Location and analyses of sediment samples collected on Stellwagen Bank off Boston, Massachusetts from November 5, 2013 to April 30, 2019 during U.S. Geological Survey field activities

These attribute definitions describe each column of information in the Excel spreadsheet with the exception of additional information in the last column of the Excel spreadsheet. That column contains an explanation of the ANAL_COMM values and how the quality grade is assigned. That column of information is omitted from the CSV and shapefile. The shapefile truncates attribute lablels to 10 characters, so the finall attribute is presented as AQ_QC_COMM in the shapefile. The first row of the spreadsheet is the column heading. The CSV file has the same information and the column definitions are the same - with the last column of the XLSX file omitted (data quality grade explanation). The information in the last column of the XLSX is as follows:
Data quality grades may be determined by several factors, and any comments or notes that indicate the data for a particular sample may be suspect are included in the results table for that sample under "comments". Quality grades for sample data that do not have any additional comments are assigned based on the calculated percent difference between the weights of the coarse fraction remaining after wet sieving and the sum of all of the weighed fractions after dry sieving the coarse fraction, indicating an estimated differing amount of material which could skew the calculated grain size results.
A = percent differences between 0% and ±1.5%
B = percent differences between ±1.5% and ±3%
C = percent differences between ±3% and ±4.5%
D = percent differences greater than ±4.5%
Negative weight percents in phi size distributions and gravel-sand-silt percentages may be the result of a lack of fines present in the actual samples. The statistical spreadsheet used to calculate grain size distribution takes measured weights for the coarse fractions (after wet sieving through a 4 phi sieve) and merges it with the cumulative frequency data obtained from the Multisizer for any fine fraction that remains after wet sieving. These equations include determining the percentage of the sample in fine fraction phi weight percents (5 phi to 11 phi). This fine fraction weight is determined by subtracting the wet sieved portion of the sample from the calculated total weight of the sample (determined after calculating and removing the weight of the water in the sample and weight of salt). If there is any excess mass, no matter how small, determined to be in the coarse fraction weights and not in the corrected weight if the entire sample, the calculations subtract this excess weight from the fines phi distribution to make the sum of the weight percents equal 100%.