Geochemical characterization of soil organic matter and variability of a postglacial detrital organic supply (chaillexon lake, france)

Abstract

Geochemical analysis of sedimentary organic matter in recent lacustrine sediments appears to be a useful tool in providing information concerning past environmental conditions. However, such analysis is often made without knowing the geochemical characteristics of the organic matter derived from the watershed and, more explicitly, its soils. The present work deals with (i) a geochemical investigation (Rock-Eval pyrolysis) of soil organic matter sampled in a lake watershed, and (ii) the study of the sedimentary organic matter trapped in the lake deposits. The research was conducted on Chaillexon Lake which was created by a rock collapse that dammed the palaeovalley of the Doubs River about 12 000 years ago. Since this event, the sediment trap provides a continuous palaeoclimatic record for the Postglacial period.Results obtained lead to two main conclusions. First, the variability of Rock-Eval pyrolysis values observed in soils modifies the common interpretation given to these parameters in the characterization of sedimentary organic matter. Indeed, variations in these parameters point not only to varying proportions of terrestrial and lacustrine organic matter in a lacustrine infilling but also to variations of the terrestrial supply linked with the evolution of vegetal cover in the catchment. The second conclusion is that the story of the Chaillexon lacustrine system is marked by a rather sudden soil and forest development at the Preboreal-Boreal transition (9000 BP).

Guidelines for Rock–Eval analysis of recent marine sediments

“…It has been increasingly applied to the characterization of organic matter (OM) in soils (Di Giovanni et al, 2000;Disnar et al, 2003;Hetényi et al, 2005;Sebag et al, 2006;Graz et al, 2012;Saenger et al, 2013;Hétényi and Nyilas, 2014), the detection of black carbon (Copard et al, 2006;Poot et al, 2009) and even the analysis of pure organic products (Carrie et al, 2012). It has also been applied for several decades to the study of recent lacustrine sediments (Campy et al, 1994;Di Giovanni et al, 1998;Meyers and Lallier-Vergès, 1999;Ariztegui et al, 2001;Steinmann et al, 2003;Sanei et al, 2005;Jacob et al, 2004;Boussafir et al, 2012;Zocatelli et al, 2012;Lavrieux et al, 2013;Sebag et al, 2013, amongst others) or recent marine sediments (Peters and Simoneit, 1982;Hussain and Warren, 1991;Calvert et al, 1992;Combourieu et al, 1999;Ganeshram et al, 1999;Ozcelik and Altunsoy, 2000;Holtvoeth et al, 2001Holtvoeth et al, , 2003Holtvoeth et al, , 2005Tamburini et al, 2003;Baudin et al, 2007Baudin et al, , 2010Kim et al, 2007;Marchand et al, 2008;Tribovillard et al, 2008Tribovillard et al, , 2009Biscara et al, 2011;…”

Mass-movement and flood-induced deposits in Lake Ledro, southern Alps, Italy: implications for Holocene palaeohydrology and natural hazards

“…RE parameters such as the total organic carbon (TOC, %), the S2 (i.e. the amount of hydrocarbon that escapes from the sample during the thermal cracking, expressed in mgHC) and the thermal maturity (Tpeak, • C) measurements can be used to characterize soil organic matter (Di Giovanni et al, 1998;Sebag et al, 2005;Copard et al, 2006) and to discriminate between an aquatic or terrestrial origin of the organic matter into lacustrine environments (Talbot and Livingstone, 1989;Simonneau et al, 2013). S2 represents the total amount of hydrocarbon that escapes from the sample during the thermal cracking (Ariztegui et al, 2001).…”

“…5c) and opaque particles without high reflectance; and (2) pollen microfossil particles composed of spores and pollens. The rAP and the LCF identified in this study are similar to those described by Di Giovanni et al (1998), Graz et al (2010) or Simonneau et al (2013) and associated with soil particles (rAP) and upper vegetation debris (LCF) coming both from the watershed. Variations in the values of the rAP/LCF ratio can be used to disentangle the impact of land use and climate during the Holocene on the vegetal cover, soil erosion and sediment load of rivers in Alpine environments (cf.…”

Tracking Holocene glacial and high-altitude alpine environments fluctuations from minerogenic and organic markers in proglacial lake sediments (Lake Blanc Huez, Western French Alps)

“…Generally, the isolated OM fraction is obtained after the elimination of carbonate and silicate phases by hydrochloric and hydrofluoric acids attacks. This method allows to identify and quantify the major organic constituents (Di Giovanni et al, 1998Noël et al, 2001;Sebag et al, 2006;Simonneau et al, 2013aSimonneau et al, , 2013bSimonneau et al, , 2013c Combaz (1964) and is based on the incorporation of a known mass of a standard (Cupressus pollen) in organic concentrate after acid attacks. QOP allows the quantification of organic material inputs into modern environments in mass per gram of sample.…”