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

Abstract

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 . Rapid ecosystem response to abrupt climate changes during the last glacial period in western Europe, 40-16 ka. Geology 36: 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.

Hydroclimatic shifts in northeast Thailand during the last two millennia – the record of Lake Pa Kho

“…Selected elemental data (Si, K, and Ti) obtained from XRF scanning were averaged over 1 cm intervals and then normalized by (incoherent + coherent) scattering to remove various instrumental effects (Kylander et al, 2011). Si, K and Ti are here used as proxies for mineral input.…”

Natural and anthropogenic drivers of calcium depletion in a northern forest during the last millennium

“…To assess whether the decline in Ca could be due to dilution from an increase in the concentration of other sedimentary components, we compared Ca concentrations with titanium (Ti; Fig. 1B), which is an erosion proxy (19), and organic carbon percentage (%C; Fig. 1C), used as an organic matter proxy (20).…”

Condiciones ambientales a finales del Estadio Isotópico 6 (EI 6: > 130000 años) en el centro de México: caracterización de una sección de sedimentos laminados proveniente del Lago de Chalco

“…Las bandas amarillo pálido, en general, también tienen valores altos de esta relación. La relación Si/Ti es proporcional a la abundancia de sílice biogénico (Kylander et al, 2011) siendo las diatomeas y las esponjas de agua dulce los principales organismos silíceos en los lagos. El patrón observado, con valores Si/Ti altos en la lámina clara, es consistente con las observaciones al microscopio tanto óptico como electrónico, donde se identificó que estas láminas están formadas mayoritariamente por valvas de diatomeas (Figura 3c).…”

“…Siendo el Ti un indicador de elevada escorrentía y transporte de terrígenos de la cuenca hacia el lago (Kylander et al, 2011;Corella et al, 2012), se infiere que las láminas oscuras se depositaron en periodos de elevada precipitación y escorrentía superficial. Por otro lado, los altos valores de Si/Ti en las láminas claras y la gran abundancia de valvas de diatomeas permiten identificarlas como una facies biogénica de lodo (ooze) de diatomeas, si bien también se detecta la presencia de minerales autigénicos, lo que indica que el depósito de esta facies estuvo asociado con florecimientos estacionales de diatomeas durante los cuales la alta tasa de fotosíntesis favoreció la precipitación de estos minerales (Sáez et al, 2007).…”