Incident Light Microscopy Research Articles

Mineralogy and Geochemistry of Rare Earth Elements in Carboniferous-Permian Coals at the Eastern Margin of the Ordos Basin.

This article used Carboniferous-Permian coals from the Jungar, Hedong, and Weibei Coalfields in the east of the Ordos Basin as research samples. Characteristics of coal quality, petrology, mineralogy, and geochemistry were analyzed by proximate analysis, inductively coupled plasma mass spectrometry, X-ray fluorescence spectroscopy, X-ray diffraction analysis, scanning electron microscopy-energy spectrum analysis, and incident light microscope. The enrichment regulations, distribution patterns, and occurrences of REY (rare earth element and yttrium) in coal under different geological conditions were compared. Geological significance and the influence of REY were then discussed. The average REY of Permian coal in the eastern margin of the basin is 127.9 μg/g, CC = 1.87, and the average REY of Carboniferous coal is 117.49 μg/g, CC = 1.72, which are within the normal enrichment range. The inorganic affinity of REYs in the study area is strong and mainly occurs in clay minerals and detrital phosphates and correlates well with LREY. The Permian coal sedimentary environment is more oxidized than the Taiyuan formation, and the Carboniferous coal sedimentary environment is noticeably more affected by marine water. With an increasing degree of coalification, the concentration of rare earth elements (REE) in high-rank coal vitrinite is lower than that in inertinite. In contrast, the concentration of REEs in low-rank coal is the opposite. This is because the oxygen-containing functional groups that can combine with REEs in vitrinite reduce significantly, resulting in the loss of trace elements into other forms. The provenance of the northern and central regions of the study area is mainly sedimentary rocks, granite, alkaline basalt, and continental tholeiite, while the southern region is mainly granite and sedimentary rocks.

High‐Temperature Fracture Growth by Constrained Sintering of Jadeite and Quartz Aggregates

AbstractFractures control heat and mass transfer and rheology in a wide range of subsurface regimes, ranging from low‐temperature diagenetic environments to high‐temperature metamorphic and magmatic systems. To investigate processes of opening‐mode fracture growth at high homologous temperature, we conducted constrained high‐temperature sintering experiments of thin layers of porous jadeite and quartz aggregate attached to a non‐sintering mullite substrate. Samples were heated stepwise at a low rate in a muffle furnace from 25°C to 1,000°C under ambient air pressure and examined for changes in mineral composition, texture, porosity, and fracture morphology using powder‐X‐ray diffraction, macro‐photography, reflected incident light microscopy, and secondary electron microscopy. Mineral reactions in the jadeite and quartz sample layer include jadeite and quartz reacting to albite at 600°C and the formation of nepheline and orthoclase at 900°C and 1,000°C. Opening‐mode fractures are first observed at 850°C coincident with the first presence of a melt phase with low aperture‐to‐length ratios similar to elastic‐brittle fractures. At 900°C, melt becomes increasingly abundant, and fractures obtain ductile morphology with high aperture‐to length ratios and blunted tips resulting from fracture growth by growth and coalescence of larger pores at the expense of smaller pores. In the absence of an externally applied mechanical load, we conclude that fracture growth is driven primarily by sintering stress resulting from differential contraction between sample layer and substrate associated with high‐temperature mineral reactions, melt formation and redistribution, and changes in pore structure. Similar fracture processes may be relevant to the segregation and migration of melt in magmatic systems.

Organic petrology of Ora formation in Akkas field, western Iraq

Detailed petrological investigation of the organic matter has been performed using polished sections examined under incident light microscopy on the Lower Carboniferous Ora formation in Akkas field to characterize the nature and origin of the contained organic matter in the shale beds. Microscopical investigations reveal that the organic matter consists of mixed terrestrial and marine organic matter. Marine organic matter represented by alginite and bituminte; whereas terrestrial is represented predominantly by sporinite, and minor amounts of vitrinite.

