The Rabat and Larache boulder fields; new examples of high-energy deposits related to storms and tsunami waves in north-western Morocco |
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| Authors: | F Medina N Mhammdi A Chiguer M Akil E B Jaaidi |
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| Institution: | 1.Institut Scientifique, Département des Sciences de la Terre, Laboratoire de Géologie et Télédetection (associé CNRST URAC 46), Equipe Télédétection, Ressources et Risques naturels,Université Mohammed V-Agdal,Rabat,Morocco;2.Université Mohammed V-Agdal, Institut Scientifique, Laboratoire de Physique du Globe,Rabat,Morocco;3.Faculté des Sciences, Département de Géologie,Université Mohammed V-Agdal,Rabat,Morocco |
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| Abstract: | The coastal areas of south-west Iberia and north-west Morocco host numerous megaclast accumulations thought to have been emplaced
by high-energy waves, namely by the major tsunami related to the 1 November 1755 AD earthquake. New observations were carried
out along several transects from Rabat and Larache areas, using statistical methods applied to boulder size. The main results
are (a) the boulders belong to two or three sources located within the Pleistocene–Holocene formations of both areas, but
only from a single source at Harhoura; (b) the boulders in Larache are generally small, thin and show a normal polarity, whereas
those of Rabat are much larger and are often overturned; (c) the directions of inclination of imbricate boulders are variable
at Rabat (N, NW and W), whereas they are constant in Larache (WNW); (d) the blocks were displaced for distances up to 150 m
in Rabat, while the displacement of the Larache boulders was stopped by the MHW cliff; (e) the hydrodynamic equations suggest
that tsunami waves, with maximum amplitudes of 5–11 m in Rabat and 4.5 m in Larache, were responsible for the displacement
of the largest boulders, whereas storms may have displaced smaller ones. |
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