This data release provides geochemical, sedimentological, and geochronological data from interbedded fluvial and marsh deposits and radiocarbon dates of the section spanning the last 1500 years from the Pallett Creek paleoseismic site, California. The samples were collected to support paleoenvironmental reconstruction of the site and refine several previous investigations of paleoearthquakes along the San Andreas Fault (Sieh, 1978; Sieh, 1984; Sieh et al., 1989; Biasi and Weldon, 1994; Scharer et al., 2011). Geochemical and sedimentological data include grain size, magnetic susceptibility, dry bulk density, percent total organic matter, and percent total carbonate at contiguous 1 cm spacing and carbon (total C) to nitrogen (total N) ratios and charcoal counts every 4 cm from a 6.2 m section at the Pallett Creek paleoseismic site (34.4557°, -117.8872°). The data release also includes new and previously published radiocarbon datasets and associated depths to facilitate inter-study comparison. These datasets include: (1) New accelerator mass spectrometry (AMS) radiocarbon dates, completed in 2021 and 2022, targeting layers with few or conflicting dates in previous studies at the Pallett Creek paleoseismic site. For these samples, the types of taxa present in selected layers was determined. (2) AMS dates originally reported in Scharer et al. (2011) are included with amended d13C fractionation corrections and are assigned depths to the 6.2 m section at the Pallett Creek paleoseismic site. (3) Depths are assigned for conventional radiocarbon dates previously reported in Sieh (1978), Sieh et al. (1984), Sieh et al. (1989) and Biasi and Weldon (1994). The depth estimates enable use of the original studies with the newer stratigraphic and age data provided in the data release. (4) New radiocarbon dates from the same alluvial surface as the Pallett Creek paleoseismic site that are exposed ~1 km upstream (34.4536°, -117.8980°). This report should be used as the supplementary materials for any publication(s) that uses the sedimentologic and geochemical data or taxa identification or radiocarbon dates and depths reported herein. Revision 2.0 by Katherine M. Scharer on February 6, 2024. To review the changes that were made see 'Versioning.txt' file in the Attached Files section on the data release landing page.

This part of the data release is a spreadsheet including radiocarbon sample information and calibrated ages of sediment cores collected in 2014 from the northern flank of Monterey Canyon, offshore California. It is one of five files in this U.S. Geological Survey data release that include data from a set of sediment cores acquired from the continental slope, north of Monterey Canyon, offshore central California. Vibracores and push cores were collected with the Monterey Bay Aquarium Research Institute’s (MBARI’s) remotely operated vehicle (ROV) Doc Ricketts in 2014 (USGS cruise ID 2014-615-FA). One spreadsheet (NorthernFlankMontereyCanyonCores_Info.xlsx) contains core name, location, and length. One spreadsheet (NorthernFlankMontereyCanyonCores_MSCLdata.xlsx) contains Multi-Sensor Core Logger P-wave velocity and gamma-ray density whole-core logs of vibracores. One zipped folder of .bmp files (NorthernFlankMontereyCanyonCores_Photos.zip) contains continuous core photographs of the archive half of each vibracore. One spreadsheet (NorthernFlankMontereyCanyonCores_Radiocarbon.xlsx) contains radiocarbon sample information, results, and calibrated ages. One .pdf file (NorthernFlankMontereyCanyonCores_Figures.pdf) contains combined displays of data for each vibracore, including graphic diagram descriptive logs. This particular metadata file describes the information contained in the file NorthernFlankMontereyCanyonCores_Radiocarbon.xlsx. All vibracores are archived by the U.S. Geological Survey Pacific Coastal and Marine Science Center. Other remaining core material, if available, is archived at MBARI.

