Radiometric ages and descriptive data for Holocene corals from southeast Florida

Sampling of Holocene corals: This database includes data from samples collected in previous studies as well as new coral samples from Holocene reefs in southeast Florida collected by USGS researchers and collaborators as part of this study. Some samples were collected from rotary core records (Lidz and others 2003; Banks et al. 2007; Stathakopoulos and Riegl 2015) and those samples can be identified by the "Core ID" attribute. Some other samples were collected from existing man-made exposures of the reef framework from dredging (Port Miami samples, this study; Shinn and others 1977), a pipeline installation (Lighty and others 1978), or a ship grounding (Precht and others 2000). The remaining samples were collected from the reef surface using either a hammer and chisel or an underwater drill equipped with a coring bit. Detailed methods related to sample collection and processing are provided in Toth and others (2021). All samples collected as part of this study are stored in the USGS Core Archive (https://doi.org/10.5066/F7319TR3).

Sample elevation: The water depths where the samples were collected were recorded in the field using underwater depth gauges. For more recent sample collections, the field-based measurements were corrected to mean sea level using data from the nearest NOAA tidal datum. Sample elevations that could not be tide corrected, were assumed to be relative to mean sea level, but an error term equivalent to one-half the tidal depth range at the nearest National Oceanic and Atmospheric Administration (NOAA) tidal datum was applied. We also incorporated elevation errors associated with 1) estimating water depths with underwater depth gauges (0.5 meters [m]), 2) the rotary coring method (0.15 m), and 3) other "sampling depth" uncertainties. For samples collected from rotary cores, the sampling depth uncertainty is the uncertainty associated with determining the location of a sample in a core. This is primarily a consequence of the poor recovery of rotary cores, which allows material to shift within intervals. This uncertainty is scaled based on where the sample was collected within the interval. For samples collected within 0.5 foot (0.1524 m) of the top of the interval, this uncertainty is 0.5 feet (0.1524 m). For samples collected within 1 foot of the top or bottom of an interval, this uncertainty is 1 foot (~0.3 m). For all other samples, the uncertainty is 1/2 the length of the interval. Other sources of sampling depth uncertainty include: a depth range rather than a specific depth for some samples (BR-IR-MR-8.5b,c,d); the full range of depths was applied as an uncertainty and uncertainty associated with whether in place or collapsed Acropora palmata framework was sampled (MD-IR-PM and MD-OR-PM surface samples).

Radiometric dating: Radiometric ages of the samples were measured by a combination of radiocarbon and U-series dating. Radiocarbon ages for the majority of the samples were determined by accelerator mass spectrometry (AMS) at either the Woods Hole Oceanographic Institution (WHOI) National Ocean Sciences Accelerator Mass Spectrometry (NOSAMS) facility, at the Lawrence Livermore National Laboratory, or the Center for Applied Isotope Studies at the University of Georgia. Some of the samples included in this study were radiocarbon dated using the rapid methodology developed at the University of California, Irvine (Bush and others 2013). Some samples dated in previous studies were radiocarbon dated using standard, bulk dating methodologies (Shinn and others 1977; Lighty and others 1978; Precht and others 2000; Lidz and others 2003), and some samples from Stathakopoulos and Riegl (2015) and Banks and others (2007) were dated using U-series methodologies. Ages from previous studies reported as conventional radiocarbon ages were corrected for the fractionation of δ13C based on measured δ13C or δ13C=0±4‰, if not measured. All radiocarbon ages were calibrated to years before present (where “present” is 1950) using the temporally-explicit local radiocarbon reservoir age offsets for the nearshore regions of south Florida derived by Toth and others (2017).