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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. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

This study utilised U-Pb geochronology, and 40Ar/39Ar and (U-Th)/He thermochro-nology to delineate arc magmatism, metamorphism, and exhumation of the pericratonic Yukon-Tanana terrane in the McQuesten map area of west-central Yukon, Canada. SHRIMP U-Pb ages delineate Mid to Late Paleozoic arc magmatism and fit key units into the regional lithotectonic framework of the terrane. The juxtaposition of unmetamorphosed and predomi-nantly undeformed Devono-Mississippian rocks in the northwest of the study area with polydeformed and up to amphibolite facies metamorphosed rocks in the southwest suggests a crustal-scale discontinuity, the Willow Lake fault, bounds the two domains. The asymmetric distribution of 40Ar/39Ar ages across the fault suggest it is extensional, and was active in the Early Jurassic. Zircon (U-Th)/He ages delineate erosion of rocks in the northwest through the upper crust during the Late Triassic and Late Jurassic to Early Cretaceous followed by Mid-dle Cretaceous erosion of the southwestern domain and possibly fault reactivation.

La paléoflore du Jurassique moyen et supérieur du bassin parisien est documentée par un ensemble de gisements assez importants et relativement peu connus, contenant des fossiles de tous types, généralement sous forme d’empreintes avec ou sans cuticule, ou encore sous forme de silicification dans des chailles. Huit gisements historiques ou nouveaux ont été étudiés, plus quatre fossiles isolés, tous datant de l’intervalle Bathonien-Oxfordien, et répartis sur l’ensemble du bassin parisien et de ses marges. Trois gisements ont étés étudiés dans la partie Est du bassin, Il s’agit d’Arc-en-Barrois (Bathonien supérieur), d’Étrochey (Callovien inférieur et moyen) et de Laignes (Callovien moyen). Ils appartiennent tous à l’archipel de la plate-forme bourguignonne, dont les îles étaient alors couvertes d’une forêt mixte xérophytes à Brachyphyllum. Le gisement d’Auxey, situé plus au sud, près de Beaune, daté de l’Oxfordien supérieur, montre au contraire une flore de milieu humide, riche en fougères. Deux autres gisements ont été étudiés au niveau du seuil du Poitou, les flores du Callovien moyen de Sauzé-Vaussais et des environs de Poitiers, riches en bennettitales, correspondant probablement à des milieux xéromorphes assez ouverts. Enfin, deux derniers gisements ont étés étudiés dans l’ouest du bassin, sur la marge orientale du massif armoricain alors émergé, les flores du Bathonien supérieur de Mamers et de Nonant-le-Pin. Ces deux gisements correspondent à des forêts mixtes côtières à Brachyphyllum, dans un milieu également xéromorphe. Ainsi, le bassin parisien présente au Bathonien et au Callovien exclusivement des flores côtières xérophytes, correspondant à des paléoenvironnements plutôt fermés, comme sur la plate-forme bourguignonne, jusqu’à des milieux au contraire assez ouverts, comme dans le Poitou. Les flores de milieu interne, loin des côtes, ne sont pas connues pour cette période. À l’Oxfordien supérieur en revanche, la flore d’Auxey indiquerait plutôt une certaine humidification du climat, bien que de plus amples données soient nécessaires pour confirmer cette interprétation. / The palaeoflora of Late and Middle Jurassic of the Paris basin is documented by a set of rather important outcrops, relatively little know, containing fossils of every type, mainly imprints often without cuticle, sometime with, or otherwise silicification in flint nodules. Eight historic or new outcrops were studied, plus four isolated fossils, all dating from the Bathonian-Oxfordian interval and distributed on the whole Paris basin and its margins. Three deposits were studied in the eastern part of the basin, its Arc-en-Barrois (late Bathonian), Étrochey (early and middle Callovian), and Laignes (middle Callovian). They all belong to the archipelago of the Burgundian platform, whose islands are covered by a mixed xerophytes Brachyphyllum forest. The deposit of Auxey, situated to the south, close to the city of Beaune, dated of late Oxfordian shows on the contrary a flora of wet environments, rich in ferns. Two others outcrops were studied close to the seuil du Poitou, the late Callovian flora of Sauzé-Vaussais and Poitiers surroundings, rich in bennettitales, presumably corresponding to relatively open xeromorphic environments. Finally, two last deposits were studied in the west of the basin, on the oriental margin of the emerged Armorican massif, the flora of the late Bathonian of Mamers and Nonant-le-Pin. These two outcrops correspond to a coastal mixed Brachyphyllum forest, also in a xeromorphic environment. Thereby, the Paris basin presents from Bathonian to Callovian exclusively xerophytes floras, corresponding to rather closed paleoenvironments, as on the Burgundian platform, to on the contrary opened enough environments, as in Poitou. The flora of internal environments, far from coasts, are not known for this period. In late Oxfordian on the other hand, the flora of Auxey would indicate rather a certain moistering of the climate, although more ample data are necessary to confirm this interpretation.

