CLAY MINERALOGY AND DIAGENESIS OF K-BENTONITES OCCURRING IN THE DEVONIAN YILANLI FORMATION FROM NORTH WESTERN ANATOLIA (BARTIN-ZONGULDAK) &Uuml / nl&uuml / ce, &Ouml / zge M. Sc., Department of Geological Engineering Supervisor: Prof. Dr. Asuman G&uuml / nal T&uuml / rkmenoglu January 2013, 80 pages Yellowish brown and gray-green colored K-bentonite horizons revealing thicknesses up to 60 cm are exposed within the limestone-dolomitic limestone successions (Middle Devonian-Lower Carboniferous Yilanli formation) deposited on a shallow marine carbonate platform at Zonguldak and Bartin area in the western Black Sea region. In this study, bentonite samples collected from two different locations / Gavurpinari quarry and Yilanli Burnu quarry are investigated by means of optical microscopy, X-ray powder diffraction analyses (XRD), both scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis, high resolution transmission electron microscopy (HR-TEM) and inductively coupled plasma mass spectrometry (ICP-MS) in order to reveal their mineralogicalgeochemical characteristics and understand their origin and evolution. Illite is determined as the major phyllosilicate mineral in K-bentonites. Additionally, kaolinite and illite-smectite mixed-layer clay minerals are also detected in some samples. As non-clay minerals calcite, dolomite, quartz, gypsum, feldspar, pyrite and zircon are present in these K-bentonites. Crystal-chemical characteristics (K&uuml / bler index-KI, intensity ratios (Ir), illite polytypes (%2M1), (d060) of illite minerals from the two different sampling locations were investigated. Their KI values (for Yilanli Burnu sampling location varying between 0.47-0.93 (with an average of 0.71 &Delta / &deg / 2&theta / ) / for Gavurpinari quarry sampling location varying between 0.69-0.77 (with an average of 0.72 &Delta / &deg / 2&theta / )) / % of swelling component (smectite-max 5%) and crystallite thickness (N=10-20 nm) indicate that these illites were affected by high-grade diagenetic conditions. Similarly, illite polytype ratios (%2M1/(2M1+1Md)) range between 20-50% (with an average of 36%) for the Yilanli Burnu quarry samples, whereas, these ratios are between 25-45% (with an average of 37%) for the Gavurpinari limestone quarry samples. Illite polytpe data also supports a high-grade diagenetic origin possibility of K-bentonites. Illite d060 values ranges between 1.491-1.503 &Aring / , (with an average of 1.499 &Aring / ) which reflect the octahedral Mg+Fe compositions are varying between 0.27-0.51 and thus approach the ideal muscovite-phengite values close to dioctahedral muscovite composition. Based on the data obtained from this study, volcanic ash was firstly transformed into a smectitic I/S mineral in early stages of sedimentation and burial diagenesis. This initial smectite was then be transformed into a highly illitic I/S, and finally illite by diffusion of elements into and out of the bed, during Devonian. Mineralogical-petrographical data points out that these K-bentonites evolved in a high-grade diagenetic environment (approximately 100-150 &deg / C) from the products of volcanic eruptions having yet unknown source and distance during Middle-Late Devonian time.

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No description available.

No description available.

An investigation of shale pore structure and compositional/geochemical heterogeneities has been undertaken to elucidate the controls upon gas capacities of potential shale gas reservoirs in northeastern British Columbia, western Canada. Methane sorption isotherms, pore structure and surface area data indicate a complex interrelationship of total organic carbon (TOC) content, mineral matter and thermal maturity affect gas sorption characteristics of Devonian-€”Mississippian (D-€”M) and Jurassic strata. Methane and carbon dioxide sorption capacities of D-€”M shales increase with TOC content, due to the microporous nature of the organic matter. Clay mineral phases arealso capable of sorbing gas to their internal structure; hence D-€”M shales which are both TOC- and clay-rich have the largest micropore volumes and sorption capacities on a dry basis. Jurassic shales, which are invariably less thermally mature than D-€”M shales, do not have micropore volumes which correlate with TOC. The covariance of methane sorption capacity with TOC, independent of micropore volume, indicates a solute gas contribution (within matrix bituminite) to the total gas capacity. On a wt% TOC basis, D-M shales sorb more gas than Jurassic shales: a result of thermal-maturation induced, structural transformation of the D-€”M organic fraction. Organic-rich D-€”M strata are considered to be excellent candidates for gas shales in Western Canada. These strata have TOC contents ranging between 1-5.7 wt%, thermal maturities into the dry-gas region, and thicknesses in places of over 1000 m. Total gas capacity estimates range between 60 and 600 bcf/section where a substantial percentage of the gas capacity is free gas, due to high reservoir temperatures and pressures. Inorganic material influences modal pore size, total porosity and sorption characteristics of D-M shales. Carbonate-rich samples often have lower organic carbon contents (oxic deposition) and porosity, hence potentially lower sorbed and free-gas capacities. Highly mature Devonian shales are both silica and TOC-rich (up to 85% quartz and 5 wt% TOC) and as such, deemed excellent potential shale gas reservoirs because they are both brittle (fracable), and gas-charged. However, quartz-rich Devonian shales display tight-rock characteristics, with poorly developed fabric, small median pore diameters and low permeabilities. Hence potential `frac-zones' will require an increased density of hydraulic fracture networks for optimum gas production.

