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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

Relating Karst Development to Island Dolomite Formation using Petrography, Geochemistry, and Geomorphology

Sumrall, Jonathan 11 May 2013 (has links)
Three islands of study with differing types of dolomite were examined for karst features. Barbados showed that island dolomite could contain dissolutional karst features that form either during or after dolomitization. On Curacao, two types of dolomite were identified. The first documented occurrence of direct dolomite precipitation in situ was found using electron microscopy. Remnant voids from Curacao were classified and used to determine uplift and cliff retreat rates. On Isla de Mona, the influence of microbes in the mixing zone was added to the Dorag model of dolomite replacement. In addition, accounting for glacioeustasy, tectonic, and diagenetic fluctuations hypothesized large volume of dolomite. This study significantly contributes to the understanding of young dolomite formation and diagenesis as well as documenting dissolutional voids within island dolomite.
2

Analyses of Common Elements and Oxides in the Paleosols of the Bahamas and of the Northern Mariana Islands

Ersek, Vasile 07 August 2004 (has links)
Paleosols from the Bahamas and the Northern Mariana Islands (CNMI) are closely related to past atmospheric circulation and dust load. In the Bahamas the sources of insoluble residue (IR) must be allogenic because the islands consist of almost pure carbonates. The Al2O3:TiO2 ratio was used to establish the provenance of the IR of the paleosols. Comparisons of this ratio from Bahamian paleosols, North African dust, Lesser Antilles ash and North American loess reveal that the African dust is the major contributor to the IR, with a potential minor volcanic input from the Lesser Antilles. The contribution of the North American loess to the IR was not determined because of geochemical similarities with the North African dust. The study of two outcrops in Eleuthera indicate that paleosols can act as aquicludes. The Bahamian samples were collected on a roughly north-south transect in order to establish the climatic influence on paleosol properties. Even though there is a marked climatic gradient in the Bahamas, the paleosol geochemistry shows no trend that could be related to paleoclimate. While previous studies indicated that the source of insoluble residues in the soils of CNMI is carbonate dissolution, the present study shows that atmospheric deposition of ash from the Mariana arc and dust from the Asian continent may play a significant role in paleosol formation.

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