have made it possible to highlight the highly erosive character of the well-documented wet phases ca 9000 - 3000 years B.P. and ca 320 B.P. in the sub-region. Supported by carbon-14 dating, total organic carbon analyses highlight two major phases of peat deposit emplacement. The first, ca. 7000 years B.P., corresponds to the beginning of the deposition of the yellow formation in the entire Loango Bay;the second, ca. 320 years B.P., is contemporary with the deposition of peat in the Kivesso sector. The granulometric analysis of the sediments shows that they are essentially sandy-clay and very poor in silt, alternating with beds of silty clay sometimes rich in organic matter. These sands have a predominant mode of 0.200 mm and an average varying between 0.150 and 0.300 mm. They constitute the flood phase of the carrier current. They are associated with a population of mode 0.125 mm sometimes 0.050 mm with an average varying between 0.100 mm and 0.126 mm which corresponds to the settling phase. Morphoscopic examination showed several varieties of quartz that argue for a source of supply close to the depositional sites.A granulometric, mineralogical, morphoscopic and exoscopic study and Rock-Eval analysis carried out on samples taken in the Loango Bay and at Kivesso on the Congolese coast have made it possible to highlight the highly erosive character of the well-documented wet phases ca 9000 - 3000 years B.P. and ca 320 B.P. in the sub-region. Supported by carbon-14 dating, total organic carbon analyses highlight two major phases of peat deposit emplacement. The first, ca. 7000 years B.P., corresponds to the beginning of the deposition of the yellow formation in the entire Loango Bay;the second, ca. 320 years B.P., is contemporary with the deposition of peat in the Kivesso sector. The granulometric analysis of the sediments shows that they are essentially sandy-clay and very poor in silt, alternating with beds of silty clay sometimes rich in organic matter. These sands have a predominant mode of 0.200 mm and an average varying between 0.150 and 0.300 mm. They constitute the flood phase of the carrier current. They are associated with a population of mode 0.125 mm sometimes 0.050 mm with an average varying between 0.100 mm and 0.126 mm which corresponds to the settling phase. Morphoscopic examination showed several varieties of quartz that argue for a source of supply close to the depositional sites.

关 键 词：HOLOCENE PALEOCLIMATES PALEOENVIRONMENTS Loango Bay SEDIMENTOLOGY 

分 类 号：P53[天文地球—古生物学与地层学]