HR: 18:05h
AN: T24A-08    [Abstracts]
TI: Geological recognition of tsunami and storm deposits in two coastal areas of Portugal
AU: * Costa, P J
EM: pedrojmcosta@ist.utl.pt
AF: Earthquake Engineering and Seismology Division, ICIST, Instituto Superior Técnico, Technical University of Lisbon, Avenida Rovisco Pais, Lisbon, 1049-001, Portugal
AU: * Costa, P J
EM: pedrojmcosta@ist.utl.pt
AF: Department of Geography and Earth Sciences, Brunel University, Kingston Lane, Uxbridge, UB8 3PH, United Kingdom
AU: Leroy, S A
EM: suzanne.leroy@brunel.ac.uk
AF: Department of Geography and Earth Sciences, Brunel University, Kingston Lane, Uxbridge, UB8 3PH, United Kingdom
AU: Fonseca, J F
EM: jfonseca@ist.utl.pt
AF: Earthquake Engineering and Seismology Division, ICIST, Instituto Superior Técnico, Technical University of Lisbon, Avenida Rovisco Pais, Lisbon, 1049-001, Portugal
AU: Fonseca, J F
EM: jfonseca@ist.utl.pt
AF: Physics Department, Instituto Superior Técnico, Technical University of Lisbon, Avenida Rovisco Pais, Lisbon, 1049-001, Portugal
AB: Abrupt marine invasions such as tsunamis and storms are particularly devastating for coastal areas. They may also leave a permanent record in sedimentary deposits. In historical times the most destructive tsunami that affected Europe was the Lisbon AD 1755. This presentation aims to contribute to a better understanding of the signature left by abrupt marine invasions in coastal stratigraphy by investigating the nature of the sedimentary record associated with tsunamis in a region of their known impact. The techniques used include stratigraphic description, grain size analysis, digital and x-ray photography, magnetic susceptibility, macrofossils analysis, geochemical analysis and 210Pb and Optically Stimulated Luminescence dating. The investigated areas (e.g. Lagoa de Óbidos (Central Portugal) and Martinhal (South Portugal)) were affected by the AD 1755 tsunami. The locations have similar geomorphological features and are both susceptible to major abrupt marine invasions. Results show that an abrupt event deposited unique sedimentary units in both locations. A similar age for the event was established. A considerable number of tsunami sedimentary characteristics, (stratigraphical, granulometric, palaeontological and geochemical) were detected in both sites. Moreover, other abrupt marine invasions were detected in the lithostratigraphy of the two areas. However, a key outcome of this research is the demonstration of the difficulty of distinguishing between sedimentary deposits laid down by tsunamis, and those deposits resulting from storm action.
DE: 0545 Modeling (4255)
DE: 3020 Littoral processes
DE: 4558 Sediment transport (1862)
DE: 4564 Tsunamis and storm surges
DE: 7221 Paleoseismology (8036)
SC: Tectonophysics [T]
MN: 2007 Joint Assembly