Publicação
Sedimentological signatures of extreme marine inundations
| Resumo: | This thesis aims to characterize (and distinguish) tsunami and storm deposits in the sedimentary record by focusing on the application of textural, morphoscopic, microtextural and compositional analysis, and establish their likely source materials. This work presents results from a variety of locations (Portugal, Indonesia and Scotland) and considers events of different chronologies and sources (AD 1755, 26 December 2004 and Storegga Slide tsunamis; Great Storm of 11 January 2005) that affected contrasting coastal settings with different regional oceanographic conditions. Typically these statigraphically peculiar (essentially sand-sized) deposits exhibited an abrupt basal contact, thinning and finning inland, massive structure and relevant lateral variation. Differentiation between tsunami and storm deposits was evidenced by the incorporation of rip-up clasts solely in the tsunamigenic deposits. Grain surface microtextural analysis proved to be a valuable complementary technique to be applied in the identification of extreme marine inundation deposits, especially when considered within a regional context. Tsunami and storm grains presented a more frequent presence of percussion marks and fresh surfaces when compared with potential source material. Generally the concentration of heavy minerals decreased up unit and in Salgados (Portugal) the assemblage presented similarities with dune samples. In Lhok Nga (Indonesia) and Boca do Rio (Portugal) it was possible to identify a mineralogical signature of the tsunami backwash. The assumption of a tsunami millennial return period for the Algarve (Portugal) coast was possible through the study of the lithostratigraphy of two locations affected by the AD1755. Overall results revealed that site-specific effects precluded clear-cut extrapolations on a storm vs tsunami emplacement mechanism of worldwide application although it demonstrated that the use of textural, morphoscopic, microtextural and heavy mineral data will enhance the criteria to recognize and differentiate these deposits if the regional context is sufficiently constrained. |
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| Autores principais: | Costa, Pedro José Miranda da, 1976- |
| Assunto: | Sedimentologia Tsunamis Tempestades Minerais pesados Teses de doutoramento - 2012 |
| Ano: | 2012 |
| País: | Portugal |
| Tipo de documento: | tese de doutoramento |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade de Lisboa |
| Idioma: | inglês |
| Origem: | Repositório da Universidade de Lisboa |
| Resumo: | This thesis aims to characterize (and distinguish) tsunami and storm deposits in the sedimentary record by focusing on the application of textural, morphoscopic, microtextural and compositional analysis, and establish their likely source materials. This work presents results from a variety of locations (Portugal, Indonesia and Scotland) and considers events of different chronologies and sources (AD 1755, 26 December 2004 and Storegga Slide tsunamis; Great Storm of 11 January 2005) that affected contrasting coastal settings with different regional oceanographic conditions. Typically these statigraphically peculiar (essentially sand-sized) deposits exhibited an abrupt basal contact, thinning and finning inland, massive structure and relevant lateral variation. Differentiation between tsunami and storm deposits was evidenced by the incorporation of rip-up clasts solely in the tsunamigenic deposits. Grain surface microtextural analysis proved to be a valuable complementary technique to be applied in the identification of extreme marine inundation deposits, especially when considered within a regional context. Tsunami and storm grains presented a more frequent presence of percussion marks and fresh surfaces when compared with potential source material. Generally the concentration of heavy minerals decreased up unit and in Salgados (Portugal) the assemblage presented similarities with dune samples. In Lhok Nga (Indonesia) and Boca do Rio (Portugal) it was possible to identify a mineralogical signature of the tsunami backwash. The assumption of a tsunami millennial return period for the Algarve (Portugal) coast was possible through the study of the lithostratigraphy of two locations affected by the AD1755. Overall results revealed that site-specific effects precluded clear-cut extrapolations on a storm vs tsunami emplacement mechanism of worldwide application although it demonstrated that the use of textural, morphoscopic, microtextural and heavy mineral data will enhance the criteria to recognize and differentiate these deposits if the regional context is sufficiently constrained. |
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