Flood and earthquake disturbance of ²¹⁰Pb geochronology (Lake Anterne, NW Alps)

Abstract

Dating recent lake sediment records yielding disturbed 210Pb profiles has been a problem of wide interest in palaeoclimatic and palaeoseismic studies over the last few centuries. When applied to an alpine lake sedimentary record, a high‐resolution sedimentological study reveals that the 210Pb profile is disturbed by the occurrence of single‐event deposits triggered by two different mechanisms: flood events deposits and gravity reworking. Removing disturbed layers from the 210Pb profile yields a logarithmic depth–activity relationship. Using a simple 210Pb decay model (CFCS) provides an assessment of mean accumulation rate of `continuous sedimentation', as opposed to `event‐linked sedimentation'. The correlation of the thickest four gravity‐reworked deposits with historically known earthquakes permits both validation and refinement of the age–depth relationship. This refinement highlights variations in accumulation rate consistent with post‐Little Ice Age climatic variations.

A multi-centennial record of past floods and earthquakes in Valle d'Aosta, Mediterranean Italian Alps

“…formation of concentrated density flows of suspended sediments during a subaquatic mass movement (e.g. Mulder and Cochonnat, 1996;Arnaud et al, 2002;Wilhelm et al, 2016b). The HB characteristics are very similar to deposits previously described by many studies (e.g.…”

“…5). We excluded 210 Pbex values associated with these instantaneous deposits to construct a synthetic sediment record (Arnaud et al, 2002). The CFCS model (Goldberg, 1963) was applied to the synthetic 210 Pbex profile and indicates that the sequence is characterized by two periods of different sedimentation rates.…”

“…GBs are associated with turbidity currents triggered by either flood events or mass movements (e.g. Sturm and Matter, 1978;Shiki et al, 2000;Arnaud et al, 2002;Mulder and Chapron, 2011;Wilhelm et al, 2012b). In the latter case, they are formed by the sediment that is transported in suspension during the mass movement and then deposited over the mass-wasting deposits and/or further in the lake basin (e.g.…”

Long livestock farming history and human landscape shaping revealed by lake sediment DNA

“…Visual identification was based on the sedimentological features of these deposits. These features are characterized by the succession of three phases that become finer upward 36,41 from bottom to top as follows: coarse and well-sorted sediments; a mixture of silts and fine sands; and a layer of fine silts and clays. The thickness of these erosive deposits varies from 0.5 to 27 cm.…”

Identifying sediment discontinuities and solving dating puzzles using monitoring and palaeolimnological records

“…In turn, information on sedimentation processes may allow for inferences of key environment changes in the past, e.g. floods, earthquakes, fire, or human reclamation events (Arnaud et al, 2002;Moreno et al, 2008) and although sediment disturbances can be disadvantageous, numerous palaeolimnological studies have revealed that a reasonable chronology can be achieved, especially where multicore comparisons allow sediment disturbances to be distinguished (Tibby 2001;Donovan and Grimm, 2007;Morellón et al, 2011).…”