Sediment grain size data from samples collected offshore Oceanside, southern California during field activity 2017-686-FA from 2017-10-23 to 2017-10-31

Twenty-six sediment samples were collected on October 31, 2017 at a total 23 locations using a small Van Veen grab sampler from the R/B Park Snavely in water depths between 20 and 80 meters.

The grain-size distributions of sediment samples were determined in the USGS Pacific Coastal and Marine Science Center (PCMSC) sediment lab. Approximately 20g of sediment was sub-sampled and 10mL of 35 percent hydrogen peroxide was added to sit overnight to remove organics. The sample was heated at 250 degree C to remove any remaining hydrogen peroxide and was placed in an ultrasonic bath to liberate the mud (silt and clay) fraction. Subsequently the sample was centrifuged for 1/2 hour and 1 hour to remove soluble salts. Samples were funneled through a 2mm and a 63um sieve to separate the gravel (>2mm), sand (63um to 2mm), and mud (<63um). Both sand and gravel fractions were dried in an 80 degree C oven and weighed. 5mL of 10 percent sodium hexametaphosphate was added to the mud fraction cylinder and distilled water was added to total the volume to 1L. The mud and calgon solution sat overnight to ensure removal of the negative charges from the mud particles. Subsequently, a 20mL aliquot was taken from the 1L mud fraction to determine the weight of the mud. The particle size distribution of the mud and sand fractions were analyzed separately via the Beckman Coulter LS 13 320 aqueous liquid module. The gravel fraction particle size was analyzed via dry sieving. The gravel, sand, and mud grain size data were all reincorporated back together using the pcSDSZ program in the PCMSC sediment lab, and the grain size data was reported in percent 1/4-phi size intervals.