Geochemical Evaluation and Pore Type Characterization of Carbonaceous Rich Facies in Brown Shale Formation, Central Sumatra Basin

DOI:10.17014/ijog.7.2.121-133Brown Shale Formation of Pematang Group is a key source rock in the Central Sumatra Basin. The formation consists of three lithofacies: algal rich facies, mixed algal-carbonaceous facies, and carbonaceous rich facies. This paper focuses on evaluating the geochemistry and on characterizing the porosity of the carbonaceous rich facies. Geochemical evaluation of the carbonaceous source rocks was conducted using Rock-Eval pyrolysis, while mineralogy and microtextural characterization were assessed by incident light microscopy and scanning electron microscopy (SEM). The results show that the organic components of the carbonaceous source rocks are predominantly composed of vitrinite with minor inertinite and liptinite. The geochemical characteristics indicate that the carbonaceous rich facies could be ranked as a good to excellent level in terms of source rock potential with high TOC content, mainly containing kerogen type III as a gas prone potential. SEM results show that the pore types in the carbonaceous source rocks can be classified into three main types: porous floccules, organic-porosity, and intraparticle pores. Thus, the carbonaceous rich facies of the Brown Shale Formation contains gas prone source rocks with good generation potential, as well as organic rich shale unconventional reservoirs.

Analysis of air voids in cementitious materials using micro X-ray computed tomography (µXCT)

Air void parameters in cementitious materials are usually identified and analysed manually using image techniques such as incident light microscopy (ILM). The investigative procedure requires considerable effort, and the analysis results can vary between operators. This article presents an approach to the analysis of air void parameters (air void distribution, total and micro air void occurrence, specific surface and spacing/distance factor) in mortars and concretes by using micro X-ray computed tomography (µXCT). By taking the difference in circularity of circle-similar voxel clusters into account, air voids can be distinguished from other pores or cracks with the help of a specialised algorithm. The article gives some recommendations on how the speed and quality of the measurements can be improved by means of refinements in measurement settings and sample preparation. Finally, an approach for determining the threshold (image analysis), which has a significant influence on the results, is presented. A comparison between results from µXCT and ILM make the potential application of this method for determining air void parameters in accordance with EN 480-11 clear.

Membrane scaling in Vacuum Membrane Distillation - Part 1: In-situ observation of crystal growth and membrane wetting

This paper presents an experimental approach to investigating scale formation in Vacuum Membrane Distillation using in-situ optical crystal growth tracking and synchronized identification of membrane wetting. An incident light microscopy setup was used to monitor crystal growth on the membrane in the feed channel. An image processing strategy called Digitally Simulated Dark Field Illumination helped overcome the extremely low contrast between translucent crystals and the membrane surface. Further image processing and statistical evaluation enabled us to quantitatively track the population of crystals on the membrane. Simultaneously, membrane wetting was monitored using tracer-based Laser Induced Fluorescence. This allowed us to locate membrane leakages. The combination of these two experimental techniques gave insight into the coupling mechanisms of scaling and membrane wetting in Vacuum Membrane Distillation, where classical methods for wetting detection could not be applied. The methodology was tested with different scalants under process conditions to rate its performance and identify limitations.

Variation in facial bone growth remodeling in prehistoric populations from southern South America.

To assess the intraspecific variation in bone remodeling patterns in modern humans, we studied two populations from southern South America that represent the extremes of morphological variation in this region. We particularly analyzed the ontogenetic changes in the patterns of bone growth remodeling and compared the patterns between samples. We obtained high-resolution casts of the periosteal surface of the upper and middle face of subadults (n = 36) and adult (n = 36) individuals from a sample of hunter-gatherers from Patagonia and a sample of horticulturists from Northwest Argentina. The areas of bone formation and resorption were registered using an incident-light microscope. We then estimated the average bone remodeling map by sample and age, and performed principal component analysis and multivariate regressions to assess the extension and distribution of these areas across ontogeny and between samples. We found that the remodeling pattern of the glabella, supraorbital arch, frontal process of the maxilla, and a large part of the zygomatic bone is relatively constant in subadults and adults from both sample with a clear predominance of bone formation. In contrast, the middle face is characterized by the spatial alternation between formation and resorption areas, and greater variation with age and between samples. The main differences were found in areas related to chewing and muscle insertions. Our study provides the first evidence of interpopulation variation in bone growth remodeling and suggests that biomechanical factors can influence the observed patterns. It also underlines the need to account for ecological factors in within and between species comparisons.

