No description available.

Thesis--University of Wisconsin--Madison. / Typescript. Vita. Description based on print version record. Includes bibliographical references (leaves 158-165).

The hydrocarbon producing rocks of the Upper Jurassic in the northern Gulf of Mexico are known to contain lithium-rich brines. However, the genesis of the lithium-rich water is not very well understood. Analysis of hydrogeochemical data indicates that the brines are enriched in bromide, Calcium, Lithium, and sodium, and depleted in potassium, magnesium, and sulfate. Considering this, hydrogeochemical, petrographic, and X-ray Powder Diffraction (XRD) data shows that the brines have been significantly altered relative to the original composition of the water, by salt dissolution, freshwater mixing, and dolomitization. Based on the results of this study, the ore-grade lithium brine is being enhanced by the same stratigraphic and geochemical controls that is depositing dolomite in the Upper Jurassic reservoirs of the northern Gulf of Mexico.

The Upper Devonian Grosmont shelf complex is the worlds largest heavy oil deposit hosted in carbonates, with an estimated >50 billion cubic meters (318 to probably 406 bbls) of initial volume in place. At present the Grosmont is not yet under production. This study involves log interpretation, core examination; facies description; strontium, sulphur, carbon, and oxygen isotope analysis. The Grosmont is subdivided into four shallowing-upward cycles. Most Hondo evaporites are part of the Upper Grosmont 3 and Lower Grosmont and were deposited in a series of small, shallow subaqueous brine ponds or in an extensive lagoon. In the eastern part of the area, the Hondo appears to be dissolved resulting in solution-collapse breccias. Other diagenetic processes that were important in shaping the present reservoir characteristics were pervasive dolomitization and dolomite recrystallization, fracturing, and karstification.

No description available.

No / The Raman spectroscopic biosignatures of halotrophic cyanobacterial extremophiles from sabkha evaporitic saltpans are reported for the first time and ideas about the possible survival strategies in operation have been forthcoming. The biochemicals produced by the cyanobacteria which colonise the interfaces between large plates of clear selenitic gypsum, halite, and dolomitized calcium carbonates in the centre of the salt pans are identifiably different from those which are produced by benthic cyanobacterial mats colonising the surface of the salt pan edges in the intertidal zone. The prediction that similar geological formations would have been present on early Mars and which could now be underlying the highly peroxidised regolith on the surface of the planet has been confirmed by recent satellite observations from Mars orbit and by localised traverses by robotic surface rovers. The successful adoption of miniaturised Raman spectroscopic instrumentation as part of a scientific package for detection of extant life or biomolecular traces of extinct life on proposed future Mars missions will depend critically on interpretation of data from terrestrial Mars analogues such as sabkhas, of which the current study is an example.

Factors controlling cyclic sedimentation are discussed in a parallel study of two evaporite-bearing sequence, the Zechstein of Germany and the Silurian Salina Group of the Appalachian Basin. The Zechstein sequence was deposited in a basin that had received the debris swept in from the Variscan orogenic zone. The deposition of the evaporite-bearing sequence took place during a period of tectonic calm, preceded and succeeded by mild late Variscan movements. The sequence is divided into four major cycles by shale horizons accompanied and basinwards partially replaced by dolomites and anhydrites. Halite is the dominant sediment, it contains beds of anhydrite and potash salts, less commonly of shale, forming with the halite sedimentary cycles of diverse magnitudes. The Salina Group has been deposited in a basin that had previously received debris from the Taconic orogenic zone. The last orogenic movements had virtually ceased before the deposition of evaporites commenced. The evaporite-bearing sequence is divided into three major cycles by shale suites related to alluvial, fans of debris swept in from the previous orogenic zone. The shale beds are accompanied by dolomite beds containing stromatolitic horizons. The salt contains shale and dolomite beds of diverse thicknesses, giving rise to cycles of varied magnitudes. With increasing distance from the orogenic zone, the thinner shale interbeds in the salt grade into anhydrite. In contrast to the Zechstein sequence, in the Salina Group thicker anhydrite beds are rare and no potash zones have been found. The anhydrite deficiency is attributed by the author to bacterial reduction of the CaSO₄. The H₂S thus formed is in part retained in the sediments, in part it deposited FeS₂ or re-oxidized. The lack of potassium salts indicates a less inhibited communication with the open sea, as also witnessed by repeated incursions of marine fauna. In both sequences, most sedimentary cycles are controlled by the periodic entrance of diluted waters into the basin. Rain water enters directly as well as in the form of terrestrial run-off from the adjacent mountains, introducing mud and foreign ions, diluting and changing the ion ratios of the brines. Sea water enters the basin continuously or periodically, the concentration increases caused by the concomitant inflow of dissolved salts are mitigated by the reflux of more concentrated brines. Abrupt dilution of the brines by sea water followed by slow evaporation produces cycles of progressive solubility in the sediments resembling experimental successions. The periodic entrance of rain and sea water can be controlled by several factors. Increases in rainfall, particularly in the detritus source area, may reflect morphologically or astronomically induced climatic changes; the morphologic factors may in turn be controlled by tectonism, erosion and sediment accumulation. The ingress of sea water can be caused by intermittent subsidence in the bar area, or by a rise of sea level induced tectonically, glacio-eustatically, or simply by a change in wind direction. A few models involving parallel control of terrestrial and marine inflow are presented at the end.

