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Professional Paper 1716
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Geochemical Landscapes of Alaska—New Map Presentations and Interpretations for 23 Elements in Surficial Materials

By L.P. Gough, Bronwen Wang, D.B. Smith, and Nils Gustavsson

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Geochemical patterns are presented for 23 elements, ash yield, and pH in soils and other unconsolidated surficial materials from 265 collection sites throughout Alaska. This is a new presentation of data originally published in 1988 and released now with additional interpretation based on landscape geochemical principles (such as the effects of regional soils groups, climate, and vegetation) that influence observed areal patterns. The additional interpretations are applied to subjects involving ecosystems and soil-forming processes in cold climates, and the effects of parent material on observed patterns. Mean concentrations of most elements, in this ultra-low-density sampling of surficial materials from the State of Alaska, correspond well with those reported in similar materials from the conterminous United States. The utility of low-density geochemical sampling in the interpretation of landscape geochemical patterns and of ecosystem processes is demonstrated by (1) showing interpretable relations among physical and chemical parameters (for example, latitude, elevation, temperature, and geochemistry), and (2) comparing our surficial material data with a much larger, published stream sediment geochemical data set. A five-division ecoregion classification system is used to evaluate feldspar chemical weathering processes and to examine relations among climate (mean annual temperature and precipitation) and soil properties (chemistry, pH, and organic matter). Principal components analysis of these climatic and soil properties resulted in five factors that explain 77 percent of the total variance in the data. The factors were identified as (1) clay or reactive oxides, (2) physiographic or latitude, (3) soil organic matter, (4) carbonate and soil ion exchange, and (5) soil potassium feldspar. These data should prove useful in assessing geochemical baselines and in the interpretation of geochemical landscapes when the purpose is to identify broad regional patterns associated with surficial geology, mineral resource provinces, and geochemical areas of interest in human, animal, and plant health issues.

Version 1.0

Posted December 2005

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