Grant D. Colip Peter G. Chirico Alexandra K. Lair Julia L. Seidenstein 20250922 spreadsheet https://doi.org/10.5066/P13HGVV2 This data release presents multi-proxy geochemical and sedimentological data from 20 short sediment cores (ranging 50–70 cm in depth) collected in 2003 along the Euphrates, Tigris, and Shatt al-Gharraf rivers in the Lower Mesopotamian Plain, Iraq. The dataset includes X-ray fluorescence (XRF) elemental abundances, particle size distributions, visible and near-infrared spectrophotometry data, and magnetic susceptibility measurements, along with line-scan images of the cores. These cores were collected to investigate modern floodplain dynamics, sedimentary processes, and irrigation-related depositional signatures in an arid to semi-arid environment that has been shaped by millennia of river management, agriculture, and land use. The data are structured to support geomorphological, paleoenvironmental, and geoarchaeological research on sediment sources, hydrologic regimes, and stratigraphic changes across southern Iraq. The data presented here were collected in 2024-2025 at the USGS Florence Bascom Geoscience Center (FBGC) in Reston, VA. Multi-sensor core logger data and line-scan images were collected using instrumentation housed in the Bascom Multi-Sensor Core Logger (BASCORE) Laboratory, and particle size distribution data were collected in the Bascom Laser Diffraction Sedimentology Laboratory. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. The sediment analysis data collected in this study will be used to enhance our understanding of recent and historic sedimentation processes in the lower Mesopotamian Plain. These insights support geomorphological interpretations of floodplain evolution, inform studies of irrigation and land use dynamics, and contribute to geoarchaeological investigations of human-environment interactions in a highly modified landscape. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. 20030810 20030821 ground condition Complete None planned 44.3570 46.1870 32.9980 31.3310 ISO 19115 Topic Category geoscientificInformation None U.S. Geological Survey USGS Florence Bascom Geoscience Center FBGC particle size analysis grain size Iraq magnetic susceptibility sedimentology color reflectance geochemistry elemental XRF pXRF X-ray fluorescence sediment core floodplain geomorphology alluvial sedimentation irrigation Holocene geoarchaeology multi-proxy core logging USGS Thesaurus Geochemistry Geography Geomorphology Sedimentology Soil Sciences USGS Metadata Identifier USGS:68ae0ee9d4be02406c8cf1d6 None Mesopotamian Plain Iraq Mesopotamia Shatt al-Gharraf Tigris Euphrates None. Please see 'Distribution Info' for details. None. Users are advised to read the dataset's metadata thoroughly to understand appropriate use and data limitations. Grant D. Colip U.S. Geological Survey; Florence Bascom Geoscience Center Physical Scientist mailing and physical

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Reston Virginia 20192 United States (703) 648-6919 (703) 648-6953 Field and preliminary lab work was supported by the USGS Earth Surface Processes Team and the Mineral Resources Team in 2005. Subsequent analysis was conducted in 2024–2025 by staff at the Florence Bascom Geoscience Center, including the BASCORE (Bascom Multi-Sensor Core Logger) and BLAZER (Bascom Laser Diffraction Sedimentology) laboratories. Cores were collected in cooperation with the U.S. Marine Engineering Group (MEG) during post-conflict reconstruction work in Iraq. This work was funded by the U.S. Army Night Vision and Electronic Sensors Directorate, S&T Division, Signal & Image Processing Branch, and the U.S. Geological Survey's National Geological and Geophysical Data Preservation Program. These data have been peer reviewed and assessed for accuracy using processes described in the Process Step section of this metadata. Data values from each analysis were checked to ensure that they fall within the expected ranges. Data were checked for duplication and omission. No other formal logical consistency reports were conducted. The dataset is considered complete for the information presented, as described in the abstract. Users are advised to read the rest of the metadata record carefully for additional details. No formal positional accuracy tests were conducted. No formal positional accuracy tests were conducted. Twenty sediment cores were originally collected between August 10-21, 2003, by a team from the U.S. Marine Engineering Group (MEG) in cooperation with the U.S. Geological Survey (USGS). These cores were acquired during post-conflict reconstruction efforts in central Iraq, with site selection focused on locations accessible by road and situated adjacent to river channels or irrigation networks. The intent of the original collection was to support geotechnical and hydrological assessments relevant to transportation infrastructure and environmental management projects across the Lower Mesopotamian Plain. Each core was extracted using PVC tubes approximately 3 inches (7.6 cm) in diameter, with core lengths ranging between 50 and 70 cm. Upon recovery, cores were split lengthwise into archive and working halves. The archive halves were sealed, labeled, and stored under climate-controlled conditions, while the working halves were reserved for subsequent analysis. 20030821 Peter G. Chirico U.S. Geological Survey; Florence Bascom Geoscience Center Supervisory Geographer mailing and physical

