Isabelle M. Shapiro Katlin Bowman Adamczyk Amy Gartman 20260612 comma-delimited text data release DOI:10.5066/P14JMPDV Pacific Coastal and Marine Science Center, Santa Cruz, California U.S. Geological Survey https://doi.org/10.5066/P14JMPDV https://cmgds.marine.usgs.gov/data-releases/datarelease/10.5066-P14JMPDV/ This data release contains porewater oxygen microprofiling data from abyssal sediment cores collected from the Samoa Basin in the South Pacific Ocean within the American Samoa Exclusive Economic Zone. Sediment cores were collected from 35 locations using a box core that was subsampled with push cores. Push cores were immediately transferred to a cold laboratory van, and oxygen was measured using Unisense microsensors inserted through pre-drilled holes in the core liner, spaced at 1 centimeter intervals. These measurements were completed within 3 hours of boxcore recovery. These data were collected shipboard in 2026 on expedition 2026-604-FA. These data serve to expand the knowledge and statistics for deep ocean marine mineral occurrences and composition within the global ocean. The expedition 2026-604-FA was the third leg of the National Oceanic and Atmospheric Administration’s American Samoa Abyssal Mapping effort, OPR-T900-KR-26. The USGS effort was supported in part by Interagency Agreement M20PG00028 between the USGS and the Bureau of Ocean and Energy Management. Additional information about the field activity or activities from which these data were derived is available online at: https://cmgds.marine.usgs.gov/fan_info.php?fan=2026-604-FA Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. 20260412 20260512 Date that the last process step was completed Complete None planned -167.8617 -165.6202 -13.1707 -17.0354 USGS Metadata Identifier USGS:6716e4b8-b784-4166-a1db-38e69fef6cec ISO 19115 Topic Category oceans geoscientificInformation Data Categories for Marine Planning Nonliving Resources Material Resources Mineral Resources Physical/Chemical Features Assessments USGS Thesaurus chemical analysis sea-floor characteristics marine geology core analysis Marine Realms Information Bank (MRIB) keywords seabed sediment mineral resources chemical analysis field observation box coring push coring marine geology None U.S. Geological Survey USGS Coastal and Marine Hazards and Resources Program CMHRP Pacific Coastal and Marine Science Center PCMSC Global Ocean Mineral Resources Geographic Names Information System (GNIS) South Pacific Ocean Territory of American Samoa NGA GEOnet Names Server (GNS) Samoa Basin No access constraints USGS-authored or produced data and information are in the public domain from the U.S. Government and are freely redistributable with proper metadata and source attribution. These data are marked with a Creative Commons CC0 1.0 Universal License. Please recognize and acknowledge the U.S. Geological Survey as the originator of the dataset and in products derived from these data. U.S. Geological Survey, Pacific Coastal and Marine Science Center PCMSC Science Data Coordinator mailing and physical

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Santa Cruz CA 95060 831-427-4747 pcmsc_data@usgs.gov Mac OSX 11.6.1, Microsoft Excel 16.47.1 for Mac Unisense A/S 2020 Unisense A/S, 2020, Oxygen microsensor: Unisense Scientific web page, accessed 2026, at https://unisense.com/products/o2-microsensor/. https://unisense.com/products/o2-microsensor/ Unisense A/S 2025 Unisense A/S, 2025, uSense Log: Unisense Scientific Software, accessed 2026, at https://unisense.com/product-category/software/. https://unisense.com/product-category/software/ Oxygen electrodes were calibrated approximately once every 24 hours with a two point-calibration using zero-oxygen solution (Unisense Zero-oxygen calibration kit, Lot: 1.28 and 1.27; https://unisense.com/products/oxygen-calibration-kit/) and oxygen saturated solution. The oxygen saturated solution was created in a Unisense CAL300 calibration chamber (https://unisense.com/products/calibration-chamber/) by purging freshwater with air for at least 30 minutes. The concentration of oxygen in the saturated solution was calculated using Unisense uSense Solutions software (https://unisense.com/product-category/software/) with temperature data from a Unisense temperature sensor. Duplicate measurements were collected in each core, which are recorded in the datafile, with duplicate measurements reported as two rows with the same core ID and sediment depth. Duplicates were either collected directly after the original measurement (within 40 - 62 seconds after the original measurement) or after the entire core had been measured (within 1.8 - 10.5 minutes after the original measurement). Duplicates taken directly after the original measurement have a relative percent different of less than 1.5 percent (n = 9), while duplicates recorded after the entire core was finished have a relative percent difference of less than 4.5 percent (n = 37). An oxygen concentration range from 0 to 330 micromolar oxygen (oxygen saturation in 2 degrees Celsius seawater) was considered reasonable for this dataset. Dataset is considered complete for the information presented, as described in the abstract. Data was collected at select intervals to record a complete profile of the entire core. Users are advised to read the rest of the metadata record carefully for additional details. The coordinates of the boxcores were derived from a 7000 m rated Ultrashort baseline (USBL) (Kongsberg MiniS 37-40V Ti) acoustic position where available, and the ships GPS position when not. For most of the boxcores, the boxcore lost contact with the USBL before hitting the bottom. For these cores, coordinates were calculated based on the midpoint between the deepest coordinates recorded on the USBL while the boxcore was lowered and the deepest coordinates recorded as it was recovered. For boxcore numbers 3, 4, 5, 17, and 25 the coordinates are recorded as the ship coordinates. For boxcore number 6 the coordinates are only the downcast USBL coordinates, and for boxcore 28 the coordinates are only the upcast USBL coordinates. For boxcore 38, the USBL recorded data at the bottom of the cast so the position where the boxcore reached the bottom is reported. The distance between the ship's position and the boxcore location at the seafloor calculated based on the midpoint of the USBL data is generally better than 50 meters. A formal accuracy assessment of the horizontal positional information in the dataset has not been conducted. The depth of the cores was recorded as the depth of the CTD attached to the top of the boxcore, plus two meters to compensate for the height of the boxcore. No formal positional accuracy tests were conducted. Abyssal sediment was collected using a boxcore deployed from the M/V Ocean Guardian between April 12 and April 30, 2026, during the 2026-604-FA American Samoa Critical Mineral and Mapping expedition lead by NOAA, BOEM, and USGS, and staffed by USGS employees. 20260413 A subcore with pre-drilled holes was collected from 35 boxcores using a mechanical subcoring device and piston that minimized sediment compaction. Within 2.5 hours of boxcore recovery and immediately after subcore recovery from boxcore, this push core was transferred to a cold laboratory van. The van maintained an average temperature of 5.6 degrees Celsius while microprofiling measurements occurred. 20260413 Oxygen microprofile measurements were completed shipboard in a cold laboratory van using Unisense oxygen microsensors (OX-100, OX-200, OX-NP) and Unisense uSense Solutions software (Unisense software). Oxygen microsensors were inserted through pre-drilled holes in the push core liner. Once the microsensor signal stabilized, the sediment depth associated with the measurement was recorded as a comment in the Unisense uSense software to generate a timestamp. 20260413 Results, location data, and sample information were combined into a comma-delimited text values document (2026_604_FA_oxygen.csv). 20260512 Katlin Adamczyk USGS Physical Scientist Mailing and Physical

