The sedimentological evolution of the Statfjord Formation of the Viking Graben at the Triassic - Jurassic transition is detailed by integration of studies of mineral assemblages, isotope age data, sedimentological core analysis, palaeosol / mineralogical wireline analysis and regional correlation of subsurface wireline information, combined with theories on basin evolution in continental settings. The aim of this study is to enhance the description of, and correlation within, hydrocarbon reservoirs developed within intra-continental alluvial sediments which have been deposited in areas above the knickpoints of coastline attached incised valleys, where there is a paucity of biostratigraphical information. Sedimentological analysis of core, wireline suites and production data, allow a stratigraphic framework to be erected which can delineate reservoir flow units. In the absence of palynological datums, chronostratigraphic correlation is done by heavy mineral and geochemical analysis, distinguishing between individual flow units allowing a more genetic correlation between related sands to be made. These analytical studies also point the stratigrapher to a more accurate regional geomorphic interpretation of the core by defining units which have the same provenance, thus allowing comparison of differing sedimentological criteria within single fluvial or floodplain units. At a smaller scale, a short outcrop study of the Castisent Formation of the Spanish Pyrenees was done to illustrate the intra-alluvial sheet sand complexity present in subsurface hydrocarbon reservoirs of alluvial origin. Using data mainly from the Brent Field, Statfjord Field and Snorre Field a model for the regional evolution of the Statfjord Formation is developed. Regional correlation of the reservoir units within the Statfjord Formation, using the methods discussed above, demonstrates basic geomorphic principles which are specifically concerned with the regional development of aggradational and erosive alluvial suites in settings inland from coastal areas.

Recent studies have demonstrated the potentially robust nature of U-Pb and Pb/Pb systematics within certain sedimentary and metamorphic carbonates (e.g. Moorbath et al., 1987; Jahn, 1988; Jahn et al., 1990; DeWolf and Halliday, 1991). During the course of this work, the Pb/Pb dating technique has been applied successfully to the direct dating of Proterozoic stromatolitic carbonates from Western Australia and India, Silurian stromatoporoidal carbonates from Sweden and Archaean marbles from India, permitting the direct age determination of depositional/early diagenetic, late diagenetic and metamorphic events. Results indicate that large variations in μ value (²³⁸U/²⁰⁴Pb) and virtually homogeneous initial Pb isotopic compositions are a recurrent feature of sedimentary and metamorphic carbonates. Authigenic marine carbonates may incorporate U and Pb through a variety of geochemical mechanisms; <ul> <li>organic complexing;</li> <li>crystal lattice substitution;</li> <li>adsorption onto particulate oxyhydroxides and</li> <li>early diagenetic reduction.</li> </ul> Since modern and ancient carbonates have U and Pb concentrations of the order of ppm, whereas dissolved U and Pb in the oceans occur at 3.2 ppb and 0.003 ppb, preconcentration within the water column must be an important factor in the establishment of appropriate geochemical conditions. The rapid scavenging of Pb, compared to rates of U fixation under suboxic conditions, means that depositional μ values seldom approach the sea water figure of c.80,000. Owing to the largely independent geochemical behaviour of U and Pb, early diagenetic, late diagenetic and metamorphic recrystallisation may either partially disturb Pb/Pb and U-Pb systematics or effect complete resetting of radiometric ages. Consequently, results from geochronological studies should be interpreted only after due consideration of all available geological information. The extensive distribution of metamorphic and sedimentary carbonates throughout the geological record, coupled with the apparent robustness of Pb/Pb systematics, means that this technique can offer an effective means of event dating, stratigraphic correlation and time scale calibration, particularly in the Precambrian where independent age constraints are limited. In addition, the identification of late diagenetic recrystallisation ages offers exciting potential for constraining the diagenetic histories of sedimentary basins.

No description available.

Extrusive carbonatites are rare igneous rocks with just 37 known localities. The majority are calciocarbonatites, the principal exception being those of the active volcano, Oldoinyo Lengai, which are strongly alkaline. Unresolved questions concerning extrusive carbonatites include: 1. Why are extrusive carbonatites at Lengai chemically different from all others? 2. Could the extrusive calciocarbonatites originally have had alkaline compositions? In order to address these questions extrusive carbonatites from both Lengai and the adjacent volcano, Kerimasi, were collected and compared. A compilation of all the available data on known extrusive carbonatites is also presented. The major results documented in this thesis are: 1. Alkali carbonatites from Oldoinyo Lengai erupted in 1993 contain petrographic evidence for an origin by liquid immiscibility from a highly fractionated peralkaline silicate melt (wollastonite nephelinite). 2. The suite of silicate rocks at Kerimasi are derived from a primary olivine nephelinite by fractional crystallisation and cumulus processes. 3. Extrusive carbonatites at Kerimasi are not genetically related to the silicate suite. By contrast intrusive sovites also present, originated by liquid immiscibility from a primitive silicate magma, equivalent to a melilite, nephelinite, at low pressure. 4. Extrusive calciocarbonatites from Kerimasi were erupted directly from the mantle. They contain phenocrysts (previously interpreted as pseudomorphs after alkali carbonate) which are now thought to have been dolomite containing calcite exsolution lamellae. 5. Of the 35 other extrusive carbonatite occurrences, none show any petrographic or geochemical evidence of having originally being alkaline. Therefore extrusive carbonatites from Oldoinyo Lengai are thought to be unique. 6. Of the 37 extrusive carbonatites, 50% are associated with melilitites or melilitebearing rocks, 27% are associated with nephelinites and the remaining 23% were erupted with no associated silicate magmas.

No description available.

No description available.

Typescript. / Thesis (M. S.)--University of Hawaii, 1969. / Bibliography: leaves 103-107. / vii, 107 l illus

The structure and petrology of Upper Precambrian and Cambrian rocks have been studied in detail, in an area 38 miles north - east of Adelaide, South Australia. The rocks occur within a broad zone of high grade metamorphism on the eastern side of the Mt. Lofty Ranges. The Upper Precambrian succession consists predominantly of pelitic and semi - pelitic schists, quartzites, calc - silicate rocks and calc - schists, and the Cambrian sequence of quartzo - feldspathic schists, migmatites, granite gneiss, calc - silicate rocks and minor pelitic schists and quartzites. The rocks have reached the sillimanite grade of metamorphism and the metamorphism is of the low pressure - intermediate type. Dolerites, pegmatites, minor granodiorites and granites intrude the meta - sediments. Mineralogical and structural relationships of the granite gneiss, indicate that it has been formed by recrystalliaation of the quartzo - feldspathic schists. Small scale metamorphic differentiation, appears to have accompanied the recrystallization. The migmatites are believed to have been formed by metamorphic differentiation rather than by anatexis. Three phases of deformation are recognised in the Upper Precambrian rocks and two in the Cambrian. The second deformation recorded in the Upper Precambrian rocks does not appear in the Cambrian rocks. Each deformation has been accompanied by the formation of foliation. In the Proterozoic rocks deformed by the second and third phases of folding, the foliation is a crenulation cleavage. The deformations in both the Upper Proterozoic and Cambrian sequences are considered to be related. Petrofabric studies of quartz, scapolite and biotite are related to the respective macroscopic structures. An analysis of the chronology of crystallisation and deformation of these rocks indicates that crystallisation continued during and after each phase of deformation. Faulting commenced either prior to or during meta - morphism. Intense metasomatic activity followed a later phase of faulting resulting in the widespread development of albitites and in some cases talc ore bodies. The albitites formed in the fault zone were subsequently brecciated by further movement and later healed by the introduction of more metasoinatic fluid. / Thesis (Ph.D.) -- University of Adelaide, Department of Geology, 1966.

Thesis (M.S. - Hydrology and Water Resources)--University of Arizona, 1984. / Includes bibliographical references (leaves 154-156).

Thesis (M.S. - Hydrology and Water Resources)--University of Arizona, 1984. / Includes bibliographical references (leaves 139-141).