The relatively new method of using wavelets in well log analysis is a powerful tool for defining multiple superimposed scales of lithic trends and contacts. Interpreting depositional processes associated with different scales of vertical variation within well log responses allows prediction of the lateral extent of sands and the distribution of internal flow barriers important for development of oil field recovery strategies. Wavelet analysis of grain-size variations in a 2.1 km thick fluvial section including the fluvial Chinji and Nagri Formations, northern Pakistan, revealed three major wavelengths. Reliability of the wavelength values was tested and confirmed by multiple sectioning of the dataset. These dominant wavelengths are interpreted to reflect vertical variations within individual channels, the stacking of channel belts within overbank successions due to river avulsion, and larger-scale channel stacking patterns within this foreland basin that may reflect allocyclic influences. Wavelet analysis allows quantification of the scales of periodic vertical variations that may not be strictly cyclic in nature. Comparison of total wavelet energies over all scales for each depth to the grain size and sand percentages yielded good correlations with sand proportion curves. Although changes in the wavelet energy profile were much more distinct with respect to grain size, lithic boundaries' locations were not detected based solely on the total of the wavelet energies. The data were also analyzed using Fourier transforms. Although Fourier transforms of the data yielded the smallest scale cyclicities, the higher-order cyclicities were not defined. This comparison demonstrates the power of wavelet analysis in defining types of repetitive, but not strictly cyclic, variations that are commonly observed in the sedimentary record. Assessments of Milankovitch cyclicities were performed for the Chinji and the Nagri Formations using statistical and analytical analysis methods. A clear match between Milankovitch frequency ratios and vertical lithic variations was not observed, and thus distinct climatic control on cyclic lithological trends was not demonstrated. Analysis using wavelets to determine wavelet coefficients helps quantify characteristic scales of vertical variations, cyclicities, zone thicknesses, and locations of abrupt lithic boundaries. Wavelet analysis provides methods that could be used to help automate well log analysis.

The Middle and Upper Devonian (Givetian-Frasnian) shallow-water carbonate facies of western Europe were deposited as a large-scale transgressive succession over continental facies of the Old Red Continent. The transgression was in a northerly direction, reaching the southern Ardennes by the lower Eifelian and the Aachen area of Germany by the middle Givetian. Carbonate sedimentation continued through to the middle Frasnian, when a major pulse m relative sea-level rise drowned the platform. The carbonate platform had a complex internal structure, with three major palaeosettings. During the Eifelian, a storm-influenced homoclinal ramp existed over much of the Ardennes. Sedimentation was mostly open-marine in nature, with a protected back-ramp and tidal-Oats. The Givetian saw a transition from a ramp to shelf setting, with stromatoporoid reefs at the shelf edge providing protection for abroad shelf lagoon. The shelf had an ESE-WNW trend and extended from Boulogne (northern France) in the west to Aachen (western Germany) in the east. East of the river Rhine in the Rheinisches Schiefergebirge area of Germany, and in Southwest England, isolated carbonate complexes developed. These were positioned either on the shelf-edge, within the shelf or upon topographic highs within the basin. Synsedimentary tectonism and volcanism strongly influenced their development. As a result of their areal extent, lagoonal environments were studied extensively in shelf and isolated complexes. Palaeontology and sedimentology were used to identify 14 major microfacies within the lagoonal successions, which could be broadly categorised into four major groups. The semi-restricted subtidal microfacies group has a rich faunal assemblage which, although diverse, did not represent fully open-marine deposition. Sedimentation was entirely subtidal in nature. The restricted subtidal microfacies group is either characterised by monospecific fossil assemblages (chiefly molluscs or amphiporoids), or by macrofossil-poor facies. These facies represent poorly-circulated, subtidal environments which may have been subjected to flucmating salinities The intertidal microfacies group is characterised by fenestral limestones, which are commonly poorly-fossiliferous. Finally the supratidal microfacies group is typified by dolomudstones, microbial laminites and calcretes. A metre-scale cyclicity is prevelant in these lagoonal facies and two major types of cycle have been identified. Subtidal cycles show a decrease in circulation, decrease in diversity of organisms and increase in fluctuation of salinity upwards through the cycle. Peritidal cycles shallow upwards from a subtidal base through to an intertidal or supratidal cap. Subtidal cycles seem particularly common within the isolated carbonate complexes, yet both peritidal and subtidal cycles are identified in the shelf lagoon. The distribution of facies and cycles was controlled by a complex interaction of eustasy and differential subsidence. The setting (i.e., whether it was the shelf lagoon, or isolated carbonate complex) also influenced this distribution. Fischer plots were used successfully to correlate successions across the carbonate platform, and to identify areas of condensed or expanded sedimentation. Cycles were calculated to have a duration of approximately 42,000 years for the Upper Givetian. The magnitude of relative sea- level change was in the order of l-3m. The development of the metre-scale cyclicity is best explained by orbital forcing, yet this signature has been overprinted by autocyclic and tectonic noise. Third-order eustatic sea-level fluctuations were delineated by major marine transgressions, and a eustatic sea-level curve was established for the study area.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 83-87). Also available via the Internet.