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Santa Cruz CA 95060 831-460-7402 Kadamczyk@usgs.gov Point Point 560 0.0001 0.0001 Decimal degrees D_WGS_1984 WGS_1984 6378137.0 298.257223563 local sea surface height 1 meters Attribute values 2026_604_FA_oxygen.csv Comma-delimited file containing oxygen data for cores at provided depths and locations for the cores. Producer defined Core_ID The core ID for each subcore. Producer defined Core IDs are formatted as Cruise ID (2026_604_FA) _ boxcore ID (BX#) _ core number (PC#). Latitude This is the latitude of the sediment core. producer defined -17.0354 -13.1707 decimal degrees 0.0001 Longitude This is the longitude of the sediment core. producer defined -167.8617 -165.6202 decimal degrees 0.0001 Boxcore_depth_m This is the depth at which the sediment core was collected. producer defined 5184 5787 meters 1 Time_since_program_start_s The amount of time, in seconds, between the start of data collection and the associated measurement. producer defined 59.293 2681.603 seconds 0.001 Oxygen_uM_per_L The porewater oxygen concentration at the associated depth in the subcore. producer defined 157.6942 371.6118 micromole per liter 0.0001 Electrode_Type The type of electrode used for the associated measurement. Producer defined OX-100 Unisense OX-100 oxygen microsensor with a 90-110 micron tip diameter. producer defined OX-200 OX-100 oxygen microsensor with a 175-225 micron tip diameter. producer defined OX-NP Unisense OX-NP oxygen microsensor encased in a 1.6 by 40 mm steel piercing needle. producer defined Depth_cm The distance from the surface of the core to the location where the oxygen microsensor was inserted. producer defined 1 40 centimeters 1 Quality_code A numerical code denoting the confidence of the associated oxygen porewater measurement. Quality codes were assigned based on a visual interpretation of oxygen profiles and expected values. Values higher than the oxygen saturation at 2 degrees Celsius in seawater (330 uM/L) at the surface of the core were interpreted as being affected by oxygen diffusion during the time between sample recovery and oxygen measurement and were denoted with a quality code 3. Similarly, measurements at the bottom of the core that began to increase after the profile reached a minimum were marked with quality code 3 due to possible sediment disturbance and air introduction during subsampling. producer defined 1 Quality code 1 represents good quality data. producer defined 3 Quality code 3 represents unusual and anomalously high concentration, likely from the introduction of air during core subsampling at the bottom of the core or from oxygen diffusion through the top of the core. producer defined This dataset includes oxygen and positional data for cores contained in a single comma separated values file (2026_604_FA_oxygen.csv). The first line of the csv file is a header line. U.S. Geological Survey U.S. Geological Survey - CMGDS mailing and physical

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Santa Cruz CA 95060 831-427-4747 pcmsc_data@usgs.gov These data are available in .csv format contained in a single file. 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 USGS, no warranty expressed or implied is made regarding the display or utility of the data on any other system or for general or scientific purposes, nor shall the act of distribution constitute any such warranty. comma-delimited text Microsoft Excel 16.16.17 for Mac File contains table in .csv format No compression applied 0.066 https://doi.org/10.5066/P14JMPDV Data can be downloaded using the Network_Resource_Name link. None. These data can be viewed with Microsoft Excel or any text reader. 20260612 U.S. Geological Survey, Pacific Coastal and Marine Science Center PCMSC Science Data Coordinator mailing and physical

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Santa Cruz CA 95060 831-427-4747 pcmsc_data@usgs.gov Content Standard for Digital Geospatial Metadata FGDC-STD-001-1998