Extreme events in the sedimentary record of maar Lake Pavin: Implications for natural hazards assessment in the French Massif Central

Abstract

A set of sedimentary cores, high resolution swath bathymetry and subbottom profiler data provides new insights on sedimentary processes in meromictic maar Lake Pavin, France.Three sedimentary environments (i.e., littoral, plateau and basin) have been identified in the lake from sediment composition using bulk organic geochemistry and the analysis of hydroacoustic images. Various forms of rapidly deposited layers (RDLs) have been identified and radiocarbon dated. An up to date stratigraphy of sedimentary events matching coeval RDLs across the lake is presented and illustrates a wide range of natural hazards linked to Lake Pavin during the last 2,000 years. In AD 600, a sudden lake outburst triggered a slump deposit along with a 9 m lake-level drop that drove shifts in sedimentary organic matter composition. Outside the lake, outburst flood deposits have been described downstream and provide sedimentary evidence for this event. The lake-level drop also favored the generation of gravity reworking phenomena, as shown by (1) a regional earthquake-triggered large slope failure on the plateau connected to a mass-wasting deposit in the basin dated to AD 1300, and (2) a succession of turbidites in AD 1825 and AD 1860 contemporaneous to two historic earthquakes, suggesting that this lake is sensitive to earthquakes with a minimum epicentral intensity of V. Finally, past observations of lake water color changes in AD 1783 and AD 1936, similar to reports in other meromictic lakes, match iron-rich deposits identified in maar lake sediments and suggest that Lake Pavin could have undergone limnic eruptions.

Historical seismicity of the Mont Dore volcanic province (Auvergne, France) unraveled by a regional lacustrine investigation: New insights about lake sensitivity to earthquakes

“…This region hosts various types of small volcanogenic lakes which are, with rare exceptions, barely known in limnogeological terms. Supporting pioneer works published by Chapron et al (2012), the present study provides an up-to-date dataset of high-resolution seismic profiles coupled to radiocarbon-dated sediment cores from four nearby lakes (100 km 2 area), including maar Lake Pavin (Schettler et al, 2007;Chapron et al, 2010Chapron et al, , 2012Chassiot et al, 2016), maar Lake Chauvet (Juvigné, 1992), volcanic-dam Lake Montcineyre (Chapron et al, 2012) and the poorly documented glacial Lake Guéry (Fig. 1).…”

“…Core-to-core correlation is supported by the large uncertainties obtained from calibrated ages sampled in core PAV12 (Fig. 4, Table 2), as described in Chassiot et al (2016). In Lake Chauvet, the top-core CHA13-7B does not contain any organic remains.…”

“…1). This regional dataset also improve the scope of earthquakes that triggered turbidites recently described in Lake Pavin sedimentary archives (Chassiot et al, 2016).…”

“…and (3) a large slope failure around AD 1300 and recurrent turbidites in the XIX th century (Chassiot et al, 2016) (Fig. 3).…”

“…The morphology of Lake Pavin was in addition investigated using a Reson Seabeat 8101 multibeam echosounder allowing us to generate a high-resolution (50 cm × 50 cm) bathymetric map ( Fig. 3) (Chapron et al, 2010;Chassiot et al, 2016). For the other lakes, a total of 12 km of seismic lines with a maximal spacing of 200 m (lakes Chauvet and Montcineyre) and 100 m (Lake Guéry) were gathered in the SEG-Y format using IHS The Kingdom Suite™ software.…”