Dearin, Angela (2007) Provenance of the Ben Nevis Formation sandstones, White Rose Field, Jeanne d' Arc Basin, Newfoundland, Canada. Masters thesis, Memorial University of Newfoundland.
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This study focuses on the changes of sediment provenance with time, within and adjacent to selected reservoir intervals of the Aptian Ben Nevis Formation in the White Rose Field, Jeanne d'Arc basin. The field contains both oil and gas, and the reservoir rock is a very-fine- to fine-grained, generally well-sorted sandstone with variable thicknesses of up to 300 m. Average QFL ratios for Ben Nevis sandstones are Q₈₉F₃L₈, with the major lithic components being detrital carbonate grains and chert. Based on subcrop patterns and relative grain sizes, the Tithonian-Berriasian Hibernia Formation sandstones and the Barremian-Aptian Avalon Formation sandstones are thought to be possible sediment sources. -- Tectonic discriminative diagrams as well as petrographic descriptions give evidence of a very small amount of feldspar and indicate that the Ben Nevis Formation is not a first cycle sediment; rather, abraded quartz overgrowths indicate that Ben Nevis Formation sandstones are polycyclic and were sourced from recycled sediments. In addition, the Chemical Index of alteration (CIA) diagram can be used to show that the original basement of igneous and/or metamorphic rocks that acted as sediment source for the Ben Nevis Formation must have been of granodiorite composition. -- The Avalon Formation is petrographically and geochemically similar to the Ben Nevis Formation. Cuttings samples show a similar grain size and chemical composition to the Ben Nevis Formation, indicating that the Avalon Formation is a plausible source for the Ben Nevis Formation without requiring significant reworking or alteration. -- Possible sources with a higher lithic component, such as the Hibernia Formation, imply geochemical alteration with only limited physical reworking of the rock, which removed a large portion of unstable lithic grains and increased the quartz content relative to feldspars and lithic grains, leading to the quartz-rich composition of the Ben Nevis Formation. This process is supported by trace element data and plots of SiO₂ against immobile elements, together with common exposures of Hibernia Formation below the Aptian unconformity. Together with erosion of the Upper Hibernia Formation, detrital carbonate grains may have been added from underlying A-marker and/or B-marker units. Based on weathering relationships inferred from CIA diagrams, the remaining (presently preserved) sections of Lower Hibernia Formation were ultimately sourced from a more mafic basement, which is not reflected in the composition of upper Hibernia, Avalon, and Ben Nevis Formation sandstones. -- The Ben Nevis Formation is a relatively homogeneous sandstone with very subtle changes both petrographically and geochemically. Grouping of similar Zr concentrations within the Ben Nevis Formation has shown three correlatable units throughout the White Rose Field. Trends on CIA diagrams indicate an increasing amount of weathering moving from the south to north, perhaps due to lower topographic gradients in the north, causing longer residence times and hence increases in chemical weathering. P/K ratios are also lower in the north area, indicating a mature sediment source during early transgression in the north which became progressively less mature as transgression moved southward.
|Item Type:||Thesis (Masters)|
|Additional Information:||Bibliography: leaves 160-168|
|Department(s):||Science, Faculty of > Earth Sciences|
|Geographic Location:||Canada--Newfoundland and Labrador--Jeanne d'Arc Basin; Grand Banks of Newfoundland; White Rose Oil Field|
|Library of Congress Subject Heading:||Sandstone--Newfoundland and Labrador--Jeanne d'Arc Basin; Sedimentation and deposition--Newfoundland and Labrador--Jeanne d'Arc Basin; Grand Banks of Newfoundland|
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