Phillips, Stephen C. Pohlman, J.W. Casso, M. 2025 1 dataset DOI:10.5281/zenodo.15626975 Woods Hole Coastal and Marine Science Center, Woods Hole, Massachusetts, USA U.S Geological Survey, Coastal and Marine Hazards and Resources Program Suggested citation: Phillips, S.C., Pohlman, J.W., and Casso, M., 2025, Molecular (C1-C5 hydrocarbon, CO2, O2, and N2) and δ13C-CH4 composition of pressure core, void, and hydrate gases from the Terrebonne Basin, Gulf of America (Gulf of Mexico), Walker Ridge 313 Site H [Dataset]: Zenodo, https://doi.org/10.5281/zenodo.15626975 https://doi.org/10.5281/zenodo.15626975 These data include composition of void gas, pressure core gas, and hydrate gas samples collected from the Terrebonne Basin in the Gulf of America (Gulf of Mexico) at Walker Ridge Site H, Holes H003 and H002. Cores were collected during drilling as part of the Deepwater Hydrate Coring Expedition (UT-GOM2-2) in August 2023. This U.S. Department of Energy funded project was focused on better understanding microbial methane generation in marine sediments and characterizing coarse-grained gas hydrate reservoirs. Sediments were recovered continuously down to 155 meters below the seafloor and as spot cored intervals down to 861 meters below the seafloor. Cores were recovered using both conventional and pressure cores. Gas samples were collected from both conventional and pressure cores in order to understand the source of gases in Terrebonne Basin sediments. Gas samples were analyzed for C1-C5 hydrocarbon, CO2, O2, N2, and δ13C-CH4 composition using gas chromatography and cavity ringdown spectroscopy. The molecular and isotopic composition of hydrocarbon gases can be used to constrain the source of gas in hydrate-bearing sediments. Measurement of oxygen and nitrogen is to track atmospheric contamination. This Microsoft Excel workbook contains data in a single tab. The samples were collected from cores recovered during the UT-GOM2-2 expedition in 2023. All samples were collected either during offshore operations in August 2023 or onshore operations in September 2023. Additional information with regards to the offshore operations (field activity 2023-021-FA) can be found at https://cmgds.marine.usgs.gov/services/activity.php?fan=2023-021-FA 20230804 20230827 Ground condition. Cores were collected in August 2023 on the D/V Q4000 using conventional (advanced piston coring and extended core barrel coring) and pressure coring (Pressure Coring Tool with Ball Valve). Void gases were collected from conventional cores immediately after recovery by drilling a hole through the core liner. Pressure cores were collected from a bubbling chamber (an inverted graduated cylinder) during pressure core degassing. Hydrate gases were collected from cryo-frozen hydrate-bearing sediment samples that were dissociated inside a syringe used to collect the gas. Complete Future version expected with analysis of additional gas samples. -91.67608 -91.67599 26.66260 26.66228 None U.S. Geological Survey USGS Coastal and Marine Hazards and Resources Program CMHRP Woods Hole Coastal and Marine Science Center WHCMSC U.S. Department of Energy DOE National Energy Technology Laboratory NETL University of Texas at Austin UT-Austin methane hydrates carbon cycle gas analysis USGS Thesaurus drilling and coring piston coring rotary drilling core analysis chemical analysis diagenesis gas chromatography light stable isotope analysis interagency programs ISO 19115 Topic Category geoscientificInformation USGS Metadata Identifier USGS:26031589-92db-464b-9ee1-1ae82c713d3e Geographic Names Information System (GNIS) Gulf of America None Terrebonne Basin Gulf of Mexico Walker Ridge Protraction Area No access constraints. Please see 'Distribution Information' for details. Public domain (CC0-1.0) data from the U.S. Government are freely redistributable with proper metadata and source attribution. Please recognize the U.S. Geological Survey (USGS) as the source of this information. All data collection was funded by the U.S. Department of Energy National Energy Technology Laboratory. Stephen Phillips U.S. Geological Survey, Northeast Region, Woods Hole Coastal and Marine Science Center Research Geologist mailing and physical address

