Local radiocarbon reservoir age (ΔR) variability from the nearshore and open-ocean environments of the Florida Keys reef tract during the Holocene and associated U-series and radiocarbon data (Marine20 Radiocarbon Calibration Curve)

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Frequently anticipated questions:

What does this data set describe?

Title:
Local radiocarbon reservoir age (ΔR) variability from the nearshore and open-ocean environments of the Florida Keys reef tract during the Holocene and associated U-series and radiocarbon data (Marine20 Radiocarbon Calibration Curve)
Abstract:
68 Holocene-aged corals from reef cores collected throughout the Florida Keys reef tract (FKRT) were dated using a combination of U-series and radiocarbon techniques to quantify the millennial-scale variability in the local radiocarbon reservoir age (ΔR) of the shallow water environments of south Florida. ΔR provides a measure of the deviation of local radiocarbon concentrations of marine environments from the global average and can be used as a tracer of oceanic circulation and local hydrology. U.S. Geological Survey (USGS) scientists combined coral-based estimates of ΔR, using statistical modeling, to reconstruct millennial-scale variability in ΔR at locations on the FKRT with (“nearshore”) and without (“open ocean”) terrestrial influence. USGS scientists also used the models to provide temporally-explicit estimates of ΔR that can be used in radiocarbon calibrations of marine samples from the region. In Version 1.0 of the USGS data release (Toth and others, 2017) associated with this metadata record, derivedthe coral-based estimates of ΔR were derived using data from the Marine13 radiocarbon calibration curve (Reimer and others, 2013). In version 2.0, the ΔR estimates were instead derived using the Marine20 radiocarbon calibration curve (Heaton and others, 2020). For further information regarding data collection and analysis methods refer to Toth and others (2017).
  1. How might this data set be cited?
    Toth, Lauren T., Cheng, Hai, Edwards, R. Lawrence, Ashe, Erica, and Richey, Julie N., 20210830, Local radiocarbon reservoir age (ΔR) variability from the nearshore and open-ocean environments of the Florida Keys reef tract during the Holocene and associated U-series and radiocarbon data (Marine20 Radiocarbon Calibration Curve):.

    This is part of the following larger work.