Décollements are important tectonic elements in thin-skinned fold-thrust belts. However, few studies have addressed the internal structure of décollements because most are deeply buried and internal features typically cannot be resolved in seismic reflection images. Upper Jurassic evaporite exposures in the Potosí uplift of northeastern Mexico provide a unique tectonic window into the décollement of the Laramide-age Sierra Madre Oriental fold belt. In order to constrain the three-dimensional geometry of décollement structures, I mapped a ~20 km2 portion of the décollement at a scale of 1:10,000. I created a new stratigraphy for the décollement interval during mapping, and made detailed structural observations at targeted sites. The ~900 m thick décollement interval consists of gypsum with five carbonate members (up to 120 m thick) and numerous thin (<5 m) carbonate interbeds. These carbonate units delineate map-scale structural patterns and define two structural domains. The middle and upper parts of the décollement in the western domain contain map-scale folds with local map-scale boudinage and thrust faults. The eastern domain exposes the lower part of the décollement, and contains thrust repetitions of carbonate members and a regionally-persistent basal shear zone. These map relationships indicate a stratigraphic variation in structural style. Western domain folds and eastern domain thrust sheets both appear to be related kinematically to overburden folding. In contrast, the basal shear zone accommodated décollement-parallel shear strain in response to overburden translation. Folding and faulting of carbonate members and intervening gypsum units drove localization of simple shear into the basal shear zone, because only the lowermost gypsum interval maintained a favorable orientation sub-parallel to the regional transport direction throughout deformation. This investigation demonstrates that décollements have complex internal structural patterns that are below typical seismic resolution and lateral variations in structural style that cannot be reconstructed from single well cores or small outcrops. Décollement stratigraphy controls variations in strain magnitude within the décollement interval, so that previous models that invoke homogeneous strain within the décollement are incorrect. Complex, laterally-variable structural style and stratigraphic control of strain distribution could be general characteristics of décollements where the décollement interval contains significant contrasts in bed rheology. / text

Thesis (M.Sc.)--Memorial University of Newfoundland, 2004. / Bibliography: leaves 244-253. Also available online.

Au Nord-Est de l’Algérie, les sources thermales se situent dans une région de 53 500 km² de surface, qui s’étend sur une largeur de 473 km d’Ouest en Est, de Bejaia à El-Kala (frontière tunisienne), et sur une distance de 190 km du Nord au Sud. Elle comprend sept principales unités géologiques (nappes Telliennes, Chaine Calcaire, Néritiques, Sud Constantinois, Allochtone Sud-Sétifien, Parautochtone Autochtone, flysch). Cette thèse répond à un besoin de l’office national du tourisme Algérien qui souhaite en premier lieu la création de base de données regroupant plusieurs informations sur les sources, afin de faciliter le choix d’implantation d’infrastructures dédiées au tourisme thermal.Le contexte géologique est marqué par une structure géologique mise en place par des épisodes tectoniques (orogénèse Alpine) d’âge Priabonien à Turtonien. A ces événements, succèdent de grandes failles et des structures compressives. La méthodologie choisie pour déterminer l’origine de la minéralisation de ces eaux thermales s'appuie sur la synthèse des différentes études géophysiques et les recherches antérieures réalisées sur cette zone. Elles qui ont permis de préciser les structures et les caractéristiques géologiques générales des domaines du Nord Est Algérien dont la sismicité actuelle. L'analyse hydro-géo-chimique des eaux thermales constitue l'axe principal afin de déterminer les zones de recharge et les apports de mélange entre les différents types d’eaux chaudes et froides. Elle débouche sur l'utilisation des différents géothermomètres pour déterminer la température du réservoir profond.L’approche hydrochimique engagée repose sur deux campagnes de prélèvements qui ont été réalisées dans le cadre de ce travail ; la première a été effectuée dans la période des basses eaux au mois de septembre à octobre 2014, et l’autre a été réalisée dans la période des hautes eaux au mois de mai 2015. L'étude repose sur les mesures de terrain des paramètres chimiques et physiques non conservatifs (température, pH, conductivité électrique) et sur l'analyse des éléments majeurs, des traces, et de plusieurs isotopes (¹⁸O, ²H, ³H, ¹³C, ¹⁴C).Les diagrammes binaires et les traitements ACP menés sur les sources, dont un pourcentage élevé jalonne les grand accidents (failles), ont permis de distinguer 4 groupes d’eau géochimiquesUn groupe d’eaux (HCO₃⁻-Ca²⁺) très peu minéralisées se caractérise par des eaux ayant circulé dans des réservoirs carbonatés. Un second (HCO₃⁻-Na⁺) montre des phénomènes d’échange de base entre l’eau et les niveaux argileux. Un troisième (Cl⁻-Na⁺) ou (SO₄²⁻-Na⁺) montre un enrichissement en Na et Cl, qui traduit des circulations profondes avec échange chimique avec la matrice rocheuse sédimentaire évaporitique. Le dernier groupe (SO₄²⁻-Ca²⁺) ou (Cl⁻-Ca²⁺) a acquis sa minéralisation dans des formations Triasiques. / Pas de résumé