In-situ analyses of carbonaceous matter in manganiferous black shales: Analytical proxies and implication for ore processing

Carbonaceous matter is generally known to be problematic for metal recovery during metallurgical processing of black shales. In particularly, metal upgrading during beneficiation prior to (bio-) hydrometallurgical and/or pyrometallurgical processing is hindered by the presence of abundant carbonaceous matter (CM). This study presents the characterization of CM and mineral bound carbonaceous matter (CMP) in three manganese carbonate-rich shales hosting 6–8 wt% total organic carbon. Non-destructive methods, such as incident light microscopy, scanning electron (SEM) and focused-ion-beam-transmission electron microscopy (FIB-TEM), QEMSCAN and electron microprobe, were used to show that free CM is adsorbed onto illite-smectite surfaces. This form of CM ranges in grain size from sub-micrometer up to ≈100 μm. The most efficient method to show the illite-smectite association is SEM and for quantification of this association, QEMSCAN should be used. Mineral-bound carbonaceous matter may be relicts of extrapolymers (pyrite and/or carbonate) and needs characterization using FIB-TEM. The quantity of CM can then be estimated by a rough calculation as the difference between the total organic carbon (Rock Eval) and the free carbon calculated from normative mineral compositions based on X-ray Fluorescence (XRF) and X-ray-Diffraction (XRD) analyses. The mineral bound CM could not be detected by QEMSCAN under conventional analytical conditions. We estimated that about 85% of the CM in the test samples was adsorbed on mineral surfaces and about 15% was bound to minerals. The physical protection of the CM by clays, and the morphological and density differences between pyrite, carbonates and biochemically-bound CM in pyrite/carbonates needs to be taken into consideration in the process design.

How Hedstrom files fail during clinical use? A retrieval study based on SEM, optical microscopy and micro-XCT analysis.

This study was conducted to evaluate the failure mechanism of clinically failed Hedstrom (H)-files. Discarded H-files (n=160) from #8 to #40 ISO sizes were collected from different dental clinics. Retrieved files were classified according to their macroscopic appearance and they were investigated under scanning electron microscopy (SEM) and X-ray micro-computed tomography (mXCT). Then the files were embedded in resin along their longitudinal axis and after metallographic grinding and polishing, studied under an incident light microscope. The macroscopic evaluation showed that small ISO sizes (#08-#15) failed by extensive plastic deformation, while larger sizes (≥#20) tended to fracture. Light microscopy and mXCT results coincided showing that unused and plastically deformed files were free of internal defects, while fractured files demonstrate the presence of intense cracking in the flute region. SEM analysis revealed the presence of striations attributed to the fatigue mechanism. Secondary cracks were also identified by optical microscopy and their distribution was correlated to fatigue under bending loading. Experimental results demonstrated that while overloading of cutting instruments is the predominating failure mechanism of small file sizes (#08-#15), fatigue should be considered the fracture mechanism for larger sizes (≥#20).

Extracellular ice management in the frost hardy horsetail Equisetum hyemale L.

