The Lesser Antilles are a densely populated region where local populations and industrial facilities are concentrated at the coastlines, and are therefore exposed to many rapid-onset hazards such as ...hurricanes and tsunamis. However, the historical catalog of these events is too short to allow risk assessment and return period estimations, and it needs to be completed with long-term records of washover deposits in coastal sedimentary environments such as lagoons. In this study, two sediment cores were taken in March 2018 in a small coastal lagoon on Scrub Island (northeastern Caribbean). Sedimentological, geochemical, microfaunal and chronological analyses enabled us to identify 25 sandy layers resulting from high-energy-marine floods. Two of these layers were interpreted as tsunami deposits based on sedimentological (rip-up clast of the underlying cohesive substrate and internal mud laminae), and geochemical evidence. The most recent deposit is associated with the transatlantic tsunami triggered by the 1755 CE Lisbon earthquake. The older one is the thickest sandy layer recorded in the lagoon, with an age range of 1364–1469 cal. CE, as determined using 14C dating. This event was recorded in sedimentary archives of both the northern and the southern part of the Caribbean, with its large spatial extent, supporting a distant tsunamigenic origin. The 23 remaining sandy layers were interpreted as storm deposits, based on sedimentological and chronological data, with the three most recent layers being correlated with historical hurricanes. This new 1600 year-long record displays similarities with that of the Bahamas, with the periods of intense hurricane activity being in antiphase with those of the north-eastern US coast. This regional comparison may provide evidence for a latitudinal forcing of hurricane tracks through time in relation to climate fluctuations.
No megathrust earthquake similar to the Magnitude class 9 events in Sumatra in 2004 or in Japan in 2011 was firmly reported at the Lesser Antilles subduction zone. The largest known tsunamis followed ...either a strong intraplate earthquake (1867, Virgin Islands) or were transoceanic due to the 1755 Lisbon earthquake. In this region, where the convergence rate between the American and Caribbean plate is low, the recurrence time of large earthquakes may be long (several centuries or millennia) and the historical record of such events is short. It is thus difficult to estimate their impact and becomes crucial to gain information from longer-term geological records and tsunami modeling. An increasing number of old prehistoric tsunami deposits have been identified in recent years on several islands in the northern segment of the Lesser Antilles arc, between Antigua and Puerto-Rico, in Anegada, St-Thomas (Virgin Islands), Anguilla and Scrub islands. Here, we carefully review all those studies and evidenced that most tsunami deposits are about 500 to 800 years old (1200 to 1500 cal yrs. CE) likely suggesting a large event or a cluster of events at that time. We combined information provided by the sedimentological records (distribution and altitude of the sediment deposits) and tsunami models to discuss the origin of the middle age Pre-Colombian event(s). We listed all faults as possible sources of tsunamis in this complex tectonic region. We performed 35 run-up models by using high-resolution/topographic grids to compare the simulated wave heights and run-up distance to the sediment record. We showed that few models are able to generate tsunami waves which heights and run-up distances match the characteristic of the observed tsunami deposits. These models are Magnitude class 9 M-thrust earthquakes rupturing the subduction interface between 30 km in depth to the trench facing Anegada Island. Magnitude class 8 outer-rise earthquakes, modeled along the trench, are other candidates for the Pre-Columbian event(s) although less convincing than the mega-thrust ones. The realism of these models is discussed in the light of the recent coupling models of the subduction zone based on short-term geodetic records. Finally, considering all the results and data, the equally strong hypothesis that these sediments were deposited by one or several storms remains less convincing than our tsunamigenic earthquakes scenarios. We conclude that the occurrence of one or several large megathrust or outer-rise earthquakes in association with damaging tsunamis likely have occurred in the past in the Lesser Antilles and could occur again in the future. This opens the discussion on the threat posed by such catastrophic event in these densely populated and touristic regions.
La revue Mondes en développement fête ses cinquante ans. Une analyse lexicale permet de brosser le tableau de son évolution. F. Perroux a fondé la revue et demeure l’un des plus gros contributeurs ...aux côtés de R. Gendarme, H. Gérardin ou encore Ph. Hugon. L’Afrique reste la zone d’étude privilégiée par les auteurs. Le développement durable s’invite dans les sommaires des années 2000, et les « pays émergents » remplacent de plus en plus souvent les « pays en voie de développement ». 200 numéros plus tard, Mondes en développement reste fidèle à son projet originel : une revue francophone pluraliste sur le développement. Classification JEL : A3, O1, Y1
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