A high-resolution record of paleostorm events along the French Mediterranean coast over the past 7000 years was established from a lagoonal sediment core in the Gulf of Lions. Integrating grain size, faunal analysis, clay mineralogy and geochemistry data with a chronology derived from radiocarbon dating, we recorded seven periods of increased storm activity at 6300–6100, 5650–5400, 4400–4050, 3650–3200, 2800–2600, 1950–1400 and 400–50 cal yr BP (in the Little Ice Age). In contrast, our results show that the Medieval Climate Anomaly (1150–650 cal yr BP) was characterised by low storm activity.The evidence for high storm activity in the NW Mediterranean Sea is in agreement with the changes in coastal hydrodynamics observed over the Eastern North Atlantic and seems to correspond to Holocene cooling in the North Atlantic. Periods of low SSTs there may have led to a stronger meridional temperature gradient and a southward migration of the westerlies. We hypothesise that the increase in storm activity during Holocene cold events over the North Atlantic and Mediterranean regions was probably due to an increase in the thermal gradient that led to an enhanced lower tropospheric baroclinicity over a large Central Atlantic-European domain.

Event deposits in lake sediments provide invaluable chronicles of geodynamic and climatic natural hazards on multi-millennial timescales. Sediment archives are particularly useful for reconstructing high-impact, low-frequency events, which are rarely observed in instrumental or historical data. However, attributing a trigger mechanism to event deposits observed in lake sediments can be particularly challenging as different types of events can produce deposits with very similar lithological characteristics, such as turbidites. In this review paper, we summarize the state of the art on event deposits in paleolimnology. We start by describing the sedimentary facies typical of floods, glacial lake outburst floods, avalanches, hurricanes, earthquakes, tsunamis, volcanic eruptions, and spontaneous delta collapses. We then describe the most indicative methods that can be applied at the scale of lake basins (geophysical survey, multiple coring) and on sediment cores (sedimentology, inorganic and organic geochemistry, biotic approach). Finally, we provide recommendations on how to obtain accurate chronologies on sediment cores containing event deposits, and ultimately date the events. Accurately identifying and dating event deposits has the potential to improve hazard assessments, particularly in terms of the return periods, recurrence patterns, and maximum magnitudes, which is one of the main geological challenges for sustainable worldwide development.

Over the last decade, an increasing number of studies have used lake sediment DNA to trace past landscape changes, agricultural activities or human presence. However, the processes responsible for lake sediment formation and sediment properties might affect DNA records via taphonomic and analytical processes. It is crucial to understand these processes to ensure reliable interpretations for “palaeo” studies. Here, we combined plant and mammal DNA metabarcoding analyses with sedimentological and geochemical analyses from three lake-catchment systems that are characterised by different erosion dynamics. The new insights derived from this approach elucidate and assess issues relating to DNA sources and transfer processes. The sources of eroded materials strongly affect the “catchment-DNA” concentration in the sediments. For instance, erosion of upper organic and organo-mineral soil horizons provides a higher amount of plant DNA in lake sediments than deep horizons, bare soils or glacial flours. Moreover, high erosion rates, along with a well-developed hydrographic network, are proposed as factors positively affecting the representation of the catchment flora. The development of open and agricultural landscapes, which favour the erosion, could thus bias the reconstructed landscape trajectory but help the record of these human activities. Regarding domestic animals, pastoral practices and animal behaviour might affect their DNA record because they control the type of source of DNA (“point” vs. “diffuse”).

Significance: A record of lake sediment spanning approximately 100 years allowed us to reconstruct the long-term succession of herbicide, fungicide, and insecticide treatments in a vineyard catchment in France. This record of pesticide deposition is consistent with the historical onset and banning of these chemical substances by French and European environmental agencies. We also present evidence of the effects of postemergence herbicides, such as glyphosate, on soil erosion and evidence of the release of banned remnant pesticides, such as dichlorodiphenyltrichloroethane (DDT), that are stored in vineyard soil back into the environment. These results indicate that the sink–source dynamics of pesticides, which are crucial in ecotoxicological risk assessment, should take into account the effects of a changing environment on pesticide storage.