384 Woods Hole Rd.

Woods Hole MA 02543-1598 508-457-8700 x2240 scphillips@usgs.gov For each of the gas measurements described in the Process Steps below, standards relevant to the particular property were entrained in the measurement sequence to ensure fidelity within each Process Step. The standards are noted in the Process Steps as well as the citations for those references. This Microsoft Excel workbook represents the complete collected and calculated data in support of dual-frequency magnetic susceptibility measurements for the UT-GOM2-2 project. Horizontal position was determined by GPS satellite data, which provided guidance information for the dynamic positioning system (DPS) utilized by the D/V Q4000. The DPS also utilizes inputs from current, wind, tide, and wave data to control eight azimuthal thrusters beneath the ship’s hull. The thrusters are capable of 360-degree adjustment. Given the DPS capabilities, borehole locations for the D/V Q4000 are considered to be accurate to a radius of 15 meters. Details for a very similar DPS system us provided in: Chikyu Hakken – Earth Discovery, Volume 1, Spring 2005, published by JAMSTEC’s Center for Deep Earth Exploration: https://www.jamstec.go.jp/chikyu/e/magazine/backnum/pdf/hk_01_e.pdf North American Datum 27 (NAD27) is the horizontal datum used by the DPS on the D/V Q4000. Coring depth measurements used on the D/V Q4000 during the UT-GOM2-2 expedition followed standard International Ocean Discovery Program (IODP) protocols using analogous coring tools. Assessment of these protocols by IODP had determined the vertical position accuracy is on the order of centimeters to meters relative to each coring point, depending on core recovery. Additional information about the depth conventions and accuracy are on pages 8 and 9 of the IODP report “IODP Depth Scales Terminology”: http://www.iodp.org/policies-and-guidelines/142-iodp-depth-scales-terminology-april-2011/file. Depth resolution ranges from 0.01 to 1 meter. Sediment cores were collected via wireline coring tools (advance piston coring, extended core barrel coring, and pressure coring) and cut into sections at sea. Hole H002 is located at 26.66228° latitude and -91.67601° longitude at the seafloor. Hole H003 is located at 26.66263° latitude and -91.67599° latitude at the seafloor. Void gases were collected using a syringe and a puncture tool that penetrates the core liner. Pressure core gases were collected from an inverted graduated cylinder as part of the quantitative degassing system that collects gases produced from the core storage chamber during depressurization. Hydrate gases were collected from cryogenically frozen samples that were allowed to dissociate within a syringe. Void gas, pressure core gas, and hydrate gas were collected in Cali-5 Bond gas bags and were analyzed for gas composition and methane stable carbon isotopes at the U.S. Geological Survey Woods Hole Coastal and Marine Science Center using the Automated Sample Introduction Module (Auto-SIM) Gas Chromatography/Cavity Ring-Down Spectroscopy System (Auto-SIM GC/CRDS). Gas samples in Cali-5 Bond bags were attached to the 16-port Auto-SIM that automatically transfers a portion of each sample to a series of samples loops of the Auto-SIM GC/CRDS that includes the USGS Discrete Sample Introduction Module (DSIM) with a cavity ring-down spectrometer and a Scientific Research Instruments (SRI) MultipleGas#5 (MG5) gas chromatograph (GC) equipped with sample loops and injection valves for parallel analysis by flame ionization detection (FID) and thermal conductivity detection (TCD). The DSIM contains a fixed (low-volume) internal sample loop and a replaceable external sample loop (larger-volume) that allows the user to properly dilute gases so they’re within the ideal analytical range of a Picarro G2201-I CRDS (100-600 ppm). The CRDS measures methane and CO2 concentrations and stable carbon isotopes of each (see Pohlman and others (2021) for additional details). Isotope ratios measured by the CRDS are reported in the -notation (δ13C) relative to a Vienna Pee Dee Belemnite (VPDB) standard calibration. Measurement precision for methane isotope ratios improves from 1‰ at 10 ppm to less than 0.2‰ at 30 ppm and remains constant through the range of measurements made. The average sample precision for this project was 0.18‰ for methane carbon isotope ratios. Additional details of the gas collection and analysis procedures are described in Flemings and others, 2025. Reference: Flemings, P.B., Thomas, C., Phillips, S.C., Collett, T.S., Cook, A.E., Solomon, E., Colwell, F.S., Johnson, J.E., Awwiller, D., Aylward, I., Bhandari, A.R., Brooks, D., Buser-Young, J.Z., Cardona, A., Casso, M., Coyte, R., Darrah, T., Davis, M., Dugan, B., Duncan, D., Germaine, J.T., Holland, M., Houghton, J., Mills, N.T., Mimitz, M., Minarich, D., Morono, Y., Murphy, Z., O’Connell, J., Petrou, E., Pettigrew, T., Pohlman, J.W., Portnov, A., Phillips, M.P., Redd, T., Sawyer, D. E., Schultheiss, P., Shannon, K., Sullivan, C., Small, C., Tozier, K., Tsang, M.-Y., Maal, C.V.D., Waite, W.F., and Walton, T., 2025, Expedition UT-GOM2-2 Methods, in Flemings, P.B., ed., Proceedings of the Deepwater Hydrate Coring Expedition UT-GOM2-2: The University of Texas at Austin, University of Texas Institute for Geophysics, https://doi.org/10.5281/zenodo.13971228. Pohlman, J.W., Casso, M., Magen, C., and Bergeron, E., 2021, Discrete Sample Introduction Module for Quantitative and Isotopic Analysis of Methane and Other Gases by Cavity Ring-Down Spectroscopy: Environmental Science and Technology, v. 55, p. 12066-12074, https://doi.org/10.1021/acs.est.1c01386 2024 Stephen Phillips U.S. Geological Survey, Northeast Region, Woods Hole Coastal and Marine Science Center Research Geologist mailing and physical address

