High-resolution X-ray fluorescence core scanning analysis of Les Echets (France) sedimentary sequence: new insights from chemical proxies



The Les Echets sediment sequence has recently been the subject of a high-resolution, multi-proxy study which revealed shifts in lake productivity linked to Greenland stadials and interstadials over the last 40 ka (Wohlfarth et al., 2008. Rapid ecosystem response to abrupt climate changes during the last glacial period in western Europe, 40–16 ka. Geology36: 407–410). Here we present new elemental data for this sequence as acquired using an X-ray fluorescence core scanning system which provides in situ high-resolution, continuous, multi-element analyses. It was found that the strength of associations between the studied elements (Ti, Rb, K, Zr, Si, Ca, Sr, Mn and Fe) varied over time with changes in lake status which are ultimately driven by changes in climate. Increases in fine-grained, detrital input (as indicated by Ti, Rb, K and Zr/Rb) overlap with independently established periods of lower lake productivity and are interpreted to represent more arid conditions. Several of these arid periods are coincident with low diatom concentrations and the timing of Heinrich events H4, H3 and H2. The duration of the environmental impacts linked to the H events varied by proxy with elemental data (Ti and Zr/Rb) estimating shorter events than the diatom data. Periods of lower detrital input and coarser grain sizes agreed in time with periods of higher lake productivity. The elemental data provide new insights into hydrological changes and related sediment processes within the catchment, and highlight the need for multi-element and multi-proxy approaches when reconstructing climate change using lacustrine sediment sequences. Copyright © 2011 John Wiley & Sons, Ltd.