Th. doct.--Terre, océan, espace--Lyon 1, 1994. / Bibliogr. p. 207-223.

No description available.

The Late Triassic platform carbonates of the Transdanubian Range, Hungary were part of a passive margin platform at the southwestern end of the Triassic Tethys now occurs in a single fault-bounded terrain. The Hungarian platform is made up of meter-scale, precessional (~20 k.y.) carbonate cycles. It contains a lower unit, the Main Dolomite Formation (600-1500m thick), which is totally dolomitized. It is overlain by the Transitional Unit (150-400m thick). The overlying Dachstein Limestone is up to 800m thick. The platform is a cyclic succession of subtidal carbonate, laminated tidal flat limestone or dolomitic caps, and reddish or greenish paleosols or reworked paleosols. The Triassic was a time of global greenhouse conditions and Milankovitch climate forcing has been well documented from lakes and off-shelf facies. The Triassic Hungarian carbonate platform records an imperfect Milankovitch eustatic signal. They lack the bundling of 5 precessional cycles into 100 k.y. eccentricity cycles or 20 cycles/400 k.y. bundle. This is interpreted to be due to many missed beats evidenced by caliches and paleosols, and thick amalgamated subtidal carbonates. These result from precessional sea-level fluctuations either not flooding the platform, or flooding it too deeply to allow shallowing up to sea-level in one precessional beat. Spectral analysis of the Hungarian carbonates was used to compare the amplitude spectra of different time series including lithology, gamma ray, self potential and neutron density. The spectra based on lithology were compared to synthetic spectra generated by computer from platforms subjected differing Milankovitch signals. Most dolomitization of the Hungarian carbonates occurred early in tidal flat settinfs during each high frequency cycle. Intertidal-supratidal dolomites are fine grained, Fe²⁺ and Mn²⁺ rich and slightly enriched in δ¹⁸O compared marine calcite cement, and formed from weakly to moderately reducing marine waters. Subtidal dolomites are slightly coarser grained, low in Fe²⁺ and Mn²⁺ and have heaviest d¹⁸O signatures, indicating more evaporative oxidizing brines beneath flats. Repeated emergence stabilized the dolomites to low Sr²⁺ and Na⁺ types similar to Cenozoic dolomites. Later, coarse-grained dolomites with very low Mn²⁺ Fe²⁺ and light δ¹⁸O signatures were formed along the platform margin by thermally driven, warm oxidizing marine water associated with Jurassic rifting of the Pennini Ocean (Neo-Tethys). The overall vertical distribution of early dolomite on the platform does not reflect long term ecstasy. Instead the regional stratigraphic trends in climatically sensitive sediments, as well as stable isotopes, suggest that intense dolomitization of the lower platform reflects a semi-arid, hot subtropical setting and megamonsoonal climate. Global cooling and increased humidity toward the latest Triassic and Early Jurassic, inhibited pervasive early dolomitization, leaving the upper platform little dolomitized. / Ph. D.

