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| Titel |
Recent high-energy marine events in the sediments of Lagoa de Óbidos and Martinhal (Portugal): recognition, age and likely causes |
| VerfasserIn |
P. J. M. Costa, S. A. G. Leroy, J. L. Dinis, A. G. Dawson, S. Kortekaas |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1561-8633
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| Digitales Dokument |
URL |
| Erschienen |
In: Natural Hazards and Earth System Science ; 12, no. 5 ; Nr. 12, no. 5 (2012-05-09), S.1367-1380 |
| Datensatznummer |
250010805
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| Publikation (Nr.) |
 copernicus.org/nhess-12-1367-2012.pdf |
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| Zusammenfassung |
| A key issue in coastal hazards research is the need to distinguish sediments
deposited by past extreme storms from those of past tsunamis. This study
contributes to this aim by investigating patterns of sedimentation
associated with extreme coastal flood events, in particular, within the Lagoa
de Óbidos (Portugal). The recent stratigraphy of this coastal lagoon was
studied using a wide range of techniques including visual description,
grain-size analysis, digital and x-ray photography, magnetic susceptibility
and geochemical analysis. The sequence was dated by 14C, 210Pb and
Optically Stimulated Luminescence. Results disclose a distinctive coarser
sedimentary unit, within the top of the sequence studied, and shown in
quartz sand by the enrichment of elements with marine affinity (e.g., Ca and
Na) and carbonates. The unit fines upwards and inland, thins inland and
presents a sharp erosive basal contact. A noticeable post-event change in
the sedimentary pattern was observed. The likely agent of sedimentation is
discussed here and the conceivable association with the Great Lisbon tsunami
of AD 1755 is debated, while a comparison is attempted with a possibly
synchronous deposit from a tsunami in Martinhal (Algarve, Portugal). The
possibility of a storm origin is also discussed in the context of the
storminess of the western Portuguese coast and the North Atlantic
Oscillation. This study highlights certain characteristics of the
sedimentology of the deposits that may have a value in the recognition of
extreme marine inundation signatures elsewhere in the world. |
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