Formation of extracellular ice at specific positions in the plant interior is a common and probably essential component of plant cold hardiness. Studies on extracellular freezing in spore-bearing plants are, however, scarce. In this study, extracellular ice formation in the cold hardy horsetail Equisetum hyemale L. is analyzed. Horsetails show an extensive system of intercellular air spaces which are probably crucial for internal ice storage during winter. Previous studies emphasized the spacious pith cavity as the main place for ice crystal growth. Shoots were studied during summer and in the frozen state in winter, after natural acclimatization, by using digital (incident light) microscopy, Scanning Electron Microscopy and Cryo Scanning Electron Microscopy. It was shown that the vallecular canals also contain a large share of ice bodies under freezing conditions. The vallecular canals, which are directly seated within the cortex and whose interior is directly connected to the cortex via gaps in the canal wall, were often and rapidly filled with ice. The pith cavity also contained ice, depending on the position along the shoot and the internode. The carinal canals contained almost no ice crystals. Furthermore, some ice crystals were detected in the intercellular spaces of the chlorenchyma and the substomatal chamber. The stomatal antechamber, however, was always ice-free, probably due to the presence of water-repellent wax crystals. The results of this study support available evidence for the crucial role of pre-existing extensive lacunae for extracellular ice formation in E. hyemale. Furthermore, the findings indicate that anatomical details of canal structure and position are important for the pattern of extracellular ice accumulation.

A Multi-instrument Study of Microwear Polishes on Mousterian Tools from Weasel Cave (Myshtulagty Lagat), Russia

ABSTRACTThe functions of flaked stone tools are usually determined by the observation of microwear polishes with the incident-light microscope with magnifications of 50–400× – known as the Keeley Method. In our study into the function of Mousterian flint tools from Weasel Cave, we employ the atomic force microscope (AFM) and the optical interferometer, in addition to the light microscope and the SEM. The advantage of the AFM and the interferometer are the extremely high resolution permitted and most importantly the quantitative data extracted from microwear polishes. The merits of these different instruments are discussed in the context of polish differentiation for microwear traces on archaeological specimens interpreted as due to contact with meat, fresh hide, dry hide, bone, wood, as well as hafting. A multi-instrument approach contributes to the understanding of the formation of microwear polishes as well.

Solid bitumen, bituminite and thermal maturity of the Upper Jurassic-Lower Cretaceous Chia Gara Formation, Kirkuk Oil Field, Zagros Fold Belt, Kurdistan, Iraq

The Upper Jurassic-Lower Cretaceous Chia Gara Formation, a proven marine source rock characterised by predominance of amorphous organic matter (AOM) is known from few outcrops in NE Iraq and a number of exploration wells in the Zagros Fold Belt. This study presents comprehensive organic petrographic and mineralogical investigations of the dispersed organic matter and rock-forming minerals of the Tithonian-Berriasian Chia Gara Formation intersected by the Kirkuk well K-109 drilled in the giant Kirkuk oil field, NE Iraq. The organic petrographic analyses, including incident light microscopy and confocal laser-scanning microscopy (CLSM) were applied to carbonate source rocks with low to moderate organic carbon contents. Our data demonstrate the predominance of bituminite and solid bitumen among the examined dispersed organic matter followed by oil exudates and oil globule inclusions as well as the presence of minor contributions of alginite (i.e., Tasmanites and Leiospheridia), liptodetrinite and vitrinite. Based on optical characteristics and CLSM spectral fluorescence measurements, examinations of bituminite point towards the presence of bituminite type III. The bituminite type III encloses dark orange fluorescent amorphous components suggesting a genetic relationship either with liptodetrinite and/or with solid bitumen. The qualitative assessment of solid bitumen reveals several dissimilar forms identified in the analysed samples. The photometric and spectral fluorescence measurements point to distinct reflectance values ranging between 0.19% and 0.43% SBRr and lambda max values extending from 515nm to 590nm, respectively. The corresponding results of the solid bitumen exhibit (1) a lack of a relationship with depth and, (2) suggest its poor property as a reliable maturity indicator for the examined samples. The presence of oil exudates, oil globule inclusions and their association with solid bitumen suggests a genetic relation with the examined residues of liquid hydrocarbon phase. The performed thermal maturities assessments of dispersed organic matter point towards early-mature to peak-mature oil window with vitrinite reflectance values ranging between 0.52% VRr at 2801m to 0.83% VRr at 3089m depth. Mineralogical analyses revealed the predominance of calcite over dolomite in the examined limestone to marl lithofacies (e.g., clear rimmed dolomite) with localised intensive dolomitisation. In the phyllosilicate-rich matrix, predominance of calcite and siderite is observed, followed by zinc blende and pyrite. The composition of organic matter in the examined Chia Gara Formation with predominance of bituminite and solid bitumen makes the major marine source rock of Iraq's Cretaceous petroleum systems distinctive in terms of hydrocarbon generation and migration at an oil window stage as it provides suitable explanations for its generally low hydrogen index (HI) with only minor terrestrial input. In addition, the results presented herein can be helpful for future evaluation of thermal maturities and characterisation of optical appearances of dispersed organic matter in carbonates by incident light microscopy and especially by CLSM during hydrocarbon prospecting.

