Depositional Setting of Sandstones from the Oligocene-Miocene Ogwashi-Asaba Formation, Niger Delta Basin, Nigeria: Evidence from Grain Size Analysis and Geochemistry

Autor:	Akpoborie I. Anthony, Ejeh O. Innocent, A. A. Israel Etobro
Rok vydání:	2015
Předmět:	Sedimentary depositional environment Shore geography geography.geographical_feature_category Geochemistry Fluvial Weathering Sedimentary rock Structural basin Turbidity Grain size Geology
Zdroj:	Universal Journal of Geoscience. 3:71-82
ISSN:	2331-9615 2331-9593
DOI:	10.13189/ujg.2015.030301
Popis:	Field observations at freshly exposed quarry sites, grain size analysis, mass spectrometry and statistical methods have been used to determine the depositional setting of sandstones from the Oligocene-Miocene Ogwashi-Asaba Formation. Some of the sandstones are ferruginized and indurated; others are friable, cross-bedded, non-ferruginized, white to yellow to reddish brown on weathering, and show top/bottom mantled pebbles. Textural examination indicates that the sandstones range from fine to coarse sands, with graphic mean grain size of -0.3 to 2.13ɸ. Standard deviation ranges from 0.62 to 1.52ɸ and implies moderately sorted to poorly sorted sediments. Textural indices suggest that most of the sediments were deposited under fluvio-deltaic to shallow marine environment by fluvial and beach processes adjacent to a near shore whirlpool agitating turbidity conditions. Major elemental oxides show SiO2 content > 71% with extreme depletion of mobile oxides such as Na2O, CaO and the ferromagnesian minerals through weathering and sedimentary processes.
Databáze:	OpenAIRE
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