© 2019, IJSRMS All Rights Reserved 43 International Journal of Scientific Research in _______________________________ Research Paper . Multidisciplinary Studies E-ISSN: 2454-9312 Vol.5, Issue.12, pp.43-51, December (2019) P-ISSN: 2454-6143 Granulometric Analysis Indices As Signatures of The Depositional Environment of The Bima (I) Formation At Wuyo Area, Part of Gongola Sub-Basin, Upper Benue Trough, Northeastern Nigeria I.M. Mustapha 1* , A.S. Sa’ad 2 , H. Muhyideen 3 , T.M. Abubakar 4 1,2 Department of Geology, University of Maiduguri, Borno, Nigeria 3 Department of Geology, Ahmadu Bello University, Zaria, Nigeria 4 Department of Geological Science, Al-Hikmah University Ilorin, Nigeria * Corresponding Author: ibrahim1025m@gmail.com, Tel.: +2347035703977 Available online at: www.isroset.org Received: 09/Dec/2019, Accepted: 12/Dec/2019, Online: 31/Dec/2019 Abstract— The Benue Trough is a major NE-SW trending rift basin of 50-150km width. It extends for over 1000km, starting from the northern margin of the Chad Basin in the north. The trough is a sedimentary basin of up to 6000m of Cretaceous to Tertiary sediments associated with volcanic rocks. It is geographically sub-divided into lower, middle and upper portions. The textural parameters computed from granulometric analysis of the Bima (I) i.e. graphical mean size, standard deviation, skewness and kurtosis yielded values ranging from 0.10 Ф -1.20 Ф, 0.624 Φ to 1.29 Φ, 0.073Ф - 0.666 Ф and 1.08 Φ - 1.55 Φ respectively. The granulometric analysis indicated that the Bima (I) is dominantly moderately sorted and are mostly positively skewed. The bivariate plots of mean versus first percentile, standard deviation versus first percentile and mean versus standard deviation of the representative samples of the Bima (I) at the Wuyo area showed mainly fluvial environments. The probability curve plots all showed two sand population which is indicative of fluvial environment of deposition. The study is significant in providing evidence for the fluvial (braided stream) origin of the Bima (I) Formation. Keywords—Benue Trough, Bima (I) Formation, Granulometric analysis, Bivariate plots, Fluvial origin. I. INTRODUCTION Bima Sandstone is the name given to the continental intercalaire in the Chad Basin and Upper Benue Trough of Nigeria. It is the oldest sedimentary deposit in these regions. The composition of Bima Sandstone mainly arkose to quartz arenite and its depositional structures have generated wide speculations as to the source and environment of deposition. The Early Cretaceous continental Bima Sandstone (which is the formation of concern) unconformably overlies the Pan African basement rocks. In most places it represents by far the greatest proportion of the lithostratigraphic succession in the Upper Benue Trough. The Formation is divided into three siliciclastic members: lower (B1); middle (B2) and upper (B3) members. Grain size is the most fundamental property of sediment particles, affecting their entrainment, transport and deposition. Grain size analysis therefore provides important clues to the sediment provenance, transport history and depositional conditions [19]. This research is aimed at determining the origin of the sediments, using results from the sieve analysis, together with other evidences from lithofacies analysis to infer the transportation history and delineate the paleoenvironment of deposition of the Bima (I) Formation exposed at Wuyo area of Gombe State. STUDY AREA The study area is located in Wuyo town in Borno State and the studied section lies between latitude 10 0 15' N and longitude 11 0 12' E (Figure 1). It is characterised by undulating terrain with few flat plains. The climate is semi- arid with three distinct seasons; a long hot dry season from April to May. Day time temperatures are in the range of 36 0 to 40 0 C and night time temperatures fall to 10 0 to 17 0 C. This is followed by a short rainy season from May to September with a daily minimum temperature of 20 0 C and a maximum of 31 0 C with relative humidity of 40 to 60% and annual rainfall from 860 to 900 mm. Finally, the cold (harmattan) season runs from October to March when temperatures fall to about 20 0 C and a dry dusty wind blows from the Sahara desert.