Sedimentological and geochemical study of the Bongongo and Ngol travertines located at the Cameroon Volcanic Line

• Published in: Journal of African earth sciences (1994) Vol. 143; pp. 201 - 214
• Main Authors: Bisse, Salomon Bertrant, Ekomane, Emile, Eyong, John Takem, Ollivier, Vincent, Douville, Eric, Maffo Nganne, Marthe Josiane, Ekoko eric, Bokanda, Bitom, Lucien Dieudonné
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.07.2018; Elsevier
• Subjects: Archaeology and Prehistory; Bongongo; Cameroon Volcanic Line; Carbon and oxygen isotopes; Climatology; Continental interfaces, environment; Earth Sciences; Environmental Sciences; Geochemistry; Geography; Geomorphology; Glaciology; Global Changes; Humanities and Social Sciences; Hydrology; Ngol; Sciences of the Universe; Stratigraphy; Tectonics; Thermogene; Travertine; Carbon and oxygen isotopes; Bongongo; Thermogene; Cameroon Volcanic Line; Ngol; Travertine
• ISSN: 1464-343X; 1879-1956
• DOI: 10.1016/j.jafrearsci.2018.03.028

A sedimentological and geochemical study was carried out on the travertines from Bongongo and Ngol locations along the Cameroon Volcanic Line. This work seeks to ascertain: (1) the origin and typology of the studied travertine deposits, (2) the palaeo-environmental depositional model and (3) the typical characteristic of the hydrothermal system. The distribution and typology of travertine deposits were performed from natural outcrops. Oxygen and carbon stable isotope methods have been employed in the detail study of representative travertine samples from Bongongo and Ngol. The different travertine deposits along Ngol stream valley occur around waterfall/cascade, slopes and pools. At Bongongo the travertine precipitation can be linked to temporal fluctuation of carbonate mineral saturation level in rising thermal fluids and the depth of the boiling zone. The hydrothermal system of Ngol and Bongongo has been clarified using results of geochemical analyses of stable isotope, which can be applied regionally. The studied travertines are characterized by δ18O values from −8.4 to −6.4‰ V-PDB for Ngol and −5.8 to −5.9‰ V-PDB for Bongongo and δ13C values from 0.4 to 0.5‰ V-PDB for Ngol and from 1.1 to 2‰ V-PDB for Bongongo, in accordance with global travertine deposit environments. The values of stable carbon isotopes analyses of Bongongo and Ngol travertines are very far from the isotopic composition of magmatic carbon. Based on the geothermal environment, the high temperature parent solution (31 °C and 49 °C) and stable isotope study, it can be considered that the studied travertine from Bongongo and Ngol are charasteristic of the thermogenic type. •The lithofacies associations identified are waterfall, slope and pool facies.•The studied travetines are in accordance with global travertine deposit environments.•Travertine precipitated at Ngol correspond to a fluvial model deposits.•The Bongongo travertine is favoured during transition from humid to drier conditions.•The Bongongo and Ngol Travertine are characteristic of themogenic type.