This part of the data release is a spreadsheet including radiocarbon sample information and calibrated ages of sediment cores collected in 2014 from the northern flank of Monterey Canyon, offshore California. It is one of five files in this U.S. Geological Survey data release that include data from a set of sediment cores acquired from the continental slope, north of Monterey Canyon, offshore central California. Vibracores and push cores were collected with the Monterey Bay Aquarium Research Institute’s (MBARI’s) remotely operated vehicle (ROV) Doc Ricketts in 2014 (USGS cruise ID 2014-615-FA). One spreadsheet (NorthernFlankMontereyCanyonCores_Info.xlsx) contains core name, location, and length. One spreadsheet (NorthernFlankMontereyCanyonCores_MSCLdata.xlsx) contains Multi-Sensor Core Logger P-wave velocity and gamma-ray density whole-core logs of vibracores. One zipped folder of .bmp files (NorthernFlankMontereyCanyonCores_Photos.zip) contains continuous core photographs of the archive half of each vibracore. One spreadsheet (NorthernFlankMontereyCanyonCores_Radiocarbon.xlsx) contains radiocarbon sample information, results, and calibrated ages. One .pdf file (NorthernFlankMontereyCanyonCores_Figures.pdf) contains combined displays of data for each vibracore, including graphic diagram descriptive logs. This particular metadata file describes the information contained in the file NorthernFlankMontereyCanyonCores_Radiocarbon.xlsx. All vibracores are archived by the U.S. Geological Survey Pacific Coastal and Marine Science Center. Other remaining core material, if available, is archived at MBARI.

Sediment cores were collected in Great Dismal Swamp National Wildlife Refuge in November, 2017 to advance understanding of climate- and land-management driven changes in vegetation, hydrology, and fire regimes. Radiocarbon dates were obtained from samples in two cores (GDS-519-3-21-2017 and GDS-520-3-21-2017) to generate age models for the cores. Bulk sediment samples, charcoal, plant macrofossils, and pollen residue were selected at the USGS in Reston, Virginia and submitted to Beta Analytic, Inc. and the National Ocean Sciences Accelerator Mass Spectrometry (NOSAMS) laboratories for radiocarbon dating. Those laboratories provided both radiocarbon ages and stable carbon isotope (delta 13C) results, which can be used to generate calibrated ages. Bulk density was measured for each core at the USGS in Reston, Virginia. Cores were sectioned at 1-cm increments. One cubic centimeter of wet sediment was extracted from each 1-cm increment downcore and weighed. Samples were subsequently dried at 100ºC for at least 24 hours to obtain dry weights, and bulk density was calculated by dividing original 1-cc volume by the dry weight. Polycyclic aromatic hydrocarbons (PAHs) and sedimentary charcoal were analyzed at the Virginia Institute of Marine Science at Gloucester Point, Virginia. PAH analysis began with freeze-drying of samples and extraction of their lipid contents using a Dionex 350 Accelerated Solvent Extractor (9:1; dicholoromethane:methanol). Total lipid extracts were separated into three fractions using silica gel columns and eluents of increasing polarity (F1: hexane, F2: 25% toluene in hexane, F3: methanol). Combined F1 and F2 fractions were analyzed to quantify PAHs using an Agilent 7890A gas chromatograph coupled with a 5975C mass selective detector (GC-MSD). The GC was equipped with a DB-5MS capillary column (30 m length; 320 µm outer diameter; 0.25 µm film thickness), which was heated using the following temperature program: 16 °C/minute to 150 °C and 5 °C/minute to 300 °C. Flow rate was 1.1 mL/minute. Individual PAH abundances were quantified using select ion monitoring mode (SIM) and relative to an external calibration curve constructed with a PAH calibration standard (Sigma-Aldrich CRM47940). Sixteen PAHs were quantified: naphthalene (Na), acenaphthylene (Ayl), acenaphthene (Ace), anthracene (An), phenanthrene (Phe), fluoranthene (Fla), pyrene (Py), benz[a]anthracene (Ba), chrysene (Ch), retene (Ret), benzo[k]fluoranthene (BkF), benzo[a]pyrene (BaP), benzo[b]fluoranthene (BbF), benzo[g,h,i]perylene (Bghi), dibenzo[a,h]anthracene (DiAn), and ideno[1,2,3-cd]pyrene (IP). PAH accumulation rates were quantified using the dry sediment concentration of PAHs and the age-depth model of the sediment cores. Sedimentary charcoal analysis followed a modified version of standard methodologies for isolating and identifying sedimentary charcoal particles. Dried sediment samples were weighed and then subjected to a light chemical treatment (1:1, by volume mixture of 1M sodium hexametaphosphate solution and 2% sodium hypochlorite solution) for 24 hours, in accordance with standard methods (Vachula et al., 2019, 2018). Samples were washed over two nested sieves (63 µm and 125 µm mesh sizes) to isolate an intermediate size fraction (63-125 µm), in which charcoal particles were enumerated using a dissection microscope and gridded petri dishes. Charcoal accumulation rates were quantified using the numeric concentration of charcoal particles, the bulk density of the sediments, and the age-depth model of the sediment cores. References Vachula, R.S., Russell, J.M., Huang, Y. and Richter, N., 2018. Assessing the spatial fidelity of sedimentary charcoal size fractions as fire history proxies with a high-resolution sediment record and historical data. Palaeogeography, Palaeoclimatology, Palaeoecology, 508, pp.166-175. Vachula, R.S., Russell, J.M. and Huang, Y., 2019. Climate exceeded human management as the dominant control of fire at the regional

