scholarly journals Sedimentology and Paleogeographic Synthesis of Cretaceous Sediments in Auchi Area of Anambra Basin

2020 ◽  
Vol 24 (5) ◽  
pp. 943-974
Author(s):  
O.A. Ilegieuno ◽  
E.J. Ighodaro ◽  
R.O. Sunny
Keyword(s):  
Grain Size ◽  
Sedimentary Rock ◽  
Upper Cretaceous ◽  
High Energy ◽  
Coarse Grained ◽  
Grain Size Analysis ◽  
Size Analysis ◽  
Anambra Basin ◽  
Edo State ◽  
Cretaceous Deposits

The sedimentary rock in the Auchi area of Edo State constitutes part of the Upper Cretaceous Deposits of the Anambra Basin, which has its  depocentre in Eastern Nigeria. Lithostratigraphic and Sedimentological studies carried out on twenty eight (28) selected samples from a section of a road–cut show that the sediments range from fine through medium to coarse grained. Sorting is poor to moderate. Grain size analysis shows that the sediments are strongly fine skewed and they exhibit mesokurtic to platykurtic kurtosis. These coupled with the various colours observed in the sediment, ranging from whitish sand through yellowish brown, pink and reddish brown possibly indicate a non–marine environment and a fluviatile to deltaic environment of sedimentation is suggested. The sediments might have been transported in a fairly high energy medium and deposited under a slightly fluctuating velocity. Keywords: Sedimentology, Cretaceous, Paleogeography, Grain size, Anambra Basin

scholarly journals Sedimentologic, Heavy Mineral and Provenance Studies of the Cretaceous Sediments in the Auchi Area of the Anambra Basin

2020 ◽  
Vol 24 (6) ◽  
pp. 955-959
Author(s):  
O.A. Ilegieuno ◽  
E.J. Ighodaro ◽  
R.O. Sunny
Keyword(s):  
Upper Cretaceous ◽  
Heavy Mineral ◽  
Coarse Grained ◽  
Metamorphic Rocks ◽  
Basement Complex ◽  
Provenance Studies ◽  
Anambra Basin ◽  
Edo State ◽  
Sand Particles ◽  
Cretaceous Deposits

The Upper Cretaceous Deposits of the Anambra Basin has a part of its sedimentary rock deposited in the Auchi area of Edo State. Geologic field and Sedimentological studies carried out on twenty eight (28) selected samples from a section of a road–cut show that the sediments range from fine through medium to coarse grained. Morphoscopic studies reveal subangular to subrounded outline of sand particles. These coupled with the  various colours observed in the sediment, ranging from whitish sand through yellowish brown, pink and reddish brown possibly indicate a non–marine environment and a fluviatile to deltaic environment of sedimentation is suggested. Heavy mineral assemblage made up mainly of opaque, andalusite, zircon, hornblend, sphene and epidote suggest derivation from the Precambrian Igneous and medium to high grade metamorphic rocks of the underlying Basement Complex of Nigeria. Keywords: Sedimentology, Cretaceous, Morphoscopic, Heavy Mineral, Provenance

scholarly journals Grain Size Analysis, Textural Characterisation and Depositional Environment of Turonian Amasiri Sandstone, Southern Benue Trough, Nigeria

2021 ◽  
Vol 4 (2) ◽  
Keyword(s):  
Grain Size ◽  
Depositional Environment ◽  
Function Analysis ◽  
High Energy ◽  
Coarse Grained ◽  
Grain Size Analysis ◽  
Size Analysis ◽  
Benue Trough ◽  
Shallow Marine ◽  
Wide Range

Grain size analysis of Turonian Amasiri Sandstone in southern Benue Trough has been undertaken to determine the controversial depositional environment of the formation. The formation was first studied on outcrops and 26 representative samples were collected and subjected to particle size analysis in line with standard procedures for dry sieving. Various methods of environmental interpretation of grain size distribution data were applied to constrain the depositional of the sandstones. The result indicates that the sands are medium and coarse-grained with mean size ranging from 0.15 to 1.87φ and averaging 0.96 φ. The sandstones are moderately to poorly sorted with standard deviation values ranging from 0.72 to 1.38 φ and averaging 1.07 φ. They exhibit a wide range of distribution from strongly coarse skewed to strongly fine skewed with skewness values ranging from -2.31 to 1.52 φ and averaging -0.04 φ but indicate a narrow range of kurtosis from mesokurtic to leptokurtic distribution with values ranging from 0.99 to 3.49 φ and an average of 2.06 φ. The sediments have bimodal with minor polymodal and unimodal distribution with primary modal size of 1.2 φ. The bivariate plots of size statistical parameters indicate fluvial environment of deposition. However, linear discriminant function analysis and the interpretations of log-probability plots indicate deposition in a fluvial, beach, and shallow marine settings, and thus suggesting a possible deposition in high-energy transitional environment. The C-M pattern of the samples indicates that sediments were transported mainly by rolling and suspension with subordinate fractions moved by rolling as well as suspension. Thus, it is deduced that Amasiri Sandstone was deposited in fluvial, beach, and agitated shallow marine environments.

