Scientists from the U.S. Geological Survey (USGS), St. Petersburg Coastal and Marine Science Center (SPCMSC), in collaboration with the U.S. Army Corps of Engineers (USACE), conducted geophysical and sedimentological surveys around Cat Island, the westernmost island in the Mississippi-Alabama barrier island chain. The objectives of the study were to understand the geologic evolution of Cat Island relative to other barrier islands in the northern Gulf of Mexico and to identify relationships between the geologic history, present day morphology, and sediment distribution. This report serves as an archive of 11 terrestrial and 29 marine sediment vibracores collected August 4-6 and October 20-22, 2010. Geographic Information System (GIS) data products include marine and terrestrial core locations and 2007 shoreline. Additional files included: marine and terrestrial core description logs, core photos, grain-size analysis, optically stimulated luminescence (OSL) dating and Carbon-14 dating locations and results, Field Activity Collection System (FACS) logs, and formal Federal Geographic Data Committee (FDGC) metadata (please refer to the data products and downloads page at
http://pubs.usgs.gov/ds/xxx/Data_Products_and_Downloads_Cat_cores.html).
The 10BIM06_Grainsize_Summary_Statistics.xlsx file includes all sediment grain-size analysis results from marine vibracores collected around Cat Island, Mississippi in October 2010 by the U.S. Geological Survey (USGS), St. Petersburg Coastal and Marine Science Center. Multiple data types were collected throughout the duration of this project; however, only the results of the sediment component are presented in this archive data series.
Samples for grain-size analysis were collected from the top, middle, and bottom of each lithologic unit in approximately 2-3 cm intervals. Grain-size analyses on the core sediment samples were performed using a Coulter LS 200 (
https://www.beckmancoulter.com/) particle-size analyzer, which uses laser diffraction to measure the size distribution of sediments ranging in size from 0.4 microns (µm) to 2 millimeter (mm) (clay to very coarse-grained sand). A total of 367 core samples were analyzed. In order to prevent shell fragments from damaging the LS 200, particles greater than 1 mm in diameter were separated from all samples prior to analysis using a number 18 (1000 µm) U.S. standard sieve, which meets the American Society for Testing and Materials (ASTM) E11 standard specifications for determining particle size using woven-wire test sieves. Two subsamples from each sample were processed through the LS 200 a minimum of three runs each. The LS 200 measures the particle-size distribution of each sample by passing sediment suspended in solution between two narrow panes of glass in front of a laser. Light is scattered by the particles into characteristic refraction patterns measured by an array of photodetectors as intensity per unit area and recorded as relative volume for 92 size-related channels (bins). The size-classification boundaries for each bin were specified based on the ASTM E11 standard. The raw grain-size data were then run through the free, widely available program GRADISTAT (Blott and Pye, 2001;
http://www.kpal.co.uk/gradistat.html), which calculates the geometric (in metric units) and logarithmic (in phi units, F; Krumbein, 1934) mean, mode, sorting, and skewness of each sample using the Folk and Ward (1957) method. GRADISTAT also calculates the fraction of sediment from each sample by size category (for example, clay, coarse silt, fine sand, etc.) based on a modified Wentworth (1922) size scale. A macro developed by the USGS was applied to calculate the average and standard deviation of each sample set (6 runs per sample), and highlight runs that varied from the set average by more than ±1.5 standard deviations. Those runs were removed from the results and the sample average was recalculated using the other five runs. The individual core and sample GRADISTAT files associated with this project(10BIM06_GrainSize_Gradistat.zip)are available for download at
https://doi.org/10.3133/ds834/data/tables/10BIM06_GrainSize_Gradistat.zip. Results from this output table were summarized in file 10BIM06_GrainSize_Summary_Statistics.xlsx which is available for download at
https://doi.org/10.3133/ds834/data/tables/10BIM06_GrainSize_Summary_Statistics.zip. This metadata is pertinent to the summary statistics file.
