210Pb and 137Cs measurements from core 721-1 obtained in 2002 off San Francisquito Creek in South San Francisco Bay

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Frequently anticipated questions:

What does this data set describe?

Title:
210Pb and 137Cs measurements from core 721-1 obtained in 2002 off San Francisquito Creek in South San Francisco Bay
Abstract:
This data release provides 210Pb and 137Cs measurements in sediments of a core obtained off San Francisquito Creek in South San Francisco Bay.
Supplemental_Information:
Additional information about the field activity from which these data were derived is available online at: https://cmgds.marine.usgs.gov/fan_info.php?fan=2002-603-DD Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
  1. How might this data set be cited?
    McGann, Mary, and Lorenson, Thomas D., 20230828, 210Pb and 137Cs measurements from core 721-1 obtained in 2002 off San Francisquito Creek in South San Francisco Bay: data release DOI: 10.5066/P9QQT6KZ, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, California.

    Online Links:

    This is part of the following larger work.

    McGann, Mary, Starratt, Scott W., Reidy, Liam M., Lorenson, Thomas D., Phillips, R. Lawrence, and Kneeshaw, Tara A., 2023, Radiocarbon measurements, census counts of benthic foraminifera, diatoms, and palynomorphs, and geochemistry from core 721-1 obtained in 2002 off San Francisquito Creek in South San Francisco Bay: data release DOI:10.5066/P9QQT6KZ, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, CA.

    Online Links:

    Other_Citation_Details:
    Suggested Citation: McGann, M., Starratt, S.W., Reidy, L., Lorenson, T.D., Phillips, R.L., and Kneeshaw, T.A., 2023, Radiocarbon measurements, census counts of benthic foraminifera, diatoms, and palynomorphs, and geochemistry from core 721-1 obtained in 2002 off San Francisquito Creek in South San Francisco Bay: U.S. Geological Survey data release, https://doi.org/10.5066/P9QQT6KZ.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -122.0961
    East_Bounding_Coordinate: -122.0961
    North_Bounding_Coordinate: 37.4583
    South_Bounding_Coordinate: 37.4583
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 2002
    Ending_Date: 2023
    Currentness_Reference:
    Ground condition at time data were collected.
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: comma-delimited text
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      This is a Point data set. It contains the following vector data types (SDTS terminology):
      • Point (28)
    2. What coordinate system is used to represent geographic features?
      Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 0.0001. Longitudes are given to the nearest 0.0001. Latitude and longitude values are specified in Decimal degrees. The horizontal datum used is North American Datum of 1927.
      The ellipsoid used is Clarke 1866.
      The semi-major axis of the ellipsoid used is 6378206.4.
      The flattening of the ellipsoid used is 1/294.978698214.
  7. How does the data set describe geographic features?
    A comma-separated values file with the first line being a header line.
    Results of radiocarbon dating, benthic foraminiferal census counts, diatom census counts, palynomorph census counts, and metal content of fine sediment. (Source: Producer defined.)
    Date_Collected
    Date in year. (Source: Producer defined.)
    Range of values
    Minimum:2002
    Maximum:2002
    Latitude
    Latitude of the site at which the push core was collected. (Source: Producer defined.)
    Range of values
    Minimum:37.4583
    Maximum:37.4583
    Units:decimal degrees
    Resolution:0.0001
    Longitude
    Longitude of the site at which the push core was collected. (Source: Producer defined.)
    Range of values
    Minimum:-122.0961
    Maximum:-122.0961
    Units:decimal degrees
    Resolution:0.0001
    Sample_Upper_Depth_Limit_cm
    The upper depth at which the sediment sample was obtained below the sediment surface in a core. (Source: Producer defined.)
    Range of values
    Minimum:1
    Maximum:112
    Units:centimeters
    Resolution:1
    Sample_Lower_Depth_Limit_cm
    The lower depth at which the sediment sample was obtained below the sediment surface in a core. (Source: Producer defined.)
    Range of values
    Minimum:2
    Maximum:113
    Units:centimeters
    Resolution:1
    Dry_Bulk_Density_per_cubic_g
    Measurement of the density of bulk dry sediment per cubic gram. (Source: Producer defined.)
    Range of values
    Minimum:1.1277
    Maximum:1.8385
    Units:per cubic gram
    Resolution:0.0001
    Cumulative_Mass_g_per_square_cm
    Measurement of the cumulative mass of the sediment in grams per square centimeter. (Source: Producer defined.)
    Range of values
    Minimum:1.4554
    Maximum:40.7576
    Units:grams per square centimeter
    Resolution:0.0001
    Total_210Pb_dpm_per_g
    Measurement of the total 210Pb in disintegrations per minute per gram of sediment. (Source: Producer defined.)
    Range of values
    Minimum:1.2607
    Maximum:5.4047
    Units:disintegrations per minute per gram
    Resolution:0.0001
    226Ra_dpm_per_g
    Measurement of 226Ra in disintegrations per minute per gram of sediment. (Source: Producer defined.)
    Range of values
    Minimum:0.8284
    Maximum:1.7553
    Units:disintegrations per minute per gram
    Resolution:0.0001
    226Ra_Error_dpm_per_g
    Error in the measurement of 226Ra in disintegrations per minute per gram of sediment. (Source: Producer defined.)
    Range of values
    Minimum:0.1224
    Maximum:0.2891
    Units:disintegrations per minute per gram
    Resolution:0.0001
    Excess_210Pb_dpm_per_g
    Measurement of the excess 210Pb in disintegrations per minute per gram of sediment. (Source: Producer defined.)
    Range of values
    Minimum:0.1586
    Maximum:4.1482
    Units:disintegrations per minute per gram
    Resolution:0.0001
    Excess_210Pb_Error_dpm_per_g
    Measurement of the error in the excess 210Pb in disintegrations per minute per gram of sediment. (Source: Producer defined.)
    Range of values
    Minimum:0.4972
    Maximum:1.1223
    Units:disintegrations per minute per gram
    Resolution:0.0001
    137Cs_dpm_per_g
    Measurement of the 137Cs in disintegrations per minute per gram of sediment. (Source: Producer defined.)
    Range of values
    Minimum:0
    Maximum:0.5196
    Units:disintegrations per minute per gram
    Resolution:0.0001
    137Cs_Error_dpm_per_g
    Measurement of the error of 137Cs in disintegrations per minute per gram of sediment. 9999 represents no data. (Source: Producer defined.)
    Range of values
    Minimum:0.0166
    Maximum:0.2079
    Units:disintegrations per minute per gram
    Resolution:0.0001
    Linear_Sedimentation_Rate_cm_per_year
    The linear sedimentation rate in centimeters of sediment per year. 9999 represents no data. (Source: Producer defined.)
    Range of values
    Minimum:0.9494
    Maximum:34.3484
    Units:centimeters per year
    Resolution:0.0001
    Mass_Accumulation_Rate_mg_per_squared_cm_per_year
    The mass accumulation rate in milligrams per squared centimeter of sediment per year. (Source: Producer defined.)
    Range of values
    Minimum:424.0040
    Maximum:11110.0597
    Units:milligrams per squared centimeter per year
    Resolution:0.0001
    Entity_and_Attribute_Overview:
    The first line of the comma-separated values file is a header line.
    Entity_and_Attribute_Detail_Citation: U.S. Geological Survey

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Mary McGann
    • Thomas D. Lorenson
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
    U.S. Geological Survey, Pacific Coastal and Marine Science Center
    Attn: PCMSC Science Data Coordinator
    2885 Mission Street
    Santa Cruz, CA

    650-329-4979 (voice)
    pcmsc_data@usgs.gov

Why was the data set created?

The urbanized area of downtown Menlo Park is subject to persistent flooding and sediment deposition by San Francisquito Creek in South San Francisco Bay. To mitigate these events, a suite of cores was collected in 2002 at the mouth of the creek to determine sediment depositional rates on the delta. One of those cores was selected for microbiological (pollen, diatoms, and foraminifera) and geochemical analyses to reconstruct a depositional record over the past two millennia. Based on an abrupt change in lithology and faunal assemblages, an instantaneous vertical displacement and deepening of the depositional environment is evident. Coseismic subsidence associated with large fault ruptures may cause these events. An age model based on the first appearances of non-indigenous biota, radiocarbon dates, radiochemistry, and sediment geochemistry suggests the 1868 rupture of the Hayward Fault may have been the cause.

How was the data set created?

  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
    Date: 2002 (process 1 of 2)
    A metal core barrel, approximately 9 cm in diameter, was driven into the mudflat slightly northwest of Hooks Point on informally named "Hooks Island" in South San Francisco Bay near Palo Alto, California in 2002 to recover a sediment core. The precise coring location is not available. The core was brought to the the USGS facility in Menlo Park, California and housed in a core refrigerator.
    Date: 2022 (process 2 of 2)
    Twenty-eight sediment samples from core 721-1 were prepared for 210Pb and 137Cs following the methods of Swarzenski and others (2006) and Swarzenski (2014). Samples weighing 15-20 grams were taken every 2 cm continuously down through 20 cm and then approximately every 5 cm to a depth of 113 cm. Sediment samples for 210Pbc dating were weighed before and after drying at 105 degrees celsius for at least 24 hours, disaggregated in a mortar and pestle, transferred to a plastic test tube, then placed in a gamma radiation detector and counted. Total 210Pb activities were directly determined by measuring the 46.52-KeV gamma peak using ORTEC High Purity Germanium (HPGe) radiation detectors. Supported levels of 210Pb from 226Ra were determined by measuring the gamma activity of 214Pb (at 295 and 352 KeV) and of 214Bi (609 KeV), the short-lived daughter products of 226Ra (351.87 and 609.31 KeV). 137Cs activities in this study were determined by measurement of the 661.6-KeV gamma peak. Precision in these measurements was less than 5 percent.
  3. What similar or related data should the user be aware of?
    Swarzenski, P.W., Baskaran, M., Rosenbauer, R.J., and Orem, W.H., 2006, Historical trace element distribution in sediments from the Mississippi River Delta..

    Online Links:

    Other_Citation_Details:
    Swarzenski, P.W., Baskaran, M., Rosenbauer, R.J., and Orem, W.H., 2006, Historical trace element distribution in sediments from the Mississippi River Delta: Estuaries and Coasts, v. 29. p. 1094-1107.
    Swarzenski, P.W., 2014, 210Pb dating..

    Online Links:

    Other_Citation_Details:
    Swarzenski, P.W., 2014, 210Pb dating, in Rink, W., Thompson, J., eds., Encyclopedia of Scientific Dating Methods, Springer, Dordrecht, p. 1-11.

How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?
    Because of the inverse relationship between particle surface area and particle size, the finest sediment available was analyzed. The thinnest possible sediment layers were sampled to provide better time resolution of sedimentation rates. NIST radioactive spikes and material and International Atomic Energy Agency (IAEA) radioactive standards were used for calibrating the counting equipment. Precision in the activities of 210Pb and 226Ra was typically better than 5 percent. Since our spikes are primary standards and our counting equipment was well calibrated, our accuracy was similar to our precision.
  2. How accurate are the geographic locations?
    A formal accuracy assessment of the horizontal positional information in the data set has not been conducted. The horizontal position was estimated based on distances from the modern tidal channel listed on a figure provided to the first author in October 2003. The horizontal accuracy cannot be determined.
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
    Dataset is considered complete for the information presented, as described in the abstract. Users are advised to read the metadata for each part of this data release carefully for additional details.
  5. How consistent are the relationships among the observations, including topology?
    Data were checked for logical consistency by the laboratory staff before release to confirm that numerical values were not outside a reasonable range for a particular field.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints None
Use_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. Please recognize and acknowledge the U.S. Geological Survey as the originators of the dataset and in products derived from these data.
  1. Who distributes the data set? (Distributor 1 of 1)
    U.S. Geological Survey - ScienceBase
    Denver Federal Center, Building 810, Mail Stop 302
    Denver, CO

    1-888-275-8747 (voice)
    sciencebase@usgs.gov
  2. What's the catalog number I need to order this data set? These data are available in a comma-delimited text file (SFC_210Pb_137Cs_data.csv) which contains results from 210Pb and 137Cs measurements from core 721-1 obtained in 2002 off San Francisquito Creek in South San Francisco Bay.
  3. What legal disclaimers am I supposed to read?
    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 on any other system or for general or scientific purposes, nor shall the act of distribution constitute any such warranty.
  4. How can I download or order the data?
  5. What hardware or software do I need in order to use the data set?
    These data can be viewed with any text editor software.

Who wrote the metadata?

Dates:
Last modified: 28-Aug-2023
Metadata author:
U.S. Geological Survey, Pacific Coastal and Marine Science Center
Attn: PCMSC Science Data Coordinator
2885 Mission Street
Santa Cruz, CA

831-427-4747 (voice)
pcmsc_data@usgs.gov
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)
This page is <https://cmgds.marine.usgs.gov/catalog/pcmsc/DataReleases/ScienceBase/DR_P9QQT6KZ/SFC_210Pb_137Cs_metadata.faq.html>
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