Statistical analyses of palynomorph assemblages from the Upper Cretaceous Bridge Creek Member (Greenhorn Formation) near Pueblo, Colorado suggest that the micritic limestone/organic rich-shale cycles of the Bridge Creek may have been caused by a combination of fluctuating primary productivity and humid/arid climate cycles. Species richness and evenness indices for palynomorph assemblages from 24 Bridge Creek beds were statistically analyzed using Analysis of Variance. The results indicate that assemblages for the limestone beds exhibit greater evenness and richness indices than do assemblage from the shale beds. Because phytoplankton communities typically exhibit lower evenness and richness values in eutrophic conditions, these results are consistent with possible surface water eutrophication during times of shale deposition. During times of high primary productivity, the aerobic oxidation of large amounts of organic matter settling to the sea floor may have consumed the oxygen available at depth creating an anaerobic environment and facilitating the preservation of organic carbon. Riverine input to the seaway also contributed to cycle production. It appears that shale was deposited during humid periods when riverine runoff provided terrigenous material necessary for shale deposition. The flow of isotopically-light fresh water to the seaway during times of shale deposition is supported by lighter 𝛿¹⁸O values in the shale beds. The fluctuating primary productivity and humid/arid cycles may have been caused by Milankovitch Cycle-driven climate change. Climate models indicate that insolation fluctuations driven by the precessional or obliquity cycle may have periodically increased upwelling along the eastern margin of the Cretaceous Interior Seaway and influenced rainfall patterns. At appears that organic rich shale was deposited when upwelling, nutrient-rich bottom water stimulated planktonic productivity and rainfall transported terrigenous material to the seaway. / Master of Science

The Azeri, Chirag, Gunashli (ACG) field is located offshore Azerbaijan. The reservoirs are multilayered sandstones forming traps within a major anticlinal structure. Proven crude oil reserves are estimated to contain 5.4 billion barrels of oil. In the past this area has been studied in regional detail but not at the reservoir scale with respect to the fluvio-deltaic sediments filling the northern shore of the ancient South Caspian Sea. The aim of this study is carried out the sedimentological, cyclostratigraphical analysis and reservoir characterization of Balakhany X Formation within the Productive Series which is considered to be one of the significant producing horizons. To be able to achieve this objective, a 30m thick section, which is mainly composed of siliciclastics, has been studied in detail on Balakhany X cores from C01 well Azeri field. In this study, detailed lithofacies analyses were performed and sandstone, mudstone, siltstone facies were recognized in the studied interval of the Balakhany X Formation. Litharenites and sublitharenites sandstones are the most abundant in the succession. Sedimentological analysis such as grain-size sphericity, provenance, XRD, SEM and grain surface texture were performed and their relationship with depositional environment were discussed. The grain size distribution of the samples along the succession shows distribution of fine to very fine sands. Sorting of sandstones ranges between moderately well to very well sorted. The provenance analysis of sandstones based on modal analysis of thin sections related to recycled orogen. According to interpretation of grain size parameters and grain surface textures analysis the main transporting agent of sands observed as wind, wave and river agents. High resolution cyclostratigraphy studies based on cm-m scaled cyclic occurrences of lithofacies along the measured section were performed. Milankovitch, sub-Milankovitch and millennial cycles were determined along the studied section. The petrophysical analysis revealed good to very good (18 to 24%) porosity and good permeability (10 to 538mD) in Balakhany X Formation. The porosity and permeability are affected by both textural and compositional controls. Grain size distribution along the reservoir section is fine to very fine sands. Influence of compaction was observed by the fractures and dissolutions on the sand grains. The calcite cement, grain-size variation, sorting and compaction are the main factors controlling porosity and permeability.