The Jurassic Twist Gulch Formation of central Utah was deposited in the active Arapien sub-basin of the Western Cordillera foreland trough. We herein demonstrate the utility of integrating facies analysis, terrestrial sequence stratigraphy, and detrital zircon (U-Pb) ages to improve paleogeographic reconstructions as well as identify regional unconformities, locate fluvial depocenters, and infer sediment supply/accommodation space ratios. Strata of the Twist Gulch Formation in Pigeon Creek Canyon (PCC) near Levan, Utah consists primarily of alluvial deposits, while in Salina Canyon (SC) the Twist Gulch Formation is comprised of a mix of alluvial and marginal marine deposits associated with the Jurassic Western Interior Seaway. Within the PCC section, a change from high accommodation system (HAS) mudstones to low accommodation system (LAS) multi-storied channel sandstones and back to HAS deposits exists. This same pattern exists in the SC section but culminates with marine deposits. Terrestrial sequence stratigraphy predicts that the change from HAS to LAS deposits indicate a sequence boundary and thus an unconformity. The J-3 unconformity, a regional unconformity on the Colorado Plateau, separates strata of Callovian age from Oxfordian age in Utah. Using detrital zircons (U-Pb), the first radiometric ages were obtained for the Twist Gulch Formation. The J-3 unconformity is bracketed by detrital zircon (U-Pb) ages and stratigraphic relationships in the study area. These new ages suggest that the Twist Gulch Formation is time-equivalent to the Entrada Sandstone, Curtis, and Summerville formations of the Colorado Plateau. Further, integrating facies analysis, terrestrial sequence stratigraphy, and detrital zircon (U-Pb) ages predicts that the PCC section was an active depocenter during the early Oxfordian in which sedimentation outpaced accommodation space, prograding the Oxfordian shoreline of the Jurassic Western Interior Seaway shoreline eastward. This integration process also predicts that subsurface sandstones positioned above the J-3 unconformity on the west side of the Wasatch Plateau are of a different age, depositional system, and systems tract from subsurface sandstones on the east side of the Wasatch Plateau.

<p> Study of the ecology of concretion and host sediment fossils from a shell bed in middle Bajocian clays of northwestern Germany indicates a predominantly epifaunal suspension-feeding community living on a firm mud bottom. The shell bed, firm bottom and low turbidity required by suspension feeders suggests a hiatus or reduced sedimentation at the time. Depth estimates of 50 to 150 m are indicated by ammonite and belemnite siphuncle and septal strength indices.</p> <p> Preservation of calcitic fossils is excellent in both concretions and host sediments. Aragonitic fossils show good preservation in the concretions. Aragonite has been replaced by at least two generations of calcite. Preservation in the host sediments is poor. Pyrite is common in void spaces of concretion fossils but less so in those from the host sediments.</p> <p> Eight concretions were studied, containing numerous Stephanoceras mutabile (macroconch) and Stephanoceras quenstedti (microconch). These are of opposite sexes but are not a dimorphic pair.</p> <p> Distribution of shell debris and other fossils within the concretions suggests that the ammonites were swept by currents into shallow depressions in the sea floor lined with shell debris. Such depressions have been observed in modern sediments as the result of the feeding activity of rays. The presence of currents is indicated by the southwest orientation of belemnite rostra in the host sediments. Carbonate content of concretion matrix is high indicating concretion growth in very fluid muds. This contrast with the firm bottom indicated by fossil ecology suggests rapid burial of the benthic community by either a mudflow or a sudden, large increase in sedimentation. Concretion growth was initiated by decomposition of organic matter within the mud.</p> / Thesis / Master of Science (MSc)

The petrified wood for this study was collected from the Upper Jurassic Morrison Formation in the south central part of Utah on the Colorado Plateau. The study area, located near Clay Point, Garfield County, Utah, is south of the Henry Mountains. The site is relatively undisturbed containing many well preserved specimens. This study constitutes the first detailed study of fossil coniferous woods of the Morrison Formation. Although this formation contains abundant petrified wood, its floral composition has been virtually unknown. Three genera have been identified in this study: Protopiceoxylon Gothan, Mesembrioxylon Seward, and Taxaceoxylon (Unger) Krausel. Protopiceoxylon has only been reported once before from strata of the Jurassic age in North America (Knowlton, 1900). Mesembrioxylon and Taxaceoxylon have not been reported previously from the Jurassic of North America.

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