Geochemical and Geophysical Characteristics of the Conterminous U.S.

This dataset is a collection of 12 rasters depicting geochemical and geophysical characteristics of surface or near surface geology. These rasters were created to quantify the influence of geology on surface and critical zone processes like stream water chemistry, soil formation, ecologic processes, and species distributions by providing estimates of spatial variability in current geochemical and geophysical conditions. Ten rasters are of lithological geochemistry depicting whole rock percent Al2O3, CaO, Fe2O3, K2O, MgO, N, Na2O, P2O5, S, and SiO2. Two rasters are of the lithological geophysical properties uniaxial compressive strength (MPa) and hydraulic conductivity (m/s). We derived these rasters by combining state geologic maps (Preliminary Integrated Geologic Map Databases for the United States, Open File Reports 2004-1355, 2005-1305, 2005-1323, 2005-1324, 2005-1325, 2005-1351, and 2006-1272), surficial geologic maps (Soller & Reheis 2004), geochemical databases (Earth Chem and others), and literature. State geologic maps composed of only bedrock geology were overlain with surficial map units of > 100 ft thicknesses to produce combined surficial bedrock geologic maps similar to other states. We translated these combined surficial bedrock geologic maps into characteristics by assigning an estimate of each map units chemical or physical properties to every occurrence of that map unit in the combined surficial bedrock geologic map. This estimate was calculated as the average of literature or database values of the respective chemical or physical property for each lithology contained within the map unit, weighted by the prevalence of each lithology within the map unit. We characterized geology based on the 201 different lithologies that the Geologic Map Database lists as occurring in the Conterminous U.S. Because some of these lithologies are known to vary widely in their chemical or physical attributes, we created an additional 76 lithologic classes based on common modifiers used in geologic unit descriptions to better parse physical or chemical variability within lithologies (e.g., calcareous and non-calcareous sandstone). Modifiers were assigned based on descriptions of geologic formations obtained through either the Lexicon of Geologic Names of the United States or literature searches. 14 lithologic classes were not characterized because either they were extremely rare and literature values of their properties were unavailable or the class was not a specific rock type (e.g., mlange, water, landslides). These classes remain uncharacterized as no data.