    Toth, Lauren T., Cheng, Hai, Edwards, R. Lawrence, Ashe, Erica, and Richey, Julie N., 20170907, Local radiocarbon reservoir age (ΔR) variability from the nearshore and open-ocean environments of the Florida Keys reef tract during the Holocene and associated U-series and radiocarbon data: U.S. Geological Survey data release doi:10.5066/F7P8492Q, U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center, St. Petersburg, Florida.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -82.92
    East_Bounding_Coordinate: -80.0967
    North_Bounding_Coordinate: 25.5906
    South_Bounding_Coordinate: 24.45
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 01-Jan-1991
    Ending_Date: 15-Jun-2021
    Currentness_Reference:
    Date range of U-series and radiocarbon analysis and modeling
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: Tabular digital data
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
    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 0.0198058733. Longitudes are given to the nearest 0.0217155309. Latitude and longitude values are specified in Decimal degrees. The horizontal datum used is D_North_American_1983.
      The ellipsoid used is GRS_1980.
      The semi-major axis of the ellipsoid used is 6378137.0.
      The flattening of the ellipsoid used is 1/298.25722101.
  7. How does the data set describe geographic features?
    FKRT_Coral_Based_DeltaR_Marine20
    ΔR estimates for the 68 corals from the FKRT, description of those coral samples, sample locations, and summary of data used to calculate ΔR. (Source: Sample information and DeltaR values: Lauren T. Toth (USGS-SPCMSC); U-series data: Hai Cheng (Xi’an Jiaotong University, China), R. Lawrence Edwards (University of Minnesota); Radiocarbon data: John McGeehin (USGS Radiocarbon Laboratory), Lawrence Livermore National Laboratories Center for Accelerator Mass Spectrometry, University of California, Davis Stable Isotope Laboratory, Beta Analytic, Inc., and Geochron Laboratories; Marine20 data: http://intcal.org/curves/marine20.14c.)
    Sample ID
    Unique identifier for each coral sample dated in this study. (Source: USGS) Sample IDs are generated by abbreviating information about the region, site, core, and approximate water depth from which each sample was collected and are formatted as: Region abbreviation-Site abbreviation-Core number-Depth of coral in core.
    Latitude
    The approximate latitude, in NAD83 coordinates, where the core containing the coral sample was collected. (Source: USGS)
    Range of values
    Minimum:24.4500
    Maximum:25.5906
    Units:Decimal degrees
    Longitude
    The approximate longitude, in NAD83 coordinates, where the core containing the coral sample was collected. (Source: USGS)
    Range of values
    Minimum:-82.92
    Maximum:-80.0967
    Units:Decimal degrees
    Site
    Site name where the core containing the coral sample was collected. (Source: USGS) The name of the reef or group of reefs where the core containing the sample was collected.
    Subregion
    The subregion of the Florida Keys reef tract where the core containing the sample was collected. (Source: USGS)
    ValueDefinition
    Dry Tortugas N.P.The westernmost subregion of the Florida Keys reef tract located within the boundaries of Dry Tortugas National Park.
    MarquesasThe subregion of the Florida Keys reef tract located between Dry Tortugas National Park and the Lower Keys.
    Lower KeysThe subregion of the Florida Keys reef tract located between the Marquesas and the Middle Keys.
    Middle KeysThe subregion of the Florida Keys reef tract located between the Lower Keys and the Upper Keys.
    Upper KeysThe subregion of the of the Florida Keys reef tract located between the Middle Keys and the Biscayne National Park.
    Biscayne N.P.The northernmost subregion of the Florida Keys reef tract located within the boundaries of Biscayne National Park.
    Coral genus
    The genus of the coral sample. (Source: World Register of Marine Species: http://www.marinespecies.org/)
    ValueDefinition
    OrbicellaThe coral genus containing the species O. faveolata, O. franksii, and O. annularis.
    AcroporaThe coral genus containing the species A. palmata and A. cervicornis.
    DiploriaThe coral genus containing the species D. strigosa, D. clivosa, and D. labyrinthiformis.
    MontastraeaThe coral genus containing the species M. cavernosa.
    ColpophylliaThe coral genus containing the species C. natans.
    230Th Age (years BP)
    Holocene 230Th (U-series) age of the coral sample used as age of the sample before present (where present is 1950) when calculating the local reservoir age, ΔR. The age has been corrected based on the assumption that the initial 230Th/232Th atomic ratio is 4.4 ± 2.2 x10-6: the value for a material at secular equilibrium, with the bulk earth 232Th/238U value of 3.8. (Source: USGS)
    Range of values
    Minimum:41
    Maximum:10242
    Units:Years before present (where present is 1950)
    230Th age error (2 SE)
    The 2-standard error (2 SE) analytical uncertainty of the 230Th age. (Source: USGS)
    Range of values
    Minimum:6
    Maximum:55
    Units:years
    Conventional 14C age (years)
    The 14C age of the sample corrected for the fractionation of 13C, but not calibrated against the Marine13 calibration curve. (Source: USGS)
    Range of values
    Minimum:380
    Maximum:9485
    Units:years
    14C age error (1 SE)
    The 1-standard error (1 SE) analytical uncertainty of the conventional radiocarbon (14C) age. (Source: USGS)
    Range of values
    Minimum:20
    Maximum:70
    Units:years
    Marine20 14C age (years)
    The predicted 14C age of the sample from the marine calibration curve (Marine20; Heaton and others 2020; http://intcal.org/curves/marine20.14c), using the corrected 230Th age as age before present (cal BP) of the sample. (Source: USGS)
    Range of values
    Minimum:608
    Maximum:9573
    Units:years
    Marine20 14C age error (1 SE)
    The 1-standard error (1 SE) uncertainty associated with the modeled 14C ages of the Marine20 calibration curve. (Source: USGS)
    Range of values
    Minimum:56
    Maximum:70
    Units:years
    Delta-R (years)
    ΔR (Delta-R) values (in years) calculated by subtracting the predicted radiocarbon age of the sample from the marine calibration curve (Marine20 14C age), from the conventional radiocarbon age of that sample (Conventional 14C age). (Source: USGS)
