Dataset: Sediment multicore general organic, inorganic, stable isotope, and bulk radiocarbon data collected from R/V F.G. Walton Smith cruise WS23-139 along the Guianas mudbanks coast in June and July 2023

Multicores from 14 different stations along the Guianas mudbanks coast (NE S. America, Brazil, French Guiana, and Suriname) were extruded and frozen aboard the R/V F.G. Walton Smith in the summer of 2023. Samples were subsequently portioned, with some portions dried (freeze-drying and oven-drying), acid-treated, and/or ground. Samples were analyzed in duplicate (acid-treated and not acid-treated) on an elemental analyzer connected to an isotope ratio mass spectrometer (IRMS) for nitrogen quantity and stable nitrogen isotope values (not acid-treated) and for carbon quantity, stable carbon isotope values, and carbon:nitrogen ratios (acid-treated). 

A subset (n=35) of acid-treated samples was analyzed for bulk radiocarbon content. A subset (n=25) of non-acid-treated, unground samples was run for surface area, and all non-acid-treated and unground samples were measured for inorganic elemental content and grain size distribution. Sample names in this dataset include the code for the seagoing expedition (WS23-139), the multicore number, and the extrusion depth (in centimeters) from the multicore. Columns are provided with station numbers, latitude, longitude, and station name. The 14 stations aligned in sets of 3 cross-shelf transects (inner, middle, and outer) at 6 different locations along this coast. 

Sediment samples were extruded on board the ship after cores were recovered. Extruded intervals were measured using a rotating core table on a calibrated threaded rod (Schwing et al., 2016). Extruded samples were placed in pre-combusted glass jars with pre-combusted foil covers and threaded lids, and they were frozen on board the ship. Upon return to the laboratories at the University of South Florida, samples were thawed and separated into three aliquots: acid treatment, no acid treatment, and archive.

Archive aliquots were refrozen.

Acid treatment consisted of rinsing with 1N HCl in pre-combusted glass beakers and rinsing with distilled water until pH testing strips rose to a stable pH when contacted with siphoned rinse water from the sediments. The sediments were dried at 50 degrees Celsius and ground. This aliquot was used for carbon isotopes, %TOC, C:N ratios, and radiocarbon measurements.

The non-acid-treated samples were divided for grain size analysis, surface area analysis, and inorganic geochemistry (undried, unground) and for nitrogen isotope, %C, and %N analyses (dried and ground). The %CaCO3 of the samples was calculated using the difference between %C and %TOC measurements, the latter of which had carbonate minerals removed by acid treatment, and the %TOC values were corrected for the missing mass of CaCO3 by multiplying the measured values by the term (1-%CaCO3). Both corrected and measured %TOC values are provided.