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Reston Virginia 20192 United States (703) 648-6950 (703) 648-6953 pchirico@usgs.gov In 2024, non-destructive core imaging and logging was conducted at the Bascom Multi-Sensor Core Logger (BASCORE) Laboratory in Reston, Virginia using a suite of GeoTek multi-sensor core loggers (MSCL-S and MSCL-XZ). Measurements for X-ray fluorescence (XRF), magnetic susceptibility, and visible and near-infrared spectrophotometry were collected at 0.5 cm resolution along the split surface of each core. High-resolution line-scan images were also produced for each split core surface. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. 20240918 Julia L. Seidenstein U.S. Geological Survey; Florence Bascom Geoscience Center Geologist mailing and physical

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Reston Virginia 20192 United States (703) 648-6151 (703) 648-6953 jseidenstein@usgs.gov In 2025, the working halves of each core were subsampled at 5 cm intervals for laser diffraction particle size analysis (PSA) in the Bascom Laser Diffraction Sedimentology Laboratory. Analyses were completed using a Beckman Coulter LS 13 320 XR instrument, which measures grain-size distributions ranging from <0.04 µm (clay) to >2,000 µm (coarse sand) and produces high-resolution quantitative data on sediment texture. Due to their dessicated nature, samples were soaked in 0.5% sodium hexametaphosphate (deflocculant) for a minimum of 24 hours prior to analysis. Samples were then sonicated in an ultrasonic bath for approximately 30 seconds, gently agitated with a 5 mL transfer pipette, and immediately loaded into the LS XR equipment. Each sample underwent three runs of 90 s duration each, from which the averages were reported. The resultant particle size distributions were checked for logical consistency across the runs, and in some cases samples were re-run to ensure consistency and accuracy of the data produced. Contact the authors of this dataset for more details about the parameters for this analysis. Data are presented as raw (unaltered) outputs. Variation in the number of significant digits reported between some samples is a result of the instrument output and should not be intepreted as an indicator of precision. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. 20250530 Grant D. Colip U.S. Geological Survey; Florence Bascom Geoscience Center Physical Scientist mailing and physical

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Reston Virginia 20192 United States (703) 648-6919 (703) 648-6953 gcolip@usgs.gov Comma separated value files containing MSCL data (Iraq_MSCL_data.csv), particle size inventory (Iraq_PSA_inventory.csv), particle size data (Iraq_PSA_data.csv), and particle size statistics (Iraq_PSA_statistics.csv) are described in a data dictionary rather than directly in this metadata file. A .zip folder (Iraq_MSCL_images.zip) contains the line-scan core images from the MSCL. The files are as follows: - Iraq_MSCL_data.csv, which includes the raw data from MSCL including X-ray fluorescence, spectrophotometry, and magnetic susceptibility; - Iraq_MSCL_images.zip, which contains the line-scan images of the sediment cores; - Iraq_PSA_and_core_inventory.csv, which includes inventory for the sediment cores and the particle size analysis subsamples; - Iraq_PSA_data.csv, which includes the raw data from laser diffraction particle size analysis, - Iraq_PSA_statistics.csv, which includes statistics from laser diffraction particle size analysis, - Iraq_DataDictionary.csv, which is a data dictionary describing the data in the other .csv files. Iraq_MSCL_data.csv Iraq_MSCL_images.zip Iraq_PSA_data.csv Iraq_PSA_statistics.csv Iraq_PSA_and_core_inventory.csv Iraq_DataDictionary.csv GS ScienceBase U.S. Geological Survey mailing address

Denver Federal Center, Building 810, Mail Stop 302

Denver CO 80225 United States 1-888-275-8747 sciencebase@usgs.gov 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. Digital Data https://doi.org/10.5066/P13HGVV2 None 20250922 Grant D. Colip U.S. Geological Survey; Florence Bascom Geoscience Center Physical Scientist mailing and physical

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Reston Virginia 20192 United States (703) 648-6919 (703) 648-6953 gcolip@usgs.gov FGDC Content Standard for Digital Geospatial Metadata FGDC-STD-001-1998