    Range of values
    Minimum:-806
    Maximum:207
    Units:years
    Delta-R error (1 SE)
    The 1-standard error (1 SE) uncertainty associated with the estimates of ΔR (Delta-R). Calculated as the root-mean-square of the error associated with the conventional 14C age of the sample (14C age error) and the error associated with the predicted 14C age from the marine calibration curve (Marine20 14C age error). (Source: USGS)
    Range of values
    Minimum:61
    Maximum:92
    Units:years
    Data included in statistical models? (Y/N)
    An identifier to indicate whether the data were included in the subset used in the statistical models of ΔR variability. (Source: USGS)
    ValueDefinition
    YY=yes the data were included in the statistical models.
    NN=no the data were not included in the statistical models for the reasons outlined in Toth and others (2017).
    Model name
    Identifies which model of Delta-R the data were included in: nearshore or open ocean. This attribute is coded as "None" if data were not included in statistical models. (Source: USGS)
    ValueDefinition
    NearshoreIndicates that the data point was included in the nearshore model of Delta-R.
    Open OceanIndicates that the data point was included in the open-ocean model of Delta-R.
    NoneIndicates that the data point was not included in any statistical model.
    Modeled_OpenOcean_DeltaR_vs_230Th_Marine20
    Statistical model output of open-ocean ΔR variability from 8,000 years BP to present with a 5-year time step using 230Th age to derive age before present. All statistical analyses were conducted using MATLAB ® software (v. 9.1). (Source: Sample information and DeltaR values: Lauren T. Toth (USGS-SPCMSC); Statistical model: Erica Ashe (Rutgers University).)
    230Th Age (years BP)
    Age before present (modeled from corrected 230Th age before present) from 8000-0 years before present (where present is 1950 C.E.) with a time step of 5 years. (Source: USGS)
    Range of values
    Minimum:0
    Maximum:8000
    Units:years before present (where present is 1950 C.E.)
    Delta-R (14C years)
    Predicted (modeled) ΔR (Delta-R) values (in radiocarbon [14C] years) for every 5 years before present over the range of 8000-0 years before present. (Source: USGS)
    Range of values
    Minimum:-321.94787
    Maximum:-117.024319
    Units:14C years
    Delta-R error (1 SE)
    The 1-standard error (1 SE) uncertainty associated with predicted (modeled) ΔR (Delta-R) values (in years) for every 5 years before present over the range of 0-8000 years before present. (Source: USGS)
    Range of values
    Minimum:16.902595
    Maximum:31.34312
    Units:14C years
    Modeled_OpenOcean_DeltaR_vs_Conventional_14C_Marine20
    Modeled predictions of ΔR for open-ocean locations in south Florida over the range of conventional radiocarbon ages from 7,500 years ago to present with a 5-year time step. All statistical analyses were conducted using MATLAB ® software (v. 9.1). (Source: Sample information and DeltaR values: Lauren T. Toth (USGS-SPCMSC); Statistical model: Erica Ashe (Rutgers University).)
    Conventional 14C age (years)
    Conventional 14C age (years) from 7500-0 years before present (where present is 1950 C.E.) with a time step of 5 years. (Source: USGS)
    Range of values
    Minimum:0
    Maximum:7500
    Units:conventional radiocarbon years
    Delta-R (14C years)
    Predicted (modeled) ΔR (Delta-R) values (in 14C [radiocarbon] years) for every 5 years conventional radiocarbon years over the range of 0-7500. (Source: USGS)
    Range of values
    Minimum:-324.974494
    Maximum:-119.499169
    Units:14C years
    Delta-R error (1 SE)
    The 1-standard error (1 SE) uncertainty associated with predicted (modeled) ΔR (Delta-R) values (in years) for every 5 years before present over the range of 0-7500 years before present. (Source: USGS)
    Range of values
    Minimum:15.840816
    Maximum:41.750293
    Units:14C years
    Modeled_Nearshore_DeltaR_vs_Conventional_14C_Marine20
    Modeled predictions of ΔR for nearshore locations in south Florida over the range of conventional radiocarbon ages from 9,000 years ago to present with a 5-year time step. All statistical analyses were conducted using MATLAB ® software (v. 9.1). (Source: Sample information and DeltaR values: Lauren T. Toth (USGS-SPCMSC); Statistical model: Erica Ashe (Rutgers University).)
    Conventional 14C age (years)
    Conventional 14C age (years) from 9000-0 years before present (where present is 1950 C.E.) with a time step of 5 years. (Source: USGS)
    Range of values
    Minimum:0
    Maximum:9000
    Units:14C years
    Delta-R (14C years)
    Predicted (modeled) ΔR (Delta-R) values (in 14C [radiocarbon] years) for every 5 years conventional radiocarbon years over the range of 0-9000. (Source: USGS)
    Range of values
    Minimum:-208.627384
    Maximum:-149.872078
    Units:14C years
    Delta-R error (1 SE)
    The 1-standard error (1 SE) uncertainty associated with predicted (modeled) ΔR (Delta-R) values (in years) for every 5 years before present over the range of 0-9000 years before present. (Source: USGS)
    Range of values
    Minimum:17.663302
    Maximum:28.07515
    Units:14C years
    Modeled_Nearshore_DeltaR_vs_230Th_Marine20
    Statistical model output of nearshore ΔR variability from 9,500 years ago to present with a 5-year time step using 230Th age to derive age before present. All statistical analyses were conducted using MATLAB ® software (v. 9.1). (Source: Sample information and DeltaR values: Lauren T. Toth (USGS-SPCMSC); Statistical model: Erica Ashe (Rutgers University).)
    230Th Age (years BP)
    Age before present (modeled from corrected 230Th age before present) from 9500-0 years before present (where present is 1950 C.E.) with a time step of 5 years. (Source: USGS)
    Range of values
    Minimum:0
    Maximum:9500
    Units:years BP
    Delta-R (14C years)
    Predicted (modeled) ΔR (Delta-R) values (in radiocarbon [14C] years) for every 5 years over the range of 9500-0 years. (Source: USGS)
    Range of values
    Minimum:-208.315041
    Maximum:-151.144098
    Units:14C years
    Delta-R error (1 SE)
    The 1-standard error (1 SE) uncertainty associated with predicted (modeled) ΔR (Delta-R) values (in years) for every 5 years over the range of 0-9500 years. (Source: USGS)
    Range of values
    Minimum:18.824325
    Maximum:28.099306
    Units:14C years