The Late Devonian was a significant period in Phanerozoic reef evolution. Reef complexes reached their acme in the Middle Devonian and then declined in numbers and complexity thereafter. This change was accompanied by a shift in reef composition characterized by an increase in calcified microbes in the reef milieu. Late Devonian Nisku Formation reefs in the Cynthia Basin at Meekwap, Alberta are composed of calcimicrobes (Renalcis, Epiphyton, Girvanella, Rothpletzella, and Wetheredella), stromatoporoids, and corals. Accessory organisms include brachiopods, benthic foraminifera, molluscs, sponges, bryozoans, and crinoids. Calcimicrobes generate dorsal or ventral crusts on stromatoporoids, and form oncolites in open marine facies. Dorsal crusts are either Girvanella and Rothpletzella, or non-calcimicrobial, spongiostromate or cemented calcisilt encrustations. Ventral crusts are cryptic and composed of Renalcis and Epiphyton. Oncolites comprise layers of Girvanella and Rothpletzella and occur in lagoon and upper-foreslope facies. Girvanella and Rothpletzella are thought to have been photosynthetic because of their preference for interpreted well-lit settings (oncolites and dorsal surfaces) and possible competition for light as expressed by alternating layers of Girvanella and Rothpletzella as well as domal, accretionary growths of either Girvanella or Rothpletzella in oncolites. Renalcis and Epiphyton are viewed as non-photosynthetic or light sensitive because they are rare on upper surfaces and are instead found in cryptic environments. The abundance of calcimicrobes in Meekwap limestones is interpreted to have reflected elevated nutrient levels. Nutrients were likely terrestrially sourced and brought onto the shelf via fluvial runoff and submarine groundwater discharge. Geometry of the Cynthia Basin, as well as the presence of local nutrient sources at Meekwap is thought to have enhanced more regional nutrification via ocean upwelling. The change in the composition of reefs throughout the Late Devonian is attributed to paleoenvironmental changes, such as a colder climate and falling ocean temperatures, as well as increasing nutrient levels, prior to the Late Devonian mass extinction. / Thesis (Master, Geological Sciences & Geological Engineering) -- Queen's University, 2010-12-21 12:24:17.569

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No description available.

The Cleveland Shale displays a characteristic and distinctive pattern of promontories and recessed intervals on weathered outcrops, which appears to represent cyclicity. This weathering pattern can be observed in other shales, both within and outside the Appalachian Basin; so determining the nature of these cycles may be critical for understanding the origin of, not only the Cleveland Shale, but also of black shales in general. Cyclicity in the Cleveland was examined on a decimeter-to-meter scale using lithologic characterization, gamma-ray stratigraphy and x-ray fluorescence, and on a millimeter-to-centimeter scale using organic petrography. Lithologic characterization and gamma-ray stratigraphy revealed Milankovitch-band fourth- and fifth-order cyclicity related to changes in the earth’s orbital eccentricity (100 ka) and obliquity of the earth’s axis (42 ka), respectively. Sedimentological changes associated with these cycles were identified through organic petrography and x-ray fluorescence. A depositional model was developed from these data sets, which suggests that cyclic changes in local climate — from cold and wet to warm and dry — controlled advancing and retreating glaciation in the adjacent Acadian mountains as well as concomitant sea-level rise and fall in the Black-Shale Sea. Such changes would have controlled sediment influx to the sea and are thought to be reflected in the cycles.

The Middle Devonian formations to be studied in this paper are the Jeffersonville and North Vernon Limestones. Together these formations make up the Muscatatuck Group in the Illinois Basin portion of Indiana. In the area of study, the Jeffersonville Limestone consists from the base upwards of the Geneva Dolomite Member, Vernon Fork Member, and Paraspirifer acuminatus Zone. The North Vernon Limestone consists of the Speed Member overlain by the Beechwood Member.In the study area, the subsurface Muscatatuck Group dips to the southwest at a rate of 20 to 50 feet per mile. These rocks thicken to the southwest, and range in thickness from 136 to 170 feet. Closed-structural highs are present on the top of the Muscatatuck Group over Silurian pinnacle-like reefs.Resistivity log - sonic log cross plots were constructed to analyze the subsurface carbonate facies in the study area. A total of 13 cross plots were constructed with over 1,490 points plotted.From this study five conclusions can be drawn about the application and usefulness of the cross plot method in analyzing the the surface distribution of carbonate facies. As explained in the text, these conclusions remain valid only when applied to the area of study.The conclusions are as follows:1. The positioning of the point groups on the cross plots is controlled by the amount and type of porosity present in the rocks.2. Due to the diagenetic alteration of the primary porosity in the rocks, the point groups can not be divided into depositional textures or facies.3. In this case, because of the uncomplex nature of the stratigraphy and the ease of correlation of the lithologic units on the logs, the cross plots were not useful in analyzing the subsurface distribution of the carbonate facies in the area.4. The cross plots were useful in checking the accuracy of the log correlations.5. The cross plots may be used to infer lateral porosity changes in the rock units, and possibly variations in the diagenetic alteration within these units.