The Lesser Antilles are a densely populated and a very touristic region exposed to many short-term 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 geological records. Two sediment cores were sampled in March 2018 in a small coastal lagoon on Scrub Island (north eastern Caribbean). Here, we present sedimentological, geochemical, microfaunal and chronological analyses that 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 and geochemical evidence. The most recent deposit is associated with the transatlantic tsunami triggered by the 1755 AD Lisbon earthquake. The older is the thickest sandy layer recorded in the lagoon and is dated at 1415 cal. AD (1364-1469 cal. AD). This event was recorded in both the northern and the southern part of the Caribbean, with its large extent supporting a tsunamigenic origin. The 23 remaining sandy This is a non-peer reviewed preprint submitted to EarthArXiv The manuscript is under review at Sedimentary Geology 2 layers were interpreted as resulting from hurricanes, with the three most recent layers being associated with historical hurricanes. This new 1600 year-long reconstructed chronicle, has been compared to other published hurricane chronicles from the region. Scrub chronicle is the most eastern site and displays similarities with that of the Bahamas, while it is in antiphase with that of the north eastern US coast. This regional comparison may provide evidence of a latitudinal forcing for the hurricane tracks through time in relation to climate fluctuations.
a b s t r a c tUnderstanding estuarine sediment dynamics and particularly turbidity maximum dynamics is crucial for the management of these coastal systems. Various processes impact the formation, movement and structure of the turbidity maximum. Several studies have shown that tidal asymmetry and density gradients are responsible for the presence of this suspended sedimentary mass.The Charente estuary is a highly turbid system (with suspended sediment concentrations often in excess of 5 g/L) that remains poorly understood despite its strong impact on local activities. In this study, a three-dimensional hydrosedimentary model is developed to represent the sediment dynamics of this estuary. Model validation demonstrates good accuracy, especially on reproducing semi-diurnal and spring-neap variability. Several simulations are performed to evaluate the influence of tides and river discharge on the turbidity maximum. Mean and maximum suspended sediment concentrations (SSC) and sediment stratification are calculated. SSC transects are also used to visualize the suspended sediment distribution along the estuary.The turbidity maximum generally oscillates between the river mouth and the Rochefort area (20 e30 km upstream). The model shows strong variations at different time scales, and demonstrates that SSC is mainly driven by deposition/resuspension processes. Spring-neap comparisons show that the turbidity maximum is not well-defined during neap tides for low and mean runoff conditions. Simulations of spring tides and/or high runoff conditions all result in a compact suspended sedimentary mass.Performing simulations without taking density gradients into account demonstrates that tidal asymmetry is the main mechanism leading to the formation of the turbidity maximum. However, density gradients contribute to maintaining the stability of the turbidity maximum. Vertical stratification traps sediments at the bottom. Longitudinal stratification ensures a sharper edge at the downstream limit of the suspended sedimentary mass, preventing a massive export of sediments.
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