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Figure 8: Ternary diagram showing the pebble ratios in the Study Area (After Sneed and Folks, 1958)

Figure 8 Ternary diagram showing the pebble ratios in the Study Area (After Sneed and Folks, 1958)

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Figure 1: Location map of the study area (after U.S.A Survey Agency, 2010) To describe the geology and establish the paleoenvironment of the Bima sandstone, thorough field mapping and sampling were done in the study area. The study area (Dumne and its environs) is situated in Song Local Government Area of Adamawa State (Fig. 1). In order to better understand the lithostratigraphic unit and depositional environment, the study aim to combine outcrop data with statistical parameters from granulometry (Mean Mz; Standard Deviation 61; Skewness Ski; and Kurtosis K) and pebble morphometric indices (Elongation Ratio ER; Coefficient of Flatness CFI; Maximum Projection Sphericity Index MPSI and Oblate- Prolate Index OPI).
Figure 1: Location map of the study area (after U.S.A Survey Agency, 2010) To describe the geology and establish the paleoenvironment of the Bima sandstone, thorough field mapping and sampling were done in the study area. The study area (Dumne and its environs) is situated in Song Local Government Area of Adamawa State (Fig. 1). In order to better understand the lithostratigraphic unit and depositional environment, the study aim to combine outcrop data with statistical parameters from granulometry (Mean Mz; Standard Deviation 61; Skewness Ski; and Kurtosis K) and pebble morphometric indices (Elongation Ratio ER; Coefficient of Flatness CFI; Maximum Projection Sphericity Index MPSI and Oblate- Prolate Index OPI).
Figure 2: The Stratigraphic Succession of the Upper Benue Trough (adopted from Finthan and Mamman, 2020). Samples obtained were subjected to Grain size analysis. A mortar and rubber-padded pestle was used to disaggregate the six (6) chosen representative samples after they had been air dried. Then, using the Ro-tap mechanical shaker, they were weighed and sieved for particle- size distribution in accordance with established standards. On an arithmetic graph, grain size distribution plots.
Figure 2: The Stratigraphic Succession of the Upper Benue Trough (adopted from Finthan and Mamman, 2020). Samples obtained were subjected to Grain size analysis. A mortar and rubber-padded pestle was used to disaggregate the six (6) chosen representative samples after they had been air dried. Then, using the Ro-tap mechanical shaker, they were weighed and sieved for particle- size distribution in accordance with established standards. On an arithmetic graph, grain size distribution plots.
Figure 3: Lithostratigraphic section of the Study Area Sedimentological study of Bima Sandstone in Dumne and Environs, Yola Sub-basin, Upper Benue Trough, Northeastern Nigeria. Gravel dominated facies Gmm Facies:
Figure 3: Lithostratigraphic section of the Study Area Sedimentological study of Bima Sandstone in Dumne and Environs, Yola Sub-basin, Upper Benue Trough, Northeastern Nigeria. Gravel dominated facies Gmm Facies:
Table 1: Percentile values from the graphic plot Table 2: Result of Mean, Standard Deviation, Skewness and Kurtosis of Samples analyzed Using Graphic Method
Table 1: Percentile values from the graphic plot Table 2: Result of Mean, Standard Deviation, Skewness and Kurtosis of Samples analyzed Using Graphic Method
Table 3: Summary of Granulometric results and description (After Folk and Ward, 1957) These values point to a poor sorting (Folk and Ward, 1957; Ocheli et al., 2018). Poor sorting indicates fluvial-continental settings for the deposition of the sediments (Friedman, 1967; Fithan et al., 2022). The range of the kurtosis value is 0.84 to 1.43, with an average of 1.11. On the basis of this, it ranges from platykurtic to leptokurtic, and on the average the sandstones are leptokurtic. The skewness values range between 0.08 - 0.28 with an average value of 0.17. Blatt et al. (1991) described the skewness ranges as positively skewed to nearly symmetrical. The sandstones are positively skewed based on the average.
Table 3: Summary of Granulometric results and description (After Folk and Ward, 1957) These values point to a poor sorting (Folk and Ward, 1957; Ocheli et al., 2018). Poor sorting indicates fluvial-continental settings for the deposition of the sediments (Friedman, 1967; Fithan et al., 2022). The range of the kurtosis value is 0.84 to 1.43, with an average of 1.11. On the basis of this, it ranges from platykurtic to leptokurtic, and on the average the sandstones are leptokurtic. The skewness values range between 0.08 - 0.28 with an average value of 0.17. Blatt et al. (1991) described the skewness ranges as positively skewed to nearly symmetrical. The sandstones are positively skewed based on the average.
Table 4: Multivariate discriminant results and their interpretation
Table 4: Multivariate discriminant results and their interpretation
Figure 4: Bivariate plot of mean against standard deviation (After Moiola and Weiser, 1968) Sedimentological study of Bima Sandstone in Dumne and Environs, Yola Sub-basin, Upper Benue Trough, Northeastern Nigeria.
Figure 4: Bivariate plot of mean against standard deviation (After Moiola and Weiser, 1968) Sedimentological study of Bima Sandstone in Dumne and Environs, Yola Sub-basin, Upper Benue Trough, Northeastern Nigeria.
Figure 5: Bivariate plot of skewness against standard deviation (After Friedman, 1967)
Figure 5: Bivariate plot of skewness against standard deviation (After Friedman, 1967)
Table 5: Pebble form parameters, range values, mean values and their interpretations
Table 5: Pebble form parameters, range values, mean values and their interpretations
Figure 6: Coefficient of Flatness ratio against Maximum projection sphericity index (After Stratten, 1974 Using the Tri-Plot program (Graham and Migley, 2000), each analyzed pebble was plotted on a Sneed and Folk (1958) diagram (Fig. 8), and the percentages of the form classes were calculated (Tab. 6). According to the analysis of the form indices, compact-bladed, compact- platy, compact-elongated, and compact make up 85% of the identified Sneed and Folk, (1958) shape classifications that environment. Fluvial environments are characterized by com plots. Dobkins and Folk (1970) are representative of specific pact (C), compact-bladed (CB), compact-platy (CP), and compact-elongated (CE); transitional environments are characterized by platy (P), bladed (B), and elongated (E); and beach environments are characterized by very platy (VP), very bladed (VB), and very elongated (VE). 1 This led to conclude that the investigated pebbles' form indices were shaped in a fluvial environment. The greater proportion of pebbles that show evidence of fluvial action supported the fluvial processes' dominance.
Figure 6: Coefficient of Flatness ratio against Maximum projection sphericity index (After Stratten, 1974 Using the Tri-Plot program (Graham and Migley, 2000), each analyzed pebble was plotted on a Sneed and Folk (1958) diagram (Fig. 8), and the percentages of the form classes were calculated (Tab. 6). According to the analysis of the form indices, compact-bladed, compact- platy, compact-elongated, and compact make up 85% of the identified Sneed and Folk, (1958) shape classifications that environment. Fluvial environments are characterized by com plots. Dobkins and Folk (1970) are representative of specific pact (C), compact-bladed (CB), compact-platy (CP), and compact-elongated (CE); transitional environments are characterized by platy (P), bladed (B), and elongated (E); and beach environments are characterized by very platy (VP), very bladed (VB), and very elongated (VE). 1 This led to conclude that the investigated pebbles' form indices were shaped in a fluvial environment. The greater proportion of pebbles that show evidence of fluvial action supported the fluvial processes' dominance.
Figure 7: Roundness against Elongation ratio (ER) of the pebbles (After Sames, 1966)
Figure 7: Roundness against Elongation ratio (ER) of the pebbles (After Sames, 1966)
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