Dataset of oxygen, carbon, and strontium isotope values from the Imperial Roman site of Velia (ca. 1st-2nd c. CE), Italy

The oxygen (δ18Ocarbonate), strontium (87Sr/86Sr), and previously unpublished carbon (δ13Ccarbonate) isotope data presented herein from the Imperial Roman site of Velia (ca. 1st to 2nd c. CE) were obtained from the dental enamel of human permanent second molars (M2). In total, the permanent M2s of 20 individuals (10 male and 10 female) were sampled at the Museo delle Civiltà in Rome (formerly the Museo Nazionale Preistorico Etnografico “L. Pigorini”) and were subsequently processed and analysed at McMaster University. A subsample of teeth (n=5) was initially subjected to Fourier transform infrared spectroscopy (FTIR) analysis to assess for diagenetic alteration through calculation of crystallinity index (CI) values. Subsequently, tooth enamel was analysed for δ13Ccarbonate and δ18Ocarbonate (VPDB) using a VG OPTIMA Isocarb isotope ratio mass spectrometer (IRMS) at McMaster Research for Stable Isotopologues (MRSI), and 87Sr/86Sr was measured by dynamic multi-collection using a thermal ionization mass spectrometer (TIMS) in the School of Geography and Earth Sciences. The dental enamel isotope data presented represent the first δ18O, δ13Ccarbonate, and 87Sr/86Sr values analysed from Imperial Roman Campania to date, providing data of use for comparative analyses of δ18O, δ13C, and 87Sr/86Sr values within the region and for assisting in documenting human mobility in archaeological contexts. Full interpretation of the δ18O and 87