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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

An early Permian subtropical carbonate system : sedimentology and diagenesis of the Raanes and Great Bear Cape formations, Sverdrup Basin, Arctic Canada

Bensing, Joel P. 29 August 2007 (has links)
The Early Permian (Sakmarian to Kungarian) Raanes and Great Bear Cape formations of the Sverdrup Basin were deposited at a time of ocean cooling, and are interpreted to reflect a subtropical setting. Pelmatozoans, bryozoans, and brachiopods are the predominant fossils throughout the extent of these two units, with local occurrences of large fusulinids and colonial corals. This mixed photozoan-heterozoan assemblage is similar to the sediments of modern-day subtropical settings. Although the Raanes and Great Bear Cape have warm-water rocks below, and cool-water rocks above, the fossil assemblages in these formations were dependent upon changes in oceanography and sea-level. Three distinct phases, as determined by water depth and temperature, occur. First, the rocks of the Raanes and lower Great Bear Cape are deep water and heterozoan in nature. Second, the middle Great Bear Cape limestones record a time of shallow, subtropical waters. Finally, the upper Great Bear Cape is shallow-water, but cooling had progressed to a point that precluded the occurrence of any photozoan components, regardless of depth. Due to evolutionary changes in other subtropical biota, the most reliable fossil indicator of subtropical deposition in the rock record is large benthic foraminifera (including fusulinids) in an otherwise heterozoan assemblage. The identification of limestones representative of these conditions should, therefore, be identifiable at times in the Earth’s history when large benthic foraminifera lived in shallow marine environments. The Great Bear Cape Formation subtropical facies underwent post-depositional changes that are manifest as calcite cements, iron-oxides, glauconite, and silica. Isopachous calcite cements precipitated in intraskeletal pore spaces as well as around the outside of grains. Glauconite, which is an authigenic marine mineral, has been oxidized to iron oxide, and both minerals post-date, or are included within, the isopachous cements. The isopachous cements must, therefore, have also formed in the marine environment. Where they are precipitated around pelmatozoan fragments, these originally high magnesium calcite cements have been neomorphosed to single-crystal epitaxial cements at the same time as mineral stabilization of the biofragments. These cements then seeded the growth of further epitaxial cement in the meteoric environment. / Thesis (Master, Geological Sciences & Geological Engineering) -- Queen's University, 2007-08-21 10:58:18.958
2

Using Detrital-Zircon Geochronology and (U-Th)/He Thermochronology to Re-evaluate the Triassic-Jurassic Tectonic Setting of Northern Laurentia, Canadian Arctic

Midwinter, Derrick January 2016 (has links)
New geochronological and field data were examined from Triassic-Jurassic strata in the Sverdrup Basin, Arctic Canada. Detailed analysis of detrital-zircon data identified a pronounced near-syndepositional age-fraction in Triassic strata, which significantly is absent in Jurassic strata of the Sverdrup Basin suggesting a protracted history of magmatism and sediment dispersal from areas north of the basin during the Triassic. However, as a result of rifting, during the Early Jurassic, the northern source region became disconnected from the Sverdrup Basin, and opened the precursor basin (Amerasia Basin) to the Arctic Ocean. Jurassic rifting of the Amerasia Basin would have had associated rift-flank uplift. Time-temperature models produced from zircon (U-Th)/He thermochronological data elucidate the unknown thermal history between the regional Devonian-Cretaceous unconformity in the southwestern Canadian Arctic suggesting ~4 km of addition deposition on Banks Island and ≤1 km of deposition towards the craton interior.

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