ERROR INTRAOBSERVADOR EN EL ANÁLISIS PALEOHISTOLÓGICO DE SUPERFICIES CRANEOFACIALES

Fil: Brachetta Aporta, Natalia. Universidad Nacional de La Plata. Facultad de Cienicas Naturales y Museo. Division Antropologia; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas; Argentina

Evaluation of microleakage in class V composite restorations using dye penetration and micro-CT.

The aim of this study was the evaluation of microleakage in class V cavities using micro-CT imaging and dye penetration. Sixty class V cavities were prepared, randomly divided into five groups (Adper Single Bond Plus (ASB), ExciTE (EX), iBond TE (ITE), Optibond Solo Plus (OSP), Prime & Bond NT (PB)) and restored with Venus Diamond. After thermocycling and dye penetration test with 50wt% ammoniacal silver nitrate, eight samples per group were sectioned longitudinally and evaluated under a coaxial incident light microscope (enamel (E) and dentin (D) measurement in mm). The remaining samples were analyzed by counting voids in the coronal and cervical adhesive areas by means of micro-CT. In dentin, no statistically significant difference in dye penetration was found. In enamel, OSP showed significant higher microleakage than all other adhesives (p<0.001). Groups ITE, ASB, PB, and EX showed a significantly lower penetration depth in E than in D (p<0.001). The results of the micro-CT examination in dentin are contrary to the findings of the microleakage evaluation. Regarding enamel, only group PB showed significant more voids than EX in enamel (p<0.02). Within the adhesive groups, PB showed significantly more voids in E than in D (p<0.04). This test method must be optimized by developing a new leakage tracer for a better differentiation between hard tissues and dental materials. The micro-CT is not yet a vulnerable tool to evaluate the marginal integrity of resin composites.

Application of confocal laser-scanning microscopy (CLSM) to autofluorescent organic and mineral matter in peat, coals and siliciclastic sedimentary rocks — A qualitative approach

Organic matter occurring in the form of macerals and natural solid bitumens in peats, coals, and siliciclastic sediments of various stratigraphic ages and locations was studied by means of conventional incident light microscopy and CLSM. Classical optical microscopic investigations are restricted by conventional 2-D imaging and are often hindered by the associated out-of-focus-blur effects. The qualitative application of CLSM overcomes these limitations, permitting to reveal precisely 3-D morphology and detailed microstructure of autofluorescent organic matter. The in depth examinations along Z-axis in XY, XZ, or YZ scanning modes at increments of 250nm are capable to reconstruct 3-D internal configuration and arrangement occurring in autofluorescent macerals. The non-invasive and non-destructive laser-raster technique is applied to characterize in situ autofluorescent organic particles at micron to sub-micron scale resolution in polished whole rock pellets. In this study, we demonstrate that CLSM is suitable to (i) detect fine-scale microstructure of autofluorescent organic matter, (iii) reconstruct 3-D morphology at cellular and tissue level, (iii) analyze maceral composition in terms of its relicts and fragments beyond the classical optical assignment limits, (iv) detect and examine inorganic components enclosed in the embedding mineral-bituminous groundmass, and (v) differentiate mineral constituents from the remaining organic matter.CLSM as an optical microscopic technique was applied to generate high-resolution 2-D and 3-D images, projections as well as 3-D reconstructions of autofluorescent objects excited with aid of laser-induced light operating at variable visible wavelengths. CLSM is applicable to support microscopic studies of thermally immature and mature organic matter within the oil and early gas windows enclosed either within siliciclastic and carbonate sediments or in peat and low to medium rank coals.The application of this technique will be of great interest to a wide range of geology related disciplines such as petroleum geology, biostratigraphy, marine geology, peat petrography, and archeology.

