CEU Electronic Theses and Dissertations, 2022
| Author | Portányi, Elsa Marie |
|---|---|
| Title | Geochemistry of Insular Shelves: Santa Maria Island, Azores, Portugal |
| Summary | The insular shelf of an island is the portion of submerged land that gradually extends into the open ocean with the edge of the shelf marking the point of erosion from a previous, lower, sea-level (Quartau et al., 2014). The morphology of these features provides themselves as records for wave erosion and volcanic progradation. On a microscopic level, the distribution of shelf materials is reliant on ominous systems such as ocean currents, climate, and chemical reactions which determine their movement, form, and abundance in a given area. Ocean currents provide an energy source for the weathering of materials in its path as well as a vessel for their distribution. The climate surrounding the island also provide conditions that weather, either by precipitation or through desiccation. The outcome of these interactions depends on the chemical composition of the force as well as that of the material receiving its impact. It is by systems (climate, currents, geology) and their products (volcanic and carbonate minerals) that researchers can recreate the history of a landmass, understand its present mixing, and predict its future. The shortage of hybrid land and off-shore studies has been a topic of researchers (i.e. Amorim et al., 2017 & Quartau et al. 2015). One theory is the lack of multidisciplinary models which bridge the gap between volcanology and oceanography (Amorim et al., 2017). Alternatively, attention has been brought to the preference of offshore studies that focus on slopes and deep ocean rather than the insular shelf (Quartau et al., 2015). In the pursuit to address this deficit the Portuguese Science Foundation (FCT) put into effect the PLATMAR (Platform Santa Maria) project. The objective of PLATMAR is to collect a globally competitive dataset of the geological and geophysical systems of Santa Maria Island of the Azores archipelago. In pursuit of these aims, PLATMAR offers opportunities for academic research projects which will contribute to their overarching goal- understanding the development of the island’s slope and shelf. In order to contribute to the overarching goal of PLATMAR, this work studied the distribution, form, and origin of volcanic and carbonate materials on the insular shelf of Santa Maria Island. Twelve sites were selected with varying depths and distances from shore and grouped based on their geographical position- Southwest (SW), Southcentral (SC), Southeast (SE) and North (N). Methods of X-ray fluorescence, X-ray diffraction, Loss on ignition, total organic carbon solid sample module and gas chromatography-mass spectrometry were used to identify elements, minerals and forms as sites transition along shelf transects. Mineral analysis identified augite and anorthite as the volcanic materials contributing to the shelf. Concentrations of these minerals were highest in the SW and absent in the N. Carbonate minerals (calcite and aragonite) were found to be the largest contributors to the total shelf composition, nearing almost pure values in the N and SC transects. The differences in climate and maritime conditions around the island have been identified as Portanyi, MESPOM ii determining factors of the distribution and extent of the constituent’s presence. The west, facing windward, experiences more frequent precipitation which is linked with higher tidal zones, and potential energy for weathering. The east, leeward, is drier using desiccation as a mode of weathering. The northern sites, the furthest sites from the shore, were almost entirely void of terrestrial materials and largely rely on carbonates for its current composition. The southcentral transect also exhibited higher values of carbonate to volcanic ratios, however, it is suspected that this may be the result of the limitations which come from the sample size. The niche of these studies can provide essential information needed for the understanding in the geological history island volcanoes, their present state, and their future trends. |
| Supervisor | Mitchell, Neil; Van Dongen, Bart |
| Department | Environment Sciences and Policy MSc |
| Full text | https://www.etd.ceu.edu/2022/portanyi_elsamarie.pdf |
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