This Article Full Text (PDF) References Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Add to Saved Citations Download to citation manager Request Permissions Request Reprints Add to My Marked Citations Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Ewing, H. A. Articles by Nater, E. A. Search for Related Content GeoRef GeoRef Citation Social Bookmarking                   What's this?

Use of scanning electron microscopy to investigate records of soil weathering preserved in lake sediment

Department of Ecology, Evolution, and Behavior, University of Minnesota, 1987 Upper Buford Circle, St Paul, MN 55108, USA; Institute of Ecosystem Studies, Box AB, Millbrook, NY 12545, USA, ewingh{at}ecostudies.org

Edward A. Nater

Department of Soil, Water, and Climate, University of Minnesota, 1991 Upper Buford Circle, St Paul, MN 55108, USA

Reconstruction of soil weathering is one of the more difficult problems for palaeoecologists interested in landscape-scale environmental changes. Here we use scanning electron microscopy and energy dispersive x-ray analysis (SEM/EDS) to study the pitting of feldspars in soils and lake sediments at two sites in the Great Lakes region, USA. A semi-quantitative feldspar weathering index (FWI) allows description of the weathering status for large numbers of individual grains, and reveals differences among soil horizons and strata of lake sediment as well as between the two sites. Feldspars in upper soil horizons generally have greater FWI than those in lower horizons, but analyses also suggest considerable weathering in the soil C horizon at the site with more rapid water infiltration. At one site, the FWI of upper soil horizons and surface lake sediment are similar, implying that lake sediments have the potential to record changes in soil over time. However, differ ences between upper soil horizons and surface sediment at the other site highlight the need to examine more sites and more profiles within sites to better relate catchment and sediment characteristics. We interpret increases in the FWI over time within lake sediments as evidence of progressive weathering of soils and conclude that the sites had different histories of soil development. However, the complexities of sediment deposition in lakes and the paucity of information relating FWI to soil characteristics prevent straightforward reconstruction of soil development. Variability within each record appears tied to initial grain chemistry, depo sitional environment, changes in lake level and progressive degradation of grains. As more information relating micromorphology to soil characteristics becomes available, this technique should become a more useful complement to chemical studies of lake sediment.

Key Words: Soil development • lake sediment • soil weathering • weathering index • feldspars • palaeoecology • scanning electron microscopy • energy dispersive x-ray spectroscopy • SEM/EDS • Holocene

CiteULike    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?