scholarly journals Grain Size and Heavy Minerals Analysis of Maastrichtian Sandstone, Anambra Basin, Nigeria: Implication for Aquifer Properties

2020 ◽  
Vol 24 (11) ◽  
pp. 1881-1888
Author(s):  
M Ilevbare ◽  
OI Imasuen
Keyword(s):  
Grain Size ◽  
Drinking Water ◽  
Hydraulic Conductivity ◽  
Heavy Minerals ◽  
Grain Size Analysis ◽  
Size Analysis ◽  
Grain Sizes ◽  
Anambra Basin ◽  
Aquifer Geometry ◽  
Aquifer Properties

The Maastrichtian sediments of Anambra Basin, south western Nigeria was studied for grain characteristics and maturity of the sediments, so that by combining sedimentological characteristics, maturity and its paleoenvironment of deposition of the Ajali sandstone, in order to ascertain the aquifer properties of the groundwater within the study area and by extension the availability of drinking water for both the urban and rural settlers. Grain size analysis (51 samples) and heavy mineral analysis (15 samples each) were analyzed. The textural parameters show that the Sandstone are medium sand, poorly to moderately sorted, coarse to strongly coarse skewed with mesokurtic to leptokurtic grains. The heavy minerals present in lithologic sand and sandstone units of Ajali Formation are mainly zircon, rutile, tourmaline, apatite, staurolite, and opaque minerals (Goethite, hematite, ilmenite), these heavy minerals found in the sandstone are associated with igneous and metamorphic source which indicates that these maastritchian sediments are from basement complex rock The ZTR index of 67.96% and the values of the kurtosis indicates a sub-mature sandstone to mature sandstone, which gives an excellent aquifer properties. Also, the paleoenvironment of deposition of the Maastrichtian sediments is Fluvial. The sand and sandstone bodies deposited in a fluvial system have sheet-like geometries and due to the differences in the extent of aquifer compartmentalization, Sandstone deposited in fluvial environment normally has better hydraulic conductivity which again reveals a good aquifer property. The sedimentological characteristics for the Sandstone exposed at Fugar and environs, is a coarsening upward sequence (increasing grain sizes) with a progressive increase in sorting. since hydraulic conductivity increases with increasing grain sizes and sorting, hence, excellent aquifer characteristics for the groundwater within the study area. The foregoing revealed that the aquifer geometry and properties of the study areas is favourable for the availability of drinking water for both the Urban and rural dwellers within these communities. Keywords: Aquifer geometry, groundwater, hydraulic conductivity, Anambra Basin

scholarly journals Granulometric and facies analysis of Middle–Upper Jurassic rocks of Ler Dome, Kachchh, western India: an attempt to reconstruct the depositional environment

Geologos ◽  
2019 ◽  
Vol 25 (1) ◽  
pp. 51-73 ◽  
Author(s):  
Asma A. Ghaznavi ◽  
M.A. Quasim ◽  
A.H.M. Ahmad ◽  
Sumit K. Ghosh
Keyword(s):  
Grain Size ◽  
Facies Analysis ◽  
Upper Jurassic ◽  
Depositional Environments ◽  
Coarse Grained ◽  
Energy Conditions ◽  
Grain Size Analysis ◽  
Size Analysis ◽  
Western India ◽  
Jurassic Rocks

Abstract Grain size analysis is an important sedimentological tool used to unravel hydrodynamic conditions, mode of transportation and deposition of detrital sediments. For the present study, detailed grain size analysis was carried out in order to decipher the palaeodepositional environment of Middle–Upper Jurassic rocks of the Ler Dome (Kachchh, western India), which is further reinforced by facies analysis. Microtextures were identified as grooves, straight steps and V-shaped pits, curved steps and solution pits suggesting the predominance of chemical solution activity. Grain size statistical parameters (Graphic and Moment parameters) were used to document depositional processes, sedimentation mechanisms and conditions of hydrodynamic energy, as well as to discriminate between various depositional environments. The grain size parameters show that most of the sandstones are medium- to coarse-grained, moderately to well sorted, strongly fine skewed to fine skewed and mesokurtic to platykurtic in nature. The abundance of medium- to coarse-grained sandstones indicates fluctuating energy levels of the deposition medium and sediment type of the source area. The bivariate plots show that the samples are mostly grouped, except for some samples that show a scattered trend, which is either due to a mixture of two modes in equal proportion in bimodal sediments or good sorting in unimodal sediments. The linear discriminant function analysis is predominantly indicative of turbidity current deposits under shallow-marine conditions. The C-M plots indicate that the sediments formed mainly by rolling to bottom suspension and rolling condition in a beach subenvironment. Log probability curves show that the mixing between the suspension and saltation populations is related to variable energy conditions.

