Morphometric analysis of pebbles in verification of transport processes and interpretation of palaeoenvironment: A case study from the Ogwashi Formation (Oligocene), Niger Delta Basin, Nigeria

Geologos

article

Ovie B. Ogbe¹  Jerry Osokpor¹  Chukwunomso V. Emelue¹  Azuka Ocheli³ 

[1] Department of Earth Sciences, Federal University of Petroleum Resources;Department of Hydrogeology and Hydrology, Delta State Ministry of Water Resources and Development;Department of Geology, University of Delta

关键词: grain morphometry;    sandstone facies;    bivariate plot;    ternary diagram;    mixed environments;    Oligocene sediments;   

DOI  :  10.14746/logos.2023.29.1.02

学科分类：社会科学、人文和艺术（综合）

来源: Walter de Gruyter GmbH

【 摘 要 】

The present paper discusses a palaeoenvironmental interpretation of the Oligocene Ogwashi Formation (Niger Delta Basin, Nigeria) through morphometric analysis of pebbles, a research method essentially depending on the quantitative evaluation of pebble size and shape which change during transport processes in a range of depositional environments. The relationship of bivariate and ternary-diagram plots of independent functions was determined from freshly exposed sandstone sections in quarries at Ibusa, near Asaba, Nigeria. The grain size of pebbles ranges from fine (11.00 mm) to very coarse (41.33 mm), with a mean size of 21.05 mm (coarse pebbles). A bivariate plot of the flatness index vs maximum projection sphericity index shows 37% of the pebbles to fall within a beach (marine) environment, and 33% within a fluvial environment; the remaining 30% are uncertain. The maximum projection sphericity index vs oblate-prolate index bivariate plot indicates that 47% of pebbles fall within a marine environment and 22% within a fluvial environment, while the remaining 31% are uncertain. The sphericity-form ternary diagram plot shows that the pebbles primarily comprise bladed, platy, very bladed and very platy of near-equal proportions with minor elongate and very elongate stones, which suggests that the pebbles are diverse in origin.

【 授权许可】

CC BY-NC-ND