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Lauren T. Toth
    • Hai Cheng
    • R. Lawrence Edwards
    • Erica Ashe
    • Julie N. Richey
  2. Who also contributed to the data set?
    Previously collected cores sampled from the USGS Core Archive (https://doi.org/10.5066/F7319TR3) were collected under permits from Dry Tortugas National Park (formerly Fort Jefferson National Monument), Biscayne National Park (formerly Biscayne National Monument), the Florida Keys National Marine Sanctuary (FKNMS), and the Florida State Department of Natural Resources. New cores from the Middle and Upper Keys were collected under permit number FKNMS-2013-097-A1 and FKNMS-2015-058, respectively by Lauren Toth. John "Jack" McGeehin of the USGS Radiocarbon Dating Laboratory provided support for the radiocarbon analysis for this study. This study was supported by a Mendenhall Research Fellowship awarded to Lauren Toth by the United States Geological Survey (USGS) Coastal and Marine Geology Program and the Natural Hazards Mission Area, and by the Climate and Land Use Research and Development Program of the USGS. Erica Ashe's work developing the statistical model was supported by the National Science Foundation (grants ARC-1203415 and OCE-1458904), National Oceanic and Atmospheric Administration grant NA11OAR431010, and the New Jersey Sea Grant Consortium.
  3. To whom should users address questions about the data?
    Lauren T. Toth
    USGS
    600 4th St. S
    St. Petersburg, FL
    USA