Standardised classification of pre-release development in male-brooding pipefish, seahorses, and seadragons (Family Syngnathidae)

BackgroundMembers of the family Syngnathidae share a unique reproductive mode termed male pregnancy. Males carry eggs in specialised brooding structures for several weeks and release free-swimming offspring. Here we describe a systematic investigation of pre-release development in syngnathid fishes, reviewing available data for 17 species distributed across the family. This work is complemented by in-depth examinations of the straight-nosed pipefish Nerophis ophidion, the black-striped pipefish Syngnathus abaster, and the potbellied seahorse Hippocampus abdominalis.ResultsWe propose a standardised classification of early syngnathid development that extends from the activation of the egg to the release of newborn. The classification consists of four developmental periods – early embryogenesis, eye development, snout formation, and juvenile – which are further divided into 11 stages. Stages are characterised by morphological traits that are easily visible in live and preserved specimens using incident-light microscopy.ConclusionsOur classification is derived from examinations of species representing the full range of brooding-structure complexity found in the Syngnathidae, including tail-brooding as well as trunk-brooding species, which represent independent evolutionary lineages. We chose conspicuous common traits as diagnostic features of stages to allow for rapid and consistent staging of embryos and larvae across the entire family. In view of the growing interest in the biology of the Syngnathidae, we believe that the classification proposed here will prove useful for a wide range of studies on the unique reproductive biology of these male-brooding fish.

Atomic force microscopy of microwear traces on Mousterian tools from Myshtylagty Lagat (Weasel Cave), Russia

Since durable technology emerged between 3.4 and 3.2 million years ago, stone tools served as a major material means that hominins used to survive. Determining how different lithic tools functioned is a principal question in human evolution. The main experimentally based approach to the functional study of lithic technology uses stereo and incident-light microscopy, and is known as the Keeley Method. Although this method has demonstrated success in linking the morphology of microwear traces on flint tools to the function of the tool, there is no agreed upon model of how these microwear polishes form. At the same time, the characterization of these polishes has been a largely qualitative process. Herein, we use the atomic force microscope (AFM) to scan microwear traces on Middle Palaeolithic (Mousterian) tools from Weasel Cave, Russia to show quantitative data and small scale features of microwear polishes interpreted (using the Keeley Method) as due to contact with meat, fresh hide, dry hide, bone, wood, and hafting. These results follow those of to the previous AFM study on the experimental tools, namely that the meat and dry hide polishes are the least developed polishes with smaller changes in roughness and that the bone polish and wood polishes are more highly developed polishes and exhibit larger changes in roughness.

Pits with coloured halos formed on 1Cr18Ni9Ti stainless steel surface after ennoblement in seawater

Micropits surrounded by coloured halos were observed under incident-light microscope on 1Cr18Ni9Ti stainless steel surface after “ennoblemen t” in seawater. Ennoblement has been attributed to biofilm formation on stainless steel surface in seawater. In this study, the environment in biofilm for ennoblement was simulated by adding H 2O 2 into seawater at concentrations that were reported to detect in marine biofilm [N. Washizu, Y. Katada, T. Kodama, Corros. Sci .46 (2004)1291.]. H 2O 2 increased the passivity of stainless steel in seawater, but this passivation was not uniform. The probability of pitting corrosion was increased after ennoblement. Equal thickness interference on the deposition film around the pits was believed to be the reason for the coloured fringes. It is conceivable that haloed pits on the stainless steel surface are the characteristic morphological indications for pitting corrosion formed under ennoblement condition in seawater. Examinations on the microbial and structural effects of the biofilm were not included in this study.

