Sedimentary age models, benthic foraminifera, mass accumulation rates, and volcanic grain data from R/V Justo Sierra cruise in the Southern Gulf and Ixtoc I from 2015-08-03 to 2015-08-06

This dataset includes age models, benthic foraminifera species counts used for stable isotope analysis, mass accumulation rates and volcanic grain counts from 6 sediment cores collected throughout the southern Gulf of Mexico during the R/V Justo Sierra cruise in the Southern Gulf and Ixtoc I from 2015-08-03 to 2015-08-06. Samples were analyzed by gamma spectrometry with High-Purity Germanium (HPGe) gamma-ray detectors (Canberra Coaxial Planar configuration) for total 210Pb (46.5 keV), 214Pb (295 keV and 351 keV), and 214Bi (609 keV) activities. The mean activity of the 214Pb (295 keV), 214Pb (351 keV), and 214Bi (609 keV) was used as a proxy for 226Ra activity and therefore the supported 210Pb that is produced in situ. The reported excess 210Pb (210Pbxs) is the difference of the total 210Pb and the supported 210Pb. The constant rate of supply (CRS) model was used to establish a chronology (age model) and mass accumulation rates for each core. Age model uncertainty is expressed as 1 standard deviation. Mass accumulation rates are reported as grams per square centimeter per year (g/cm2/yr). The sand-size fraction (>63μm) was isolated by wet sieving. Potential volcanic glass-rich depth intervals were selected based on age models. 100 grains of the sand fraction counted under 100x magnification. Based on this method, there is a 95% chance of finding a grain type that makes up at least 3% of the sample. Sand-sized volcanic glass grains were visually identified based on smooth texture, glassy luster, conchoidal fracture pattern and dark color. Clear volcanic glass grains were not counted in this study, as the visual differences between clear volcanic glass and immature quartz grains are difficult to discern even at high magnification. Benthic foraminifera (C. wuellerstorfi and C. pachyderma) tests were picked from each sample to obtain greater than 50g of benthic foraminifera carbonate for stable isotope analysis. The numbers of each species used for each measurement are included (p= C. pachyderma, w= C. wuellerstorfi). All data are presented with depth (mm) below the core surface. The R/V Justo Sierra-Southern Gulf & Ixtoc I cruise on 2015-07-29 to 2016-08-11 objective was to characterize the distribution and fate of oiled sediment at sites on the continental shelf and slope of the Southern Gulf of Mexico with reference to the Ixtoc blowout (1979-1980) and the chief scientist was Dr. David Hollander. CTD and trace metals in sediment cores collected during the R/V Justo Sierra cruise and coastal sampling in the southern Gulf of Mexico are available under GRIIDC UDIs R4.x267.179:0019 and R4.x267.000:0115 respectively.