Reconstruction of paleostorm events in a coastal lagoon (Herault, South of France)
Résumé
Finding records of past catastrophic storm events is essential to evaluate the long term climatic evolution in a given coastal area. This question has been addressed by the study of sediment cores sampled in a small coastal lagoon of the French Mediterranean coast (Pierre Blanche lagoon). Two cores were studied in detail and revealed the presence of three main storm events. The sedimentation rates calculated using the CFCS Pb-210 model, in agreement with Cs-137 data, are 3 +/- 0.4 and 4.2 +/- 0.7 mm y(-1) near the border and in the center of the lagoon respectively. This suggests that the 0.6 m deep lagoon could be filled with sediments over the next 150 yr. Our study shows that storm events can be characterized in sedimentary sequences identified by facies, grain size and faunal assemblages (lagoonal and marine species). Comparison of Pb-210, C-14 chronology and historical accounts suggest that the three identified storm events took place in 1742, 1839 and 1893 A.D. (i.e. about one catastrophic event per century).