High-resolution records of grain-size and depositional environment correlated to the Homo erectus Nariokotome Boy site, West Turkana, Kenya

2021 ◽  
Author(s):  
Conner O'Reilly ◽  
Catherine C. Beck ◽  
Jeroen H. van der Lubbe ◽  
Craig S. Feibel ◽  
Bruce Wegter ◽  
...  
Keyword(s):  
Grain Size ◽  
High Resolution ◽  
Homo Erectus ◽  
Eastern Africa ◽  
Coarse Grained ◽  
Grain Size Analysis ◽  
Size Analysis ◽  
Sedimentary Sequences ◽  
Grain Size Distributions ◽  
Material Grain Size

<p>The Turkana Basin in northern Kenya contains a robust record of hominin fossils, including Nariokotome Boy (discovered from the NK3 site), the most complete H. erectus specimen found to date. Understanding the paleoenvironmental context in which hominins such as H. erectus evolved has been an objective of decades of research in eastern Africa. Here, we present a study using grain size analyses to infer the paleoenvironmental conditions responsible for the deposition of the sedimentary sequences directly associated with NK3. We resampled a ~14 m interval at from the West Turkana Kaitio (WTK13) core, collected as part of the Hominin Sites and Paleolakes Drilling Project. This interval ties directly to the outcrop where Nariokotome Boy was recovered. By sampling continuously at 0.5 cm intervals (~7 yrs/sample), we document the paleoenvironment in ultra high-resolution (i.e. a scale relevant to a hominin life) that directly correlates to the NK3 site. Over 350 sediment samples were pre-treated to remove carbonate, biogenic silica, and other organic material from detrital material. Grain size distributions were measured on a Malvern Mastersizer 3000 using wet suspension. Based on these analyses, the interval was dominated by silt, which was further investigated using end-member modeling. A four end-member solution explained on average 99% of the population variability. The bottom of the interval was more coarse-grained, with an abrupt fining transition at 38.83 meter below surface (mbsf), which corresponds with the transition out of a tuffaceous interval (Natoo tuff) and into a pedogenically modified interval. This correlation is significant as the top of this tuff is the surface upon which Nariokotome Boy was recovered. Previous facies and grain size analyses revealed and quantified Turkana’s dynamic lake level history. However, our grain size analysis provides unprecedented resolution for the paleoenvironment during which Nariokotome Boy lived. Our 0.5 cm sampling resolution enables us to quantify depositional changes on a scale comparable with previous descriptive facies analyses and to refine transitions between paleosols, fluvial deposits, and lacustrine deposition at the interface of these three paleoenvironments enabling us to reconstruct a dynamic lakeshore environment during the lifetime of the Nariokotome Boy.</p>

scholarly journals Comparison of hydraulic conductivities by grain-size analysis, pumping, and slug tests in Quaternary gravels, NE Slovenia

2015 ◽  
Vol 7 (1) ◽  
Author(s):  
Tatjana Pucko ◽  
Timotej Verbovšek
Keyword(s):  
Grain Size ◽  
Correlation Coefficients ◽  
Pumping Test ◽  
Test Method ◽  
Coarse Grained ◽  
Grain Size Analysis ◽  
Small Radius ◽  
Size Analysis ◽  
Pumping Tests ◽  
Slug Tests

AbstractHydraulic conductivities (K) can be obtained from pumping and slug tests as well as grain size analysis. Although empirical methods for such estimations are longstanding, there is still insufficient comparison of K values among the various approaches. Six grain-size analysis methods were tested on coarse-grained alluvial sediments from 12 water wells in NE Slovenia. Values of K from grainsize methods were compared to those of pumping tests and slug tests. Six grain-size methods (USBR, Slichter, Hazen, Beyer, Kozeny-Carman, and Terzaghi) were used for comparison with the Theis and Neuman pumping test method and the Bouwer-Rice method for slug tests. The results show that the USBR (US Bureau of Reclamation) method overestimates K values and there is no correlation with other results, so its use is not advised. Conversely, whilst the Slichter method gives much lower estimates of K, it is the only one to completely fulfill the grain size requirements. Other methods (Hazen, Beyer, Kozeny- Carman, and Terzaghi) result in intermediate values and are similar to the Slichter method; however they should be used for smaller-sized sediments. Due to their high transmissivity and small radius of inffiuence, slug tests should be avoided in the analysis of gravels, as they only test a small portion of the aquifer compared to pumping tests. This is confirmed by the low correlation coefficients between hydraulic conductivities obtained from pumping tests and slug tests.

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