This data release provides radiocarbon data for burned plant material collected from alluvial deposits following two wildfires in southern California. For the 2020 Bobcat Fire we collected deposits in five stream channels within the Pallett Creek drainage in 2021. For the 2013 Grand Fire near Frazier Mountain, we sampled from two shallow pits excavated into alluvium deposited in 2014. The types of taxa present at each sample location were identified and radiocarbon samples were selected based on the types of material present. This report should be used as the supplementary materials for any publication(s) that uses the radiocarbon dates or taxa identification reported herein.

This part of the data release is a spreadsheet including radiocarbon sample information and calibrated ages of sediment cores collected in 2009 offshore of Palos Verdes, California. It is one of seven files included in this U.S. Geological Survey data release that include data from a set of sediment cores acquired from the continental slope, offshore Los Angeles and the Palos Verdes Peninsula, adjacent to the Palos Verdes Fault. Gravity cores were collected by the USGS in 2009 (cruise ID S-I2-09-SC; http://cmgds.marine.usgs.gov/fan_info.php?fan=SI209SC), and vibracores were collected with the Monterey Bay Aquarium Research Institute's remotely operated vehicle (ROV) Doc Ricketts in 2010 (cruise ID W-1-10-SC; http://cmgds.marine.usgs.gov/fan_info.php?fan=W110SC). One spreadsheet (PalosVerdesCores_Info.xlsx) contains core name, location, and length. One spreadsheet (PalosVerdesCores_MSCLdata.xlsx) contains Multi-Sensor Core Logger P-wave velocity, gamma-ray density, and magnetic susceptibility whole-core logs. One zipped folder of .bmp files (PalosVerdesCores_Photos.zip) contains continuous core photographs of the archive half of each core. One spreadsheet (PalosVerdesCores_GrainSize.xlsx) contains laser particle grain size sample information and analytical results. One spreadsheet (PalosVerdesCores_Radiocarbon.xlsx) contains radiocarbon sample information, results, and calibrated ages. One zipped folder of DICOM files (PalosVerdesCores_CT.zip) contains raw computed tomography (CT) image files. One .pdf file (PalosVerdesCores_Figures.pdf) contains combined displays of data for each core, including graphic diagram descriptive logs. This particular metadata file describes the information contained in the file PalosVerdesCores_Radiocarbon.xlsx. All cores are archived by the U.S. Geological Survey Pacific Coastal and Marine Science Center.

This data release contains data from cores collected in marshes and in sediments under invasive Brazilian waterweed (Egeria densa Planchon) in the Sacramento-San Joaquin Delta of California during the spring of 2018. Data are provided in two text files in comma separated columns. The first Core_Sites_Details.txt contains core site location, collection dates, and naming information. The second file, Core_Section_Analyses.txt contains % organic carbon, % inorganic sediment, bulk density data for each 2-cm section of six peat cores collected in marshes and six sediment cores collected under patches of Brazilian waterweed. Additionally, the second file contains the radioisotope values (137Cs and 210Pb) for each of the cores. Cores were collected at three Delta study sites: Lindsey Slough, Mokelumne River, and Middle River in the Delta.

Results of radiocarbon age dating of planktic foraminifera, benthic foraminifera, and pelecypod shell fragments collected from piston cores, trigger weight cores, and IKU grab samples obtained in 2015 and 2017 offshore British Columbia, Canada and southeastern Alaska, U.S. along the Queen Charlotte-Fairweather fault zone.

Results of radiocarbon age dating of planktic foraminifera, benthic foraminifera, and pelecypod shell fragments collected from piston cores, trigger weight cores, and IKU grab samples obtained in 2015 and 2017 offshore British Columbia, Canada and southeastern Alaska, U.S. along the Queen Charlotte-Fairweather fault zone.

This dataset includes tables of radiocarbon, uranium thorium series, and luminescence geochronologic ages and stable carbon and oxygen isotope compositions for sedimentary and organic samples.