Normalizing XRF-scanner data: A cautionary note on the interpretation of high-resolution records from organic-rich lakes

X-ray fluorescence (XRF) scanning of unlithified, untreated sediment cores is becoming an increasingly common method used to obtain paleoproxy data from lake records. XRF-scanning is fast and delivers high-resolution records of relative variations in the elemental composition of the sediment. However, lake sediments display extreme variations in their organic matter content, which can vary from just a few percent to well over 50%. As XRF scanners are largely insensitive to organic material in the sediment, increasing levels of organic material effectively dilute those components that can be measured, such as the lithogenic material (the closed-sum effect). Consequently, in sediments with large variations in organic material, the measured variations in an element will to a large extent mirror the changes in organic material. It is therefore necessary to normalize the elements in the lithogenic component of the sediment against a conservative element to allow changes in the input of the elements to be addressed. In this study we show that Al, which is the lightest element that can be measured using the Itrax XRF-scanner, can be used to effectively normalize the elements of the lithogenic fraction of the sediment against variations in organic content. We also show that care must be taken when choosing resolution and exposure time to ensure optimal output from the measurements.

[1]  M. Haschke.  The Eagle III BKA system, a novel sediment core X-ray fluorescence analyser with very high spatial resolution , 2006, Geological Society, London, Special Publications.

[2]  B. Stewart,et al.  Assessment Methods for Soil Carbon , 2000 .

[3]  M. Saier,et al.  Climate Change, 2007 , 2007 .

[4]  G. Haug,et al.  Influence of the intertropical convergence zone on the East Asian monsoon , 2007, Nature.

[5]  H. Brumsack,et al.  Geochemical characteristics of deep-sea sediments from the Arabian Sea: a high-resolution study , 2000 .

[6]  H. Brumsack.  The trace metal content of recent organic carbon-rich sediments; implications for Cretaceous black shale formation , 2006 .

[7]  H. Chen,et al.  Hydrothermal alteration of andesite in acid solutions: Experimental study in 0.05 M H2SO4 solution at 110 °C , 2003 .

[8]  G. Weltje,et al.  Calibration of XRF core scanners for quantitative geochemical logging of sediment cores: Theory and application , 2008 .

[9]  H. Brumsack,et al.  Cyclic variations in the chemical composition of eastern Mediterranean Pliocene sediments: a key for understanding sapropel formation , 1999 .

[10]  Tien-Nan Yang,et al.  Late Holocene paleoenvironmental changes in subtropical Taiwan inferred from pollen and diatoms in lake sediments , 2009 .

[11]  M. Kölling,et al.  Influence of the water content on X‐ray fluorescence core‐scanning measurements in soft marine sediments , 2007 .

[12]  C. Chen,et al.  Holocene East Asian monsoon variability: Links to solar and tropical Pacific forcing , 2006 .

[13]  T. L. Lyon,et al.  The Nature and Properties of Soils , 1930 .

[14]  L. Löwemark,et al.  Arctic Ocean manganese contents and sediment colour cycles , 2008 .

[15]  R. Rudnick,et al.  Nature and composition of the continental crust: A lower crustal perspective , 1995 .

[16]  T. V. van Weering,et al.  The Avaatech XRF Core Scanner: technical description and applications to NE Atlantic sediments , 2006, Geological Society, London, Special Publications.

[17]  K. Aoike,et al.  Non-Destructive X-Ray Fluorescence (XRF) Core-Imaging Scanner, TATSCAN-F2 , 2006 .

[18]  H. Rollinson.  Using Geochemical Data: Evaluation, Presentation, Interpretation , 1993 .

[19]  K. Wei,et al.  Detrital sediment supply in the southern Okinawa Trough and its relation to sea-level and Kuroshio dynamics during the late Quaternary , 2008 .

[20]  R. Rothwell,et al.  New techniques in sediment core analysis: an introduction , 2006, Geological Society, London, Special Publications.

[21]  H. Sanei,et al.  Historical variation of elements with respect to different geochemical fractions in recent sediments from Pigeon Lake, Alberta, Canada. , 2001, Journal of environmental monitoring : JEM.

[22]  Eugene P. Bertin,et al.  Principles and Practice of X-Ray Spectrometric Analysis , 1970 .

[23]  B. Stewart,et al.  Estimation of Particulate and Total Organic Matter by Weight Loss-on-Ignition , 2000 .

[24]  A. Maxwell.  Holocene Monsoon Changes Inferred from Lake Sediment Pollen and Carbonate Records, Northeastern Cambodia , 2001, Quaternary Research.

[25]  R. G. Rothwell.  New Techniques in Sediment Core Analysis , 2006 .

[26]  T. Lyons,et al.  Trace metals as paleoredox and paleoproductivity proxies: An update , 2006 .

[27]  R. G. Rothwell,et al.  ITRAX: description and evaluation of a new multi-function X-ray core scanner , 2006, Geological Society, London, Special Publications.

[28]  S. Calvert.  Geochemistry of Pleistocene sapropels and associated sediments from the Eastern Mediterranean , 1983 .

[29]  Yue‐Gau Chen,et al.  Environmental Change in the Southwestern Coastal Plain of Taiwan since Late Pleistocene: Using Multiple Proxies of Sedimentary Organic Matter , 2005 .

[30]  B. Kanngießer,et al.  Handbook of practical X-ray fluorescence analysis , 2006 .

[31]  O. Magand,et al.  High-altitude varve records of abrupt environmental changes and mining activity over the last 4000 years in the Western French Alps (Lake Bramant, Grandes Rousses Massif) , 2007 .

[32]  Climate and the Collapse of Maya Civilization , 2003, Science.

[33]  E. Bard,et al.  Toward direct, micron‐scale XRF elemental maps and quantitative profiles of wet marine sediments , 2007 .

[34]  R. Tyson.  Sedimentary Organic Matter , 1995 .