Grain Size
Data have been sorted into four categories, clay, fine silt, silt or coarse silt, and sand. In circumstances where only three categories were collected (clay, silt, and sand), the fine silt field was not populated. In all cases, it is assumed that the pipette method was used, unless specified. It is possible that some analyses designated as pipette were, in fact, hydrometer.
Clay Mineralogy
Clay mineralogy data were collected using semi-quantitative x-ray diffraction methods. Specifications on individual sample preparation and equipment setup are generally not available but are assumed to follow the procedures outlined in Hallberg, 1978 (IGS TIS-8).
Radiocarbon Dates
Radiocarbon dates may have been completed by a variety of laboratories and used numerous methods. For each date, the laboratory summary sheet is attached. Please refer to that sheet for information regarding sample type, preparation, dating method and accuracy.
pXRF
pXRF refers to portable x-ray fluorescence. Sample preparation varied. Please refer to individual studies for details on methodology.
Matrix Carbonate
Matrix carbonate data were generated using a chittick apparatus following the Iowa Geological Survey methods outlined in Hallberg, 1978 (IGS TIS-8).
Bulk Density
Specifications on individual sample preparation and equipment setup are generally not available, but are assumed to follow the procedures outlined in Klute, 1986.
Clast Lithology
Clast lithology data may have been collected using multiple methods, especially with respect to the grain-size analyzed and the specific lithology/mineralogy counted. If a particular lithology is not represented in the data, it may not indicate that it wasn’t present, but may indicate that it was not a focus of a particular study. IGS may be able to provide additional information regarding methodology in some cases.
Soil Carbon and Nitrogen
Elemental analysis by dry combustion and chromatography methods were used to determine total carbon percent, total nitrogen percent, and organic carbon percent unless otherwise specified. Soil organic matter percent was determined by loss on ignition.