    727-502-8029 (voice)
    ltoth@usgs.gov

Why was the data set created?

Radiocarbon and U-series analyses were conducted to quantify the Holocene variability of the local marine radiocarbon reservoir age, ΔR, in south Florida. The reconstructions of ΔR variability from nearshore and open-ocean environments were used to make inferences about millennial-scale changes in oceanography and hydrology and to develop more accurate radiocarbon calibrations for marine samples collected from the region.

How was the data set created?

  1. From what previous works were the data drawn?
    Marine13 (source 1 of 2)
    Reimer, P.J., Bard, E., Bayliss, A., Beck, J.W., Blackwell, P.J., Ramsey, C.B., Buck, C.E., Cheng, H., Edwards, R.L., Friedrich, M., Grootes, P.M., Guilderson, T.P., Haflidason, H., Hajdas, I., Hatté, C., Heaton, T.J., Hoffmann, D.L., Hogg, A.G., Hughen, K.A., Kaiser, K.F., Kromer, B., Manning, S.W., Niu, M., Reimer, R.W., Richards, D.A., Scott, E.A., Southon, J.R., Staff, R.A., Turney, C.S.M., and van der Plicht, J., 2013, IntCal13 and Marine13 radiocarbon age calibration curves 0-50,000 years cal BP: Radiocarbon, University of Arizona, Tucson, Arizona.

    Online Links:

    Type_of_Source_Media: Radiocarbon calibration curve
    Source_Contribution:
    Used to determine the predicted radiocarbon age of samples using their corrected 230Th as calibrated calendar years before present, where present is 1950 (Cal BP).
    Marine20 (source 2 of 2)
    Heaton, T.J., Köhler, P., Butzin, M., Bard, E., Reimer, R.W., Austin, W.E.N., Ramsey, C.B., Grootes, P.M., Hughen, K.A., Kromer, B., Reimer, P.J., Adkins, J., Burke, A., Cook, M.S., Olsen, J., and Skinner, L.C., 2020, Marine20-the marine radiocarbon age calibration curve (0-55,000 cal BP): Radiocarbon, University of Arizona, Tucson, Arizona.

    Online Links:

