VISUAL BASIC SOFTWARE FOR PROCESSING SEDIMENT GRAIN-SIZE DATA

Methods and nomenclature that describe and summarize sediment grain-size distributions are important to geologists because of the large amount of information contained in textural data sets. To facilitate reduction of sedimentologic data within modern computing environments, we have written two programs: GSSTAT - to generate grain-size statistics and extrapolate particle distributions, and SEDCLASS - to classify sediment grain-size distributions based on the relationship between size fractions. Our programs are written in Microsoft Visual Basic 6.0, run on Windows 95/98/ME/NT/2000/XP computers, provide a window to facilitate execution, allow users to select options with mouse-click events or through interactive dialogue boxes, supply detailed internal documentation, and generate error messages warning the user of potential problems.

The program GSSTAT permits users to select output as either inclusive graphics or moment statistics, to extrapolate distributions to the colloidal-clay boundary by three methods, to convert between frequency and cumulative frequency percentages, to calculates percentages of gravel, sand, silt and clay, and to generate verbal descriptions of the statistics. The program SEDCLASS permits users to select output in either the Shepard (1954) classification scheme as modified by Schlee (1973), or the Folk (1974) scheme, the two most common classification schemes used by sedimentologists. Input and output files for both programs consist of comma-delimited ASCII text. Compiled and uncompiled versions of the software with the necessary support files, installation instructions, and documentation are available free of charge from the USGS.