Transverse Compression Behavior of Softwood and Alternately Laminated Lumber of Rubberwood Veneer and Falcata Veneer

Softwood and alternately laminated lumber of rubber wood veneer and falcate veneer were compressed transversely. On the assumption that softwood and alternately laminated lumber are recognized as laminated composite structure of soft layer and hard layer, transverse compression strength of them are expected to be larger than that of lumber only of weaker layer (earlywood and falcate veneer). Cross section of transversely compressed softwood was observed using digital image correlation for strain analysis, and large shear strain has progressed on earlywood at edge of the softwood specimen. The cross section of the specimen after compression was examined under an incident-light microscope, so it was found that compression crush lines began on the boundary between earlywood and latewood at the edge of the specimen. It is probably because of shear stress generated at the boundary between soft layer and hard layer, that is, latewood of high-density would prevent earlywood of low-density from deforming under compression stress. However, when alternately laminated lumbers which are a similar structure to softwood were compressed transversely, shear strain was found not at the edge but at the inner part of the specimen. Moreover compression strength of alternately laminated lumber has been no larger than laminate lumber of falcate veneer. The area of large shear strain has formed inclined lines on the laminated lumber under compression stress, and the lines tended to coincident with checks formed by rotary peeling using a lathe. The lathe checks would mitigate the restriction of hard layer (rubber wood veneer), and so the alternately laminated lumber may not behave similar to softwood.

Paleoenvironments, organic petrology and Rock-Eval studies on source rock facies of the Lower Maastrichtian Patti Formation, southern Bida Basin, Nigeria

The southern Bida Basin in central Nigeria forms a part of the larger Bida or Middle Niger Basin, which is contiguous with the south east trending (petroliferous) Anambra Basin. These basins were major depocenters for Campanian–Maastrichtian sediments in southern and central Nigeria prior to the build up of the Tertiary Niger delta. The successions in the southern Bida Basin consist of the basal Lokoja Formation, overlain by the Patti Formation and capped by the Agbaja Formation. The Lokoja Formation is a sequence of matrix supported conglomerates and sandstones overlying the Pre-Cambrian to Lower Paleozoic basement. Depositional environments are predominantly within fluvial systems of a continental setting. The Patti Formation consists of dark grey carbonaceous shales; mudstone and siltstones representing flood plains to shallow marine deposits with likely organic rich intervals. The overlying Agbaja Formation is made up of ferruginised oolitic and kaolinitic mudstone of a marginal marine environment. Twenty samples of shales of the Patti Formation were studied by incident light microscopy and geochemical analysis to determine the maceral components, geochemical type and potential yield of the pyrolysate. Maceral analysis indicate a large abundance of vitrinite (50–85%; mean = 66%); moderate abundance of liptinites (10–33%; mean = 18%) and lesser amounts of inertinite (9–40%; mean = 16%). Total organic carbon (TOC) values vary from 0.17 to 3.8 wt.% (mean = 2.1 wt.%) with most samples having greater than 2 wt.% TOC. Three of the samples yield greater than 2 kg (HC)/ton of rock suggesting a fair source rock potential. Most of the samples are thermally immature to marginally mature with vitrinite reflectance ranging from 0.4 to 0.6% R om and T max values of 407–426 °C. Given the prevalence of the humic Type III kerogen, maturity and hydrocarbon potential yields, we conclude that the Patti Formation source rock facies have moderate to fair potential for gaseous hydrocarbons which have not yet been generated at the present day outcrop levels but could be important gas source where buried down-dip.