Scanning Micro-X-Ray Fluorescence Elemental Mapping: A New Tool for the Study of Laminated Sediment Records

Shanahan, T.M., J.T. Overpeck, J.B. Hubeny, J. King, F.S. Hu, K. Hughen, G. Miller, and J. Black

2008 Geochemistry, Geophysics, Geosystems 9: 10.1029/2007GC001800



ABSTRACT

The utility of elemental mapping by scanning X-ray fluorescence (XRF) in the study of annual laminated sedimentary records was investigated on eight annually laminated sediment types. The examples were chosen to illustrate the potential of this approach in environments dominated by terrigenous, biological and chemical deposition. Individual laminae were identifiable in elemental maps of all sediment types and were enhanced through the use of data reduction techniques (e.g., principal components transformation). Laminae were least apparent in clastic dominated systems with no seasonal changes in sediment sources. In biologically dominated systems, element maps provided insights into the composition of the varve subcomponents, related to alternating terrigenous and biologically dominated seasonal periods of deposition. Chemically precipitated structures were more prevalent than expected from visual investigations alone and may provide an underutilized paleoenvironmental signature of changing limnological conditions. Elemental mapping offers a valuable tool for the study of laminated records that complements existing techniques (e.g., SEM, digital image analysis).