GEOCHEMICAL LANDSCAPES OF ALASKA

An ultra-low density (approximately 1 sample/6,000 km2) statewide geochemical data set for 265 samples of soils and other unconsolidated surficial materials is here reanalyzed and reinterpreted. Smoothed and interpolated geochemical distribution patterns are evaluated relative to bedrock type and ecosystem parameters. Mapped patterns include K, U, and Th which show elevated concentrations near the granitic plutons of the Yukon-Tanana Upland and the Seward Peninsula. In addition, the pattern for Ba shows relatively high concentrations in soils of the interior that roughly correspond to flysch basins whose turbidite sources are lower Cretaceous and Jurassic marine sedimentary rocks. A 5-division ecoregion classification system and principal components (PC) analysis are used to evaluate chemical weathering and to examine relations among climate (mean annual temperature and precipitation) and soil properties (chemistry, pH, and organic matter). PC analysis of these climatic parameters and soil major cation chemistry resulted in 5 factors that explain 77 percent of the total variance in the data. The factors were identified as (1) clay or reactive oxides, (2) latitude, (3) soil organic matter, (4) carbonate and soil ion exchange, and (5) soil potassium feldspar. These types of data and PC analysis are proving useful in assessing geochemical baselines and in interpreting broad regional geochemical landscape patterns.