Thesis (M.S.)--University of Wisconsin--Madison, 1981. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 137-146).

Thèse--Sc. nat.--Bordeaux I, 1983. / Bibliogr. p. I-XXV.

No description available.

No description available.

Th.--Sci.--Bordeaux I, 1988. / 1988 d'après la déclaration de dépôt légal. Bibliogr. p. 203-223.

Thesis (M. Sc.)--University of Wisconsin, 1973. / "AD 770 825." Sponsored by the Office of Naval Research under Contract no. N00014-67-A-0123-0002, Nr 307-311/2-19-70, Code 415. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 93-97).

Turbidite-hosted gold deposits contribute a significant proportion to world lode gold production and have also provided substantial gold to alluvial resources. Turbidity current deposits occur throughout geological time within Archaean greenstone belts, Proterozoic orogenic belts and rifted passive continental margins, and Palaeozoic geosynclines. Representing the end member of the sedimentary cycle, turbidites have the attribute of preservation not only on an individual bed basis but also due to below wave base accumulation in submarine deeps. Cyclic deposition according to the Bouma sequence punctuates turbidite deposition by a series of diastems. Accumulation of organic, pelagic and chemical sediments may concentrate gold to protore enrichment levels i n a primary sedimentary environment. Dewatering during diagenesis and low-grade metamorphism under reducing conditions may redistribute gold with transport as low energy organo- and thio-complexes. Gold may precipitate with diagenetic pyrite and silica near black shale and/or partially replace fine carbonate detritus. Gold solubility increases with high grade amphibolite facies metamorphism (T 400ºC) when efficient leaching of gold and transport by simple chloro- and hydroxychloro - complexes to lower greenschist regions takes place. Reduced permeability of turbidite strata induces hydrofracturing which focuses dewatering solutions. Gold is deposited due to pressure and temperature decrease or local changes in physico - chemico conditions caused by the reaction of fluids with wall rocks (reactive beds in turbidites are predominantly carbonaceous strata). The largest of turbidite - hosted goldfields are confined to back -arc or marginal sea basins with restricted oceanic circulation. The richest concentrations of gold occur proximal to the original source within the greenschist facies formations lowermost in a thick turbidite sequence and exhibit strong combined structural and lithological association. Turbidites represent important strata for the concentration and preservation of gold not only during sedimentation and diagenesis but also during later deformation and metamorphism.

No description available.

No description available.

Research carried out in the Ediacaran of eastern Newfoundland focused on two projects: sedimentology of the Conception and St. John’s groups exposed on the Bonavista Peninsula; and taxonomic descriptions of the small, stemmed frondose fossils at Mistaken Point on the Avalon Peninsula. Sedimentological study of the upper Conception and lower St. John's groups at Catalina Dome on Bonavista Peninsula extends our understanding of the Conception Basin, in which the oldest known complex, deep marine organisms lived, by a factor of two. Mudstone-rich turbidites dominate the succession, and a lack of wave-generated structures or other shallow-water indicators support the interpretation that the depositional environment was deep-marine. The basal part of the succession contains seismoturbidites that show no evidence of horizontal translation, implying that deposition occurred on a flat basin plain. Strata higher in the succession exhibit horizontally slumped beds, implying a transition into slope deposition. Turbidite ripple marks show a change in paleocurrent direction from eastward to southward in the Trepassey Formation, consistent with a change from convergent to strike-slip tectonics that occurred diachronously across the basin. Volcanic ash beds are more common in the Catalina Dome succession than on the Avalon Peninsula, reflecting deposition closer to the volcanic source. These volcanic beds are associated with diverse fossil assemblages rich in rangeomorphs that locally persist into the Fermeuse Formation, in contrast with the Avalon Peninsula where the Fermeuse Formation contains only simple discoid fossils. This taphonomic window lends support to the hypothesis that the form genus Aspidella represents the holdfasts of Ediacaran fronds. Stemmed small frond fossils from Mistaken Point, Avalon Peninsula, have often been informally referred to as “featherdusters”, but due to their small size and consequent poor preservation, they have not until now been formally described. The small, stemmed fronds are more diverse than previously realized, and include representatives of taxa described from elsewhere in Newfoundland, juveniles of other Mistaken Point fronds, and two new monospecific genera. This biodiversity suggests that the basal elevated tier that the small fronds occupied was competitive, with convergent evolution of frondose taxa showing distinct architecture and constructions, but broadly similar size and shape. / Thesis (Master, Geological Sciences & Geological Engineering) -- Queen's University, 2013-10-30 12:12:23.297