Frankfurt (Main), Universiẗat, Diss., 2003.

Two Paleoproterozoic basins, the western Thelon Basin, and the Otish Basin, Canada, were investigated using basin analysis to evaluate critical factors for the formation of unconformity-related uranium deposits. The results serve to guide ongoing exploration at two under-studied uranium prospects in each basin, and help predict whether or not these basins have the potential to host high-grade uranium deposits in other locations. Sequence stratigraphy, in combination with mineral paragenesis indicates that unmetamorphosed basinal sandstones overlying the Boomerang Lake prospect, western Thelon Basin, were compacted and occluded by kaolinite and muscovite during diagenesis, and became diagenetic aquicludes that were unable to effectively conduct uranium-bearing basinal brines. Based on the high δ18O values of basinal and basement-influenced fluids, and the preservation of pre-Thelon-Basin 40Ar/39Ar dates of poorly-crystalline phyllosilicates in the basement rocks, hydrothermal alteration and uranium mineralization must have occurred at low water/rock ratios. This produced uneconomic amounts of U-bearing phosphate that was misidentified as uraninite in a previous report. A significant uranium deposit is unprobable based on the lack of unsupported radiogenic Pb near the prospect. However, intersections of thick, stratigraphically-higher diagenetic aquifers, which are marked by abundant dickite, and structurally-reactivated basement rocks on a different exploration trend remain the most prospective locations for a uranium deposit in the area. At the Camie River prospect, Otish Basin, diagenesis of basinal sediments in thick diagenetic aquifers was associated with fluids that were isotopically similar to seawater-derived basinal brines. The 1721 ±20 Ma Pb/Pb date obtained for Camie River uraninite coincides with intrusions of the Otish Gabbro, which triggered basinal fluid flow in diagenetic aquifers and uranium mineralization throughout the basin. The effects of late hydrothermal, metamorphic, and meteoric fluid events are restricted to fractures and faults. These zones also preferentially host radiogenic Pb and pathfinder elements that dispersed from the prospect, which can be utilized to vector towards additional deposits. The unconformity-type deposit model can be extended to basins as old as 2.0 Ga, as the Otish Basin demonstrates that atmospheric oxygen contents were high enough at this time to allow the evolution of U-leaching oxidizing basinal brines. / Thesis (Ph.D, Geological Sciences & Geological Engineering) -- Queen's University, 2011-01-29 15:45:53.651

Seventy-eight low-altitude passes of MErcury Surface, Space ENvironment, GEochemistry, and Ranging magnetometer data from August to September of 2014 have been applied to produce an approximate map of the crustal magnetic field at a constant altitude of 80 km covering latitudes of 50°–80°N and longitudes of 160°–330°E. The strongest anomalies are located in the westernmost part of the mapped region just north and northeast of the Caloris impact basin. The strongest single anomaly group lies over a smooth plains unit that extends northward from Caloris. A second anomaly lies on the Odin Formation, interpreted as primary Caloris ejecta. A third broad anomaly also lies over a smooth plains unit, Suisei Planitia. Although many smooth plains on Mercury may have a volcanic origin, a subset of these plains is concentrated around Caloris and could have a dominantly impact origin. It is therefore proposed that many of the Mercurian anomaly sources consist of impact basin ejecta materials.

High-resolution (20-250 Hz) multichannel seismic (MCS) reflection data with record lengths of 4-8 s TWT, totaling approximately 4620 line km on the shelf and slope of the Sandino forearc basin of offshore western Nicaragua, were acquired in November-December 2004 (cruise EW04-12) and subsequently processed at the University of Texas Institute for Geophysics. Seismic sequence interpretation was conducted using these MCS data in conjunction with deeper penetration (16-20. s TWT) MCS profiles from a previous survey (cruise EW00-05). Age estimates were based on cuttings from intersecting industry wells. Structure and isochron maps were created for 16 sequences and used to identify structural and depositional trends within the Sandino basin. The Tectonostratigraphic evolution of the basin varies considerably along-strike and is divided into five general stages from Late Cretaceous to recent. Evidence for multiple episodes of terrane accretion is observed from Late Eocene to Late Oligocene and potentially during Mid- to Late Miocene as well. Stratal stacking patterns suggest the Nicaraguan margin has not been dominated by subduction erosion during its history and extensional features beneath the slope are interpreted to have originated as a result of processes related to collision of allochthonous terrane of the downgoing plate, sediment underplating, and slab roll-back. With more precise age control, the stable northwestern region of the Sandino basin, where sediment is relatively undeformed since Late Oligocene and measures ≥ 16 km thick, offers a unique convergent margin setting for investigations of forcings on sequence development. / text

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An integrated, multidisciplinary basin analysis has been carried out for an approximately isochronous stratal interval of the Silurian fill of the Welsh Basin. The selected interval is the Upper Llandovery <i>griestoniensis</i> Chronozone which represents a time interval of probably less than one million years. Two mapped areas with contrasting structural styles illustrate the heterogeneous response of the basin-fill to basin inversion and shortening. One major Welsh structure, the Central Wales Synclinorium, is shown to be related to a long-lived structural discontinuity which significantly influenced early Silurian sedimentation patterns. During extension/transtension in the basin this structure, as the edge of a tilted fault block, formed a palaeohigh. Turbidite systems were confined to either side and were ponded in relatively small-scale sub-basins defined by the tilted fault block geometry. In basinal facies of <i>griestoniensis</i> Zone age four major lithofacies associations are recognized: the channel-lobe transition, sandstone lobe, lobe fringe, and lateral basin-slope facies associations. They represent deposits of the outer area of a moderately large (minimum length of 100 km), elongate turbidite system and its bounding slope. Large scale erosional structures, filled with conglomerates and pebbly sandstones, occur in the more proximal areas of exposure. They are either channels or huge scours excavated by large volume turbidity currents undergoing hydraulic jumps. Lateral facies variations in sandstone lobes reflect down-system and cross-system variations in competence and capacity of flows. Palaeocurrent patterns and inferred onlap relationships reflect confinement by structurally-controlled slopes. Since the system developed during a time of widespread transgression sandstone lobes probably record pulses of rapid tectonic uplift at source. Unconformities, corresponding to times of active growth of depositional sandstone lobes in the basin, were generated on the southern basin margin. Lateral gradients in palaeo-oxygenation of bottom waters and fluctuations in oxicity through time are reconstructed using trace fossil evidence and diagenetic mineral assemblages. Relic downward-migrating oxidation fronts are recorded for the first time from ancient turbidites. A diverse trace fossil assemblage associated with the turbidite system is described and interpreted. Detailed logging through the basinal sequence reveals that times of dysaerobic bottom water conditions, during which turbidites and hemipelagites were reworked by soft-bodied infauna, alternated with periods of bottom water anoxia, during which laminated hemipelagites containing a pelagic fauna of graptolites were preserved. Such alternations may be very rapid, suggesting close proximity of the anoxic-oxic interface to the sediment surface, or may have far longer periodicities, reflecting periods of stable pycnocline development above anoxic bottom waters. Phosphate cements are shown to have initiated very close to the sediment surface beneath oxygen-deficient bottom waters in the basin.

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