384 Woods Hole Rd.

Woods Hole MA 02543-1598 508-457-8700 x2240 scphillips@usgs.gov Point Point 79 0.00001 0.00001 decimal degrees NAD 27 Clark ellipsoid of 1866 6378206.400000 294.9786982 local surface - depth below sea floor 0.005 meters attribute values "UT-GOM2-2_USGS-gas-data.xlsx" Microsoft Excel workbook that contains tabulated gas composition data by depth for UT-GOM2-2 cores. producer defined Expedition Expedition name. UT-GOM2-2 for all entries U.S. Geological Survey user defined text field Area Lease block area within the Gulf of America. All values are Walker Ridge 313 (WR313). U.S. Geological Survey user defined text field Site Site within the WR313 area. In this case all from the H site. U.S. Geological Survey user defined text field Hole Two holes were drilled at the WR313 H site: Holes 002 and 003. U.S. Geological Survey user defined text field Core Core number, increasing with depth in each hole. U.S. Geological Survey user defined Core type Core type used to recover core. H is advanced piston core, X is extended core barrel, CS is pressure coring tool with ball valve in the cutting shoe configuration, and FB is the pressure coring tool with ball valve in the face bit configuration. U.S. Geological Survey user defined Section Section cut within the core. Increasing number within the core with the core catcher (CC) as the bottom section U.S. Geological Survey user defined Piece Piece cut within each core section. Some sections were not cut into pieces. NaN = no data. U.S. Geological Survey user defined Sample type Void gas was collected from voids within the core liner in conventional cores. Pressure core gas was collected from gas produced during depressurization of pressure cores. Hydrate gas was collected from cryo-frozen cores in which hydrate-bearing sediment was allowed to dissociate within a syringe. U.S. Geological Survey user defined Gas bag # Number label on each Cali-5 bond gas bag. U.S. Geological Survey 800 880 no unit Pressure core step (bar) Pressure within the pressure core storage chamber when the gas sample was collected. U.S. Geological Survey 0 30 bar Compressed sample top depth (mbsf) Sample top depth in meters below seafloor (mbsf) based on linearly-compressed core depths, accounting for expansion of the core (total length of core = length of drilling advance). Equivalent to IODP CSF-B terminology. U.S. Geological Survey 19.64 818.69 meters below seafloor (mbsf) Compressed sample bottom depth (mbsf) Sample bottom depth in meters below seafloor (mbsf) based on linearly-compressed core depths, accounting for expansion of the core (total length of core = length of drilling advance). Equivalent to IODP CSF-B terminology. U.S. Geological Survey 19.64 818.87 meters below seafloor (mbsf) Methane (%) Concentration of methane (C1) within the gas sample. U.S. Geological Survey 2.04 100.00 percent (%) δ13C-CH4 (‰) δ13C of methane relative to Vienna Pee Dee Belemnite (VPDB). U.S. Geological Survey -83.5 -69.9 per mil (‰) CO2 (ppm) Concentration of carbon dioxide in the sample. U.S. Geological Survey 197 11052 parts per million (ppm) Ethane (ppm) Concentration of ethane (C2) in the gas sample. U.S. Geological Survey 1.8 114.8 parts per million (ppm) Propane (ppm) Concentration of propane (C3) in the gas sample. U.S. Geological Survey 1 8 parts per million (ppm) C1/(C2+C3) Ratio of methane (C1) to ethane (C2) plus propane (C3). U.S. Geological Survey 8076 63201 no unit C1/C2 Ratio of methane (C1) to ethane (C2). U.S. Geological Survey 8076 80025 no unit i-Butane (ppm) Concentration of isobutane (i-C4) in the gas sample. U.S. Geological Survey 1 6 parts per million (ppm) n-Butane (ppm) Concentration of normal butane (n-C4) in the gas sample. U.S. Geological Survey 1 3 parts per million (ppm) neo-Pentane (ppm) Concentration of neopentane (neo-C5) in the gas sample. U.S. Geological Survey 2 2 parts per million (ppm) i-Pentane (ppm) Concentration of isopentane (i-C5) in the gas sample. U.S. Geological Survey b.d. b.d parts per million (ppm) n-Pentane (ppm) Concentration of normal pentane (n-C5) in the gas sample. U.S. Geological Survey b.d. b.d. parts per million (ppm) Oxygen (%) Concentration of oxygen within the gas sample. U.S. Geological Survey 0.77 20.23 percent (%) Nitrogen (%) Concentration of nitrogen within the gas sample. U.S. Geological Survey b.d. 80.40 percent (%) The workbook UT-GOM2-2_USGS-gas-data.xlsx contains one tab. The first row in the XLSX file is a header row. The remaining rows contain all data included in this data release, with non-measurements given by “NaN" as indicated in the attribute definitions in this xml file. Measurements that had concentrations below detection are listed as “b.d.” This file is part of a data release posted to the Zenodo UT-GOM2-2 community. Phillips, S.C., Pohlman, J.W., and Casso, M (2025). Molecular (C1-C5 hydrocarbon, CO2, O2, and N2) and δ13C-CH4 composition of pressure core, void, and hydrate gases from the Terrebonne Basin, Gulf of America (Gulf of Mexico), Walker Ridge 313 Site H [Dataset]. Zenodo. https://doi.org/10.5281/zenodo.15626975. Zenodo mailing and physical address

European Organization for Nuclear Research: IT Department, Digital Repositories Section

Meyrin Geneva 1211 Switzerland +41 22 76 77777 info@zenodo.org Zenodo makes research results citable, and through OpenAIRE, integrates them into existing reporting lines to funding agencies. Citation information is also passed to DataCite and onto the scholarly aggregators. UT-GOM2-2_USGS-gas-data.xlsx (Excel spreadsheet of data). The Zenodo site does not have the complete XML metadata. Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data for other purposes, nor on all computer systems, nor shall the act of distribution constitute any such warranty. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. XLSX Created in Excel Office 365 version 2408 1 https://doi.org/10.5281/zenodo.15626975 The link is the DOI link to the data release landing page where the data can be downloaded. None. 20251208 Stephen C. Phillips U.S. Geological Survey, Northeast Region, Woods Hole Coastal and Marine Science Center Research Geologist mailing and physical

U.S. Geological Survey

384 Woods Hole Rd.

Woods Hole MA 02543-1598 508-548-8700 x2240 whsc_data_contact@usgs.gov The metadata contact email address is a generic address in the event the person is no longer with USGS. Content Standard for Digital Geospatial Metadata FGDC-STD-001-1998 None None