This dataset contains gas composition data from headspace gas samples (sample code HS). Sediment plugs were collected from an exposed core cut adjacent to the standard whole round sampling set onboard the Q4000. The plugs were sealed in glass vials after being fixed with potassium chloride. Gas was extracted from the vials at The Ohio State University and analyzed for gas composition using a Thermo Fisher Trace 1310 Gas Chromatograph (GC) equipped with a thermal conductivity detector (TCD) and flame ionization detector (FID), and a Standard Research Systems (SRS) quadrupole mass spectrometer. See Expedition UT-GOM2-2 Methods: Gas Geochemistry (Flemings et al., 2025a, https://doi.org/10.5281/zenodo.13971228). The attached readme file, previewed below, describes the data file in this dataset and its contents. The readme file also contains links to where the data is presented in the expedition proceedings. Additional data you might expect to find in this dataset can instead be found at the following locations: The sample depths can be found in the Curation dataset (http://doi.org/10.5281/zenodo.14926309). Download the file UT-GOM2-2 CORE LOG depths – sortable.xlsx, see tab “Sample-measurement log” sample code “HS”. Gas composition of voids, pressure cores, and dissociated gas hydrate can be found in the USGS Gas Geochemistry dataset (https://doi.org/10.5281/zenodo.15626975). Gas composition of additional void samples using an Inficon Fusion MicroGC chromatograph can be found in the void gas geochemistry dataset (https://doi.org/10.5281/zenodo.16689630).