Grain-size analysis results and locations of sediment samples collected in Little Egg Inlet and offshore the southern end of Long Beach Island, NJ, during USGS Field Activity 2018-049-FA (simplified point shapefile and CSV files)

Seventy stations were occupied aboard the R/V Rafael during USGS survey 2018-049-FA with the mini-SEABOSS (Blackwood and Parolski, 2001). The mini-SEABOSS was equipped with a Van Veen grab sampler, two GoPro HERO4 Black digital cameras, and a downward-looking video camera. Physical sediment samples were collected at 68 of the 70 sampling sites. Sediment samples were only attempted in areas where collecting a sample would not damage the mini-SEABOSS; therefore, no samples were collected in areas with a cobble, boulder, or rocky seabed, as identified in real time using the top-side live video feed. At two sites (2018-049-FA-026 and 2018-049-FA-047), a sample was attempted but was not successfully collected. The sediment sample collection times were recorded in the survey log when the sampler was lifted from the seabed (the Van Veen sampler closed and collected a sample as it was lifted off the sea floor). These manually recorded times would later be used to derive the sample location. Once the sampler was recovered on deck, a subsample was taken for grain-size analysis at the sediment laboratory at the USGS Woods Hole Coastal and Marine Science Center. This process step and all subsequent steps were performed by the same person unless otherwise noted.

Differential GPS (DGPS) navigation from the ship's receiver was logged through HYPACK navigation software and in ArcGIS using the ArcMap GPS extension. The DGPS was set to receive fixes at a one-second interval in geographic coordinates (WGS 84). Dates and times were recorded in Coordinated Universal Time (UTC). Sediment sample locations were determined by matching the sampling time recorded in the survey log with the time in the navigation logs using the Python Notebook Grabs_LatLong_NJ2018_HYPACK.ipynb. Approximate depth was derived by extracting the depth values from the preliminary bathymetry data collected during USGS field activity 2018-001-FA (2018001FA_Sept2018_4m.tiff) in QGIS (version 3.4) the Point Sampling Tool plugin.

Samples submitted to the sediment analysis laboratory for grain size analysis using the Horiba laser diffraction unit (LA-960) and sieving of the ≥ -2 phi fraction are assigned unique analysis identifiers (ANALYSIS_ID) and divided into batches of no more than 30 samples. Each batch is entered into a Microsoft Excel data entry spreadsheet (LD Worksheet Template_xxxx.xlsx, where xxxx is the identifier assigned to the sample submission) to record the initial and dried sample weights, as well as the sieved coarse fraction weights. Each batch is also entered into macro-enabled Microsoft Excel data entry spreadsheets (GrainSizeWorksheet_LD1-30_xxxx(batch_yy).xlsm or GrainSizeWorksheet_LD31-600_xxxx(batch_yy).xlsm, where xxxx is the identifier assigned to the sample submission, 'LD1-30' and 'LD31-60' refer to the pre-labeled and weighed glass laser diffraction vials the samples will be run in, and 'batch_yy' refers to the sample batch) to record the measurement data coming from the laser diffraction unit and incorporate the initial, dried, and sieved weights.
About 10-15 grams of wet sediment are placed in a pre-weighed beaker and the gross weight is recorded. The sample is wet sieved through a 4 mm (No. 5) sieve. If there is any coarse fraction remaining in the sieve, the coarse material is oven dried at 100°C in a pre-weighed beaker and weighed again when dry. This coarse fraction is dry sieved to determine the individual weights of the -2 to -5 phi fractions, and the weights are recorded in the data entry spreadsheet LD Worksheet Template_xxxx.xlsx. The fine fraction in water is collected in a pre-labeled and weighed glass laser diffraction vial. If there is any coarse fraction remaining in the sieve from wet sieving, this vial is also oven dried at 100°C and weighed when dry. If there is no coarse fraction remaining from wet sieving, the sample can proceed directly to processing for analyses by the Horiba laser diffraction unit (LA-960).
Fine fractions ready for analysis by the Horiba laser diffraction unit are rehydrated with distilled water if they've been dry. Fifteen (15) ml of pre-mixed 40 g/l sodium hexametaphosphate [(NaPO3)6] are added to each sample. If the height of the fluid in the laser diffraction vial is less than 5 cm, more distilled water is added to raise the level to no more than 8 cm in the vial. The samples are gently stirred, covered, and allowed to soak for at least 1 hour (for samples that were not dried) up to 24 hours (for samples that were dried). Soaked vials are placed into an ultrasonic bath and run for 10 minutes at a frequency of 37 Hz with a power level of 100. If the samples appear to be fully disaggregated, they are placed into pre-determined autosampler locations, and are run using the Horiba LA-960 for Windows software to get the fine fraction grain size distributions. The fine fraction distribution data are added to the appropriate data entry spreadsheets (GrainSizeWorksheet_LD1-30_xxxx(batch_yy).xlsm or GrainSizeWorksheet_LD31-600_xxxx(batch_yy).xlsm). The spreadsheet is used to calculate a continuous phi class distribution from the original fractions.

Continuous phi class distribution from the original fractions are transposed to the "results" tab in the macro-enabled Microsoft Excel data entry workbook (GrainSizeWorksheet_LD1-30_xxxx(batch_yy).xlsm or GrainSizeWorksheet_LD31-600_xxxx(batch_yy).xlsm, where xxxx is the identifier assigned to the sample submission, 'LD1-30' and 'LD31-60' refer to the pre-labeled and weighed glass laser diffraction vials the samples will be run in, and 'batch_yy' refer to the sample batch). Macros in the workbook ('GS_MoM_Arithmatic,' 'GS_statistics,' and 'sedimentname') are run to calculate grain size classification and statistical analyses and finish processing the data. Sample, navigation, and field identifiers, along with continuous phi class distribution data, grain size classification, and statistical analysis results are copied and pasted into a final Microsoft Excel spreadsheet (xxxx_GS-LD_results.xlsx, where xxxx is the batch number assigned to the sample submission). The processed data are quality control checked and assigned a quality grade based on the examination of the analytical data. Processed data are released to the submitter and incorporated into the laboratory's database. All raw analytical data generated by the samples are archived in the sediment analysis laboratory.

The Microsoft Excel spreadsheet was then saved as a CSV file (2018-049-FA_samples_GS-LD.csv) and opened in QGIS (version 3.8). A simplified shapefile of the sediment analyses was created by removing the attribute fields for STDEV, SKEWNESS, KURTOSIS, MEDIAN and other Method of Moments Statistics [e.g. D10], and the individual phi measurements [e.g., PHI_11] prior to export.