The Dolomite Alps of northern Italy are a classic field locality in the development carbonate stratigraphic theory. Included in the many discoveries rooted in the geology of the Dolomites is the concept of a hierarchy of stratigraphic forcing in the Alpine Triassic. The hierarchy states that carbonate sedimentation is dominantly a record of eustasy, resulting in organized stacking patterns, and that these stacking patterns reflect the interplay between low frequency (1-10 my) eustatic cycles and their component bundled high-frequency (100 & 20 kyr) eustatic cycles. The overall aim of this study is to further investigate the validity of the hierarchical model after recent dating of Anisian and Ladinian successions called the Milankovitchian periodicity and/or allocyclicity of the cyclic series into question. The study was completed using four sub-studies, 3 based on data collected in the field and a fourth based in cycle theory and computer modeling. First, it can be shown that allocyclic forcing exists in the Anisian/Ladinian platforms of the Dolomites by comparing the stratigraphic sections measured from 2 time-equivalent, independent carbonate platforms, the Latemar and Mendola Pass. Second, computer modeling of Anisian/Ladinian carbonate platform stratigraphy using Milankovitchain solar insolation as a proxy for high-frequency eustasy shows that both pure Milankovitch forcing and mixed Milankovitch/sub-Milankovitch forcing will produce synthetic carbonate platforms with stratigraphic successions comparable to those of the Anisian/Ladinian platforms of the Dolomites. Third, it can be shown that the while the Norian Dolomia Principale (a regional carbonate shelf) was affected by differential subsidence, megacycles systematically increase in their number of component cycles from 2-3:1 in the eastern Dolomites (updip) to 5-6:1 in the western Dolomites (seaward). In conclusion, the concept that carbonate platform stratigraphy is a record of an interplay between eustasy, subsidence, and sedimentation is upheld, while the validity of Milankovitchian forcing acting on all Alpine carbonate cycles is questioned. Instead, cyclic carbonates with sub-Milankovitch periodicities were common in the early and mid-Triassic, while cycles with Milankovitchian periodicities were common in the late Triassic. / text

Une calibration orbitale du Valanginien et d’une partie de l’Hauterivien (Crétacé inférieur) est présentée au cours de ce travail. Celles-ci sont basées sur l’identification des cycles de l’excentricité à partir d’analyses spectrales menées sur des proxies climatiques mesurés à haute résolution sur des alternances marne/calcaire hémipélagiques.Cinq coupes de référence sont analysées dans le Bassin Vocontien (Sud-Est de la France), couvrant l’ensemble de l’étage du Valanginien. Une durée de 5,08 Ma est proposée pour cet étage à partir de l’identification du cycle de l’excentricité de 405 ka. Le cadre temporel proposé, combiné aux âges radioisotopiques disponibles, montre que la perturbation en 13C du Valanginien moyen (événement Weissert) est antérieure à la mise en place des trapps du Paraná-Etendeka. La forte expression de l’obliquité dans la partie supérieure du Valanginien pourrait refléter la mise en place de calottes polaires de faible extension.La transition Hauterivien-Barrémien de Río Argos (Sud-Est de l’Espagne) est traitée par une analyse multi-proxies (cortèges argileux et susceptibilité magnétique ou SM). Par comparaison avec les bancs calcaires, les interbancs marneux sont enrichis en kaolinite et en illite, appauvries en smectite et possèdent de fortes valeurs de SM. Cela reflète des conditions tropicales humides lors du dépôt des marnes tandis que les calcaires se déposent en climat semi-aride. Les durées des zones d’ammonite à P. ohmi et à T. hugii sont respectivement estimées à 0,78 Ma et 0,54 Ma. L’événement anoxique Faraoni a une durée comprise entre 100 et 150 ka. Par corrélation avec d’autres coupes, Río Argos apparaît être le meilleur candidat GSSP / Orbital floating time scales are proposed for the Valanginian Stage and part of the Hauterivian Stage (Early Cretaceous). These are based on the identification of the eccentricity cycles from spectral analyses performed on high-resolution climatic proxies measured on hemipelagic marl-limestone alternations. Five reference sections were analysed in the Vocontian Basin (SE France), spanning the entire Valanginian. A duration of 5,08 myr is proposed for the Valanginian Stage from the identification of the 405-kyr eccentricity cycle. The time frame proposed, combined with available radiometric ages, shows that the mid-Valanginian 13C positive excursion (namely the Weissert Event) occurs prior to the onset of the Paraná-Etendeka traps. The stronger expression of the obliquity cycles in the upper part of the Valanginian Stage may be caused by the onset of low-extension polar ice. The Hauterivian-Barremian transition of the Río Argos section (SE Spain) was studied by a multi-proxies analysis (clay minerals, magnetic susceptibility or MS). Compared to limestone beds, marl interbeds are enriched in kaolinite and illite, impoverished in smectite and show stronger MS values. This reflect tropical humid conditions during marl deposits while limestone were deposited under semi arid conditions. The durations of the P. ohmi and T. hugii ammonite zones are assessed at 0.78 myr and 0.54 myr, respectively. The duration of the Faraoni anoxic event ranges from 100 to 150 kyr. By correlation with other sections, the Río Argos section appears to be the most valuable candidate for GSSP.