    Type_of_Source_Media: Radiocarbon calibration curve
    Source_Contribution:
    Used to determine the predicted radiocarbon age of samples using their corrected 230Th as calibrated calendar years before present, where present is 1950 (Cal BP).
  2. How were the data generated, processed, and modified?
    Date: 21-Oct-2015 (process 1 of 5)
    Sample collection: Coral samples were extracted from coral-reef cores previously collected by USGS researchers and housed in the USGS core archive of the St. Petersburg Coastal and Marine Science Center (USGS-SPCMSC; Reich and others, 2012; https://doi.org/10.5066/F7319TR3), one new core collected from Crocker Reef in the Upper Florida Keys, in 2014, and four new cores collected from Sombrero and Tennessee reefs in the Middle Florida Keys, in 2015, as part of the USGS Coral Reef Ecosystems Studies project (https://www.usgs.gov/centers/spcmsc/science/coral-reef-ecosystem-studies-crest?qt-science_center_objects=0#qt-science_center_objects; Toth and others, 2016). Those cores were collected under Florida Keys National Marine Sanctuary (FKNMS) permit numbers FKNMS-2013-097-A1 and FKNMS-2015-058. Data were collected under USGS field activity numbers (FANs) 2014-321-FA, 2015-314-FA, and 2015-325-FA. Additional survey details are available at, https://cmgds.marine.usgs.gov/data_search.php. The geographic locations of those cores were determined using a Garmin GPS and an Ashtec Z-Xtreme DGPS was also used in 2014. The geographic data for the 2014 and 2015 cores were recorded in the North American Datum of 1983 (NAD83). Details listed under the spatial reference information section only apply to the cores collected in 2014–2016. Coral samples were cut from the cores using a tile saw located at the USGS-SPCMSC, which is dedicated to that purpose. The samples were split into two, 1–3-gram subsamples using the tile saw. The subsamples were then sonicated for 15 minutes in a bath of warm, deionized water and dried at 60 degrees Celsius. One subsample of each coral was sent to the USGS Radiocarbon Laboratory (Reston, VA) for radiocarbon analysis and one subsample of each coral was sent to the University of Minnesota, Minneapolis, MN, USA or Xi’an Jiaotong University, Xi'an, China for U-series analysis.
    Date: 07-Dec-2015 (process 2 of 5)
    Dating: All but two coral subsamples were processed at the USGS Radiocarbon Laboratory in Reston, VA and were radiocarbon dated using accelerator mass spectrometry (AMS) at the Center for AMS, which is located on the UC Berkley campus within the Lawrence Livermore National Laboratory using standard techniques. The δ13C of those samples was either measured by the University of California, Davis Stable Isotope Laboratory or, if not measured, were assumed to be 0±3‰. Measured 14C ages were corrected for fractionation of 13C using the d13ccorr spreadsheet available at http://calib.org/calib/instruct.html. The other two samples were dated previously (Lidz and others, 2003; C. Reich, unpublished data) using bulk, radiometric radiocarbon dating at Beta Analytic, Inc. or Geochron Laboratories. U-series ages were determined by H. Cheng and R.L. Edwards at the University of Minnesota and Xi’an Jiaotong University using multi-collector inductively coupled plasma mass spectrometry according to the procedures described in Cheng and others (2013). Measured 230Th ages were corrected using an initial 230Th/232Th atomic ratio of 4.4 x 10^-6 with an uncertainty of 50% (±2.2 standard error). Those are the values for a material at secular equilibrium, with the bulk Earth 232Th/238U value of 3.8.
    Date: 07-Dec-2015 (process 3 of 5)
    ΔR was calculated as: ΔR = 14C (conventional) – 14C (expected from Marine13 in the original dataset or Marine 20 in the updated dataset) where 14C (conventional) is the conventional radiocarbon age of the sample and 14C (expected from Marine13 or Marine 20) is the predicted 14C age from the marine calibration curve using the corrected 230Th age before present as Cal BP. The error terms for ΔR were calculated by combining the two standard error uncertainties associated with the conventional 14C age (SE1) and expected 14C age from the appropriate calibration curve (SE2): SDcombined = square root (SE1^2 + SD2^2)
    Date: 16-May-2016 (process 4 of 5)
    Statistical modeling: Researchers combined the coral-based snapshots of ΔR using an empirical hierarchical model with Gaussian process priors to 1) reconstruct temporal variability in ΔR during the Holocene (ΔR versus 230Th ages) and 2) predict values of ΔR and ΔR uncertainty for use in calibrations of radiocarbon ages from the region (ΔR versus conventional 14C ages) for both the open-ocean and nearshore sites. The model outputs are found in the files: Modeled_OpenOcean_DeltaR_vs_230Th, Modeled_Nearshore_DeltaR_vs_230Th, Modeled_OpenOcean_DeltaR_vs_Conventional_14C, and Modeled_Nearshore_DeltaR_vs_Conventional_14C. Data that were not included in the model are indicated in the "Data included in statistical models? (Y/N)" attribute in FKRT_Coral_Based_DeltaR and DeltaR_Data_Screening_Summary, for the reasons described in DeltaR_Data_Screening_Summary. All statistical analyses were conducted in MATLAB ® version R2019a Update 6 (9.6.0.1214997).
    Researchers used a Gaussian process prior distribution with prior mean equal to the average ΔR for each model through time. This prior distribution consists of 1) a time-dependent non-linear term defined with a Matérn correlation function with a smoothness parameter 3/2 and 2) a white noise term to capture high-frequency variability in ΔR that is not captured by the non-linear term. The hyperparameters of the model include the amplitude (or prior standard deviation), the characteristic time scale of variability, and the prior standard deviation of the white noise. These parameters are optimized through maximum-likelihood estimation based on the coral-based estimates of ΔR and the 230Th ages of those samples.
    For the previous, Marine13 model, these parameters are as follows: -Open ocean: Non-linear standard deviation=38, Temporal scale=850, White noise standard deviation=1 -Nearshore: Non-linear standard deviation=38, Temporal scale=850, White noise standard deviation=20
    For the updated, Marine20 model, these parameters are as follows: -Open ocean: Non-linear standard deviation=64.1, Temporal scale=1264.4, White noise standard deviation=0.9 -Nearshore: Non-linear standard deviation=28.1, Temporal scale=254.2, White noise standard deviation=32.5
    For more information on the criteria for excluding data and details of the statistical model see Toth and others (2017).
    Date: 21-Feb-2017 (process 5 of 5)
    Data Screening: All corals included in this study were carefully examined prior to dating and were generally found to be in excellent condition. Sixteen of the samples included in this study were also previously screened for diagenesis by X-ray diffraction (XRD) using a Bruker D4 X-ray diffractometer. These analyses indicated that all samples contained <5% calcite and, in most cases, the samples were nearly 100% aragonite. Researchers screened an additional subsample (N=14) of corals using the S-3500N Hitachi scanning electron microscope (SEM) housed at the University of South Florida’s College of Marine Science. Researchers evaluated the corals for evidence of: secondary calcite precipitation, secondary aragonite needles, and/or dissolution. SEM imaging of the samples generally showed only the localized presence of secondary aragonite and suggested that diagenetic alteration was negligible overall; however, researchers did find evidence of significant diagenesis in three samples: LK-MG-2-0, MK-AR-2-0, and BP-FR-2-55. Researchers also screened the U-series data based on three criteria: 1) δ234U within 10 per mil of modern seawater (147 per mil), 2) 232Th less than 2 parts per billion (ppb), and 3) 238U within taxon-specific ranges for modern or Holocene corals (~2800–3800 ppb for Acropora spp. and ~2000–3200 for the massive coral taxa Orbicella spp., Diploria spp., Montastraea cavernosa, and Colpophyllia natans). Samples that did not meet the U-series or diagenetic criteria were excluded from statistical analysis. Descriptions of the screening procedures and reasons for exclusion are provided in: DeltaR_Data_Screening_Summary.zip
  3. What similar or related data should the user be aware of?
    Toth, L.T., Stathakopoulos, A., and Kuffner, I.B., 20160721, The structure and composition of Holocene coral reefs in the Middle Florida Keys: U.S. Geological Survey Open-File Report 2016-1074, U.S. Geological Survey, Reston, VA.

    Online Links:

    Reich, C., Streubert, M., Dwyer, B., Godbout, M., Muslic, A., and Umberger, D., 20120104, St. Petersburg Coastal and Marine Science Center's Core Archive Portal: U.S. Geological Survey Data Series 626, U.S. Geological Survey, Reston, VA.

    Online Links:

    Toth, L.T., Cheng, H., Edwards, R.L., Ashe, E., and Richey, J.N., 2017, Millennial-scale variability in the local radiocarbon reservoir age of south Florida during the Holocene: Quaternary Geochronology Volume 42, Elsevier, Amsterdam, Netherlands.

    Online Links:

    Cheng H., Edwards, R.L., Shen, C.-C., Polyak, V.J., Asmerom, Y., Woodhead, J., Hellstrom, J., Wang, Y., Kong, X., Spötl, C., Wang, X., and Alexander, E.C., 20130523, Improvements in 230Th dating, 230Th and 234U half-life values, and U–Th isotopic measurements by multi-collector inductively coupled plasma mass spectrometry: Earth and Planetary Science Letters Volumes 371–372, Elsevier, Amsterdam, Netherlands.

    Online Links:

    Lidz, B.H., Reich, C.D., and Shinn, E.A., 20030701, Regional Quaternary submarine geomorphology in the Florida Keys: GSA Bulletin Volume 115, Geological Society of America Bulletin, Boulder, CO.

    Online Links:

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

  1. How well have the observations been checked?
    All values in tables were cross-checked for accuracy against original versions of the tables and model/instrument outputs.
  2. How accurate are the geographic locations?
    No formal positional accuracy tests were conducted.
  3. How accurate are the heights or depths?
    No formal positional accuracy tests were conducted.
  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 rest of the metadata record carefully for additional details.
  5. How consistent are the relationships among the observations, including topology?
    The data were screened by the authors for accuracy and all data falls within acceptable/logical ranges.

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:
Public domain data from the U.S. Government are freely redistributable with proper metadata and source attribution. The U.S. Geological Survey requests to be acknowledged as originator of these data in future products or derivative research.
  1. Who distributes the data set? (Distributor 1 of 1)
    Lauren T. Toth
    USGS
    600 4th St. S
    St. Petersburg, FL
    USA

    727-502-8029 (voice)
    ltoth@usgs.gov
  2. What's the catalog number I need to order this data set?
  3. What legal disclaimers am I supposed to read?
    Although these data have been processed successfully on a computer system at 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. The USGS shall not be held liable for improper or incorrect use of the data described or contained herein. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
  4. How can I download or order the data?

Who wrote the metadata?

Dates:
Last modified: 30-Aug-2021
Metadata author:
Lauren T. Toth
USGS
Research Physical Scientist
600 4th St. S
St. Petersburg, FL
USA

727-502-8029 (voice)
ltoth@usgs.gov
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)
This page is <https://cmgds.marine.usgs.gov/catalog/spcmsc/FL_keys_radiocarbon_reservoir_age_variability_metadata_Marine20.faq.html>
Generated by mp version 2.9.50 on Tue Sep 21 18:18:49 2021