DOI: 10.5061/dryad.7h44j103k
title: Supplemental Materials: Early Miocene land mammals and chronology of the Belgrade Formation, eastern North Carolina

description: Early Miocene land mammals from eastern North America are exceedingly
 rare. Over the past several decades, a small but significant vertebrate
 fauna has been recovered by paleontologists and citizen scientists from
 the Belgrade Formation at the Martin Marietta Belgrade Quarry in eastern
 North Carolina. This assemblage has 12 land mammal taxa, including beaver
 (Castoridae), stem lagomorph, carnivorans (Mustelidae, Ailuridae), horses
 (Equidae), rhinoceros (Rhinocerotidae), tapir (Tapiridae), peccary
 (Tayassuidae), anthracothere (Anthracotheriidae), entelodont
 (Entelodontidae), and protoceratid (Protoceratidae). Taken together, the
 biochronology of this Maysville Local Fauna indicates a late Arikareean
 (Ar3/Ar4) to early Hemingfordian (He1) North American Land Mammal Age
 (NALMA). This interval, which includes the Runningwater Chronofauna,
 documents numerous important Holarctic immigrants, including Amphictis,
 Craterogale, and cf. Menoceras found at this locality. Strontium isotope
 stratigraphy (SIS) of shark teeth collected in situ from the Belgrade
 Formation yields an age of 21.4 + 0.13 Ma, which validates the age of
 interbedded land mammals within this unit. It is also consistent with the
 late Arikareean (Ar3/Ar4) biochronology and Aquitanian Neogene marine
 stage. New SIS analyses of oysters (Striostrea gigantissima) and clams
 (Chione) from this mine, previously assigned to late Oligocene or late
 Miocene, are significantly older (28.0 + 0.22 Ma and 27.6 + 0.26 Ma,
 respectively) than the land mammals. Depending upon stratigraphic
 interpretations, these may confirm an older marine facies within the
 Belgrade Formation. This locality is thus important because of its marine
 and terrestrial tie-ins that facilitate intercalibration of both NALMAs
 and Cenozoic marine stages.
description: This dataset contains the individual analyses for the
 strontium-ratio age determinations using treated sample powders taken from
 Oligocene oysters and Miocene shark teeth collected from the Martin
 Marietta Belgrade Quarry in eastern North Carolina. It also includes the
 statistical tests and relevant R code that were used for the
 statistics.
description: # Supplemental Materials: Early Miocene land mammals and chronology of the
 Belgrade Formation, eastern North Carolina
 [https://doi.org/10.5061/dryad.7h44j103k](https://doi.org/10.5061/dryad.7h44j103k) ## Description of the data and file structure These files contain the original data and analyses used for the interpretation of the strontium-ratio age determinations of Oligocene oysters and Miocene land mammals collected from the Martin Marietta Mine in Eastern North Carolina. These interpretations were based on previous references (cited in the main article) that developed a Neogene age curve based on unique variations in strontium ratios in the oceans at different times in the geological past. This folder contains three files pertaining to the above-referenced paper: 1\. Belgrade_Supplementary_Materials_Updated_10.10.2025.pdf  Statistical analyses used for the interpretation of the strontium-ratio age determinations. 2\. Belgrade_R_Script.R R code used for the statistical analyses presented in file 1 above. 3\. Belgrade_Raw_Sr_Data_Final_10.12.2025.csv Raw data Sr-isotope data produced on the mass spectrometer used for the statistical analyses presented in file 1 above. Information about the analytical laboratory where these analyses were conducted can be found at: [https://geology.ufl.edu/research-and-facilities/facilities/inductively-coupled-plasma-mass-spectrometry-facility-icp/](https://geology.ufl.edu/research-and-facilities/facilities/inductively-coupled-plasma-mass-spectrometry-facility-icp/) These interpretations were based on previous references (cited in the main article) that developed a Neogene age curve based on unique variations in strontium ratios in the oceans at different times in the geological past. **Abbreviations** 87/86, 86/88, 84/86, 84/86 are Sr (strontium) isotope ratios corr, corrected for interference (87/86 Rb corr) ANOVA, Analysis of Variance statistical test Diff, difference Exp., experimental HSD, Honestly Significant Difference, Tukey statistical test ID, internal laboratory sample identifier Ma, megaannum, or millions of years ago on the geological time scale. Max, Maximum Min, minimum NA, not applicable NBS; National Bureau of Standards *P* or *p*, probability R; statistical computing software package Rb; rubidium SE, standard error (sigma) σ error, standard deviation Sr, strontium (V), voltage ## Code/software Anything that can open CSV files, R scripts, and PDFs. The R code and scripts were developed here for the statistical analyses. ## Access information Other publicly accessible locations of the data: * Not applicable Data was derived from the following sources: * As indicated above, based on independent laboratory analyses conducted during this study.