Application of petrography, geochemistry and palynology of the mid-Ordovician – Pennsylvanian sediments of Tabenken in the investigation of Palaeo-environmental alterations of the Oku massif, North West Cameroon
{"title":"Application of petrography, geochemistry and palynology of the mid-Ordovician – Pennsylvanian sediments of Tabenken in the investigation of Palaeo-environmental alterations of the Oku massif, North West Cameroon","authors":"","doi":"10.1016/j.jafrearsci.2024.105428","DOIUrl":null,"url":null,"abstract":"<div><div>This study is effected on the volcano-sedimentary terrain of Tabenken on the Oku massif. Here is a region predominantly underlain by a granitoid basement of Precambrian age (600 ma), overlain in most parts by alkali basalts, andesites, trachytes and rhyolites. Between the basement and volcanics is sandwiched a discontinuous sequence of sedimentary lithofacies composed of conglomerates, sandstones, claystones, siltstones and patches of coal raising the question of the palaeoenvironment. Petrographic analyses, major and trace element geochemistry and palynological analyses were conducted on samples of sediments. Palynological constituents found include amorphous organic matter, phytoclasts, opaque material and palynomorphs consisting of spores with no pollen grains. The presence of cuticles is environmental indicator for delta sediments while abundance of amorphous organic matter (AOM) suggests deposition in a reducing environment. Petrographic studies reveal two cycles of deposition; L1 and L2 separated by Cenozoic outpours. U/Th ratios for the analyzed samples range from 0.3, 0.06, 0.00 to 0.2 and fall within the range of sediments formed in oxidizing environments. This contrasts evidence from AOM hence suggests sediment input cut across climatic and environmental alterations over a long period of time. Sr/Ba ratios range from 0.08 to 0.25 with an average of 0.18 reflecting fresh water environment; while Rb/Sr ratios range from 0.2, 0.29, 0.33 and 0.45 being low and suggests sediments deposited under warm climatic conditions. Diagram of Roser and Korsch, 1986 reveals deposition in a passive margin while Al<sub>2</sub>O<sub>3</sub>/TiO<sub>2</sub> and Th/Co ratios support sediment input of principally felsic origin with little input from mafic sources.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":null,"pages":null},"PeriodicalIF":2.2000,"publicationDate":"2024-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of African Earth Sciences","FirstCategoryId":"89","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S1464343X24002619","RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"GEOSCIENCES, MULTIDISCIPLINARY","Score":null,"Total":0}
引用次数: 0
Abstract
This study is effected on the volcano-sedimentary terrain of Tabenken on the Oku massif. Here is a region predominantly underlain by a granitoid basement of Precambrian age (600 ma), overlain in most parts by alkali basalts, andesites, trachytes and rhyolites. Between the basement and volcanics is sandwiched a discontinuous sequence of sedimentary lithofacies composed of conglomerates, sandstones, claystones, siltstones and patches of coal raising the question of the palaeoenvironment. Petrographic analyses, major and trace element geochemistry and palynological analyses were conducted on samples of sediments. Palynological constituents found include amorphous organic matter, phytoclasts, opaque material and palynomorphs consisting of spores with no pollen grains. The presence of cuticles is environmental indicator for delta sediments while abundance of amorphous organic matter (AOM) suggests deposition in a reducing environment. Petrographic studies reveal two cycles of deposition; L1 and L2 separated by Cenozoic outpours. U/Th ratios for the analyzed samples range from 0.3, 0.06, 0.00 to 0.2 and fall within the range of sediments formed in oxidizing environments. This contrasts evidence from AOM hence suggests sediment input cut across climatic and environmental alterations over a long period of time. Sr/Ba ratios range from 0.08 to 0.25 with an average of 0.18 reflecting fresh water environment; while Rb/Sr ratios range from 0.2, 0.29, 0.33 and 0.45 being low and suggests sediments deposited under warm climatic conditions. Diagram of Roser and Korsch, 1986 reveals deposition in a passive margin while Al2O3/TiO2 and Th/Co ratios support sediment input of principally felsic origin with little input from mafic sources.
期刊介绍:
The Journal of African Earth Sciences sees itself as the prime geological journal for all aspects of the Earth Sciences about the African plate. Papers dealing with peripheral areas are welcome if they demonstrate a tight link with Africa.
The Journal publishes high quality, peer-reviewed scientific papers. It is devoted primarily to research papers but short communications relating to new developments of broad interest, reviews and book reviews will also be considered. Papers must have international appeal and should present work of more regional than local significance and dealing with well identified and justified scientific questions. Specialised technical papers, analytical or exploration reports must be avoided. Papers on applied geology should preferably be linked to such core disciplines and must be addressed to a more general geoscientific audience.