Chemical stratigraphy data analyses from lake sediments to characterize sudden or gradual environmental changes
by
Ramon Julià
Instituto de Ciencias de la Tierra (Jaume Almera), CSIC.
Coauthors: José-Antonio Luque

Lacustrine sediment records are powerful sensors of environmental history. Changes in land use, climate, volcanic activity, earthquakes (among others) have been deduced from proxy data analyses such as diatoms, pollen, ostracods, elemental analysis, stable isotopes, etc. Human impact on the biosphere and the response of human society to environmental changes have been recorded in these lacustrine sediments. Nevertheless, many interpretation tools are needed to produce convincing arguments for deciphering these changes. Data intercalibration and comparison are the most frequent tools because of the difficulty in quantifying some proxy data. In these cases, the results are only based on proxy data matching trends and analogs.

High resolution mineralogy (based on RX analyses) and elemental composition (based on ICPS analyses) of lacustrine sediments have been used to identify anthropogenic pollutants, flash floods, rockslide-avalanches, earthquakes, volcanic ash chronostratigraphy, and to document soil erosion or vegetation changes. Few papers discuss the problem of the timing of environmental change and the identification of catastrophic events, short events, or gradual environmental changes. High resolution chemical quantitative analyses of lacustrine sediments (in time windows of 10 to 20 years) provide a consistent approach to the characterization of environmental changes. Multivariate analyses such as canonical corresponfence analysis and/or principal component analysis (factor analyses) provide an useful tool to characterize the environmental changes and its propagation time scale. This last approach requires a consistent chronological model.

Examples of flash floods, short events and large scale environmental changes from Spanish lacustrine sequences and proxy-data processing will be discussed.

Date received: February 7, 2005

Copyright © 2005 by the author(s). The author(s) of this document and the organizers of the conference have granted their consent to include this abstract in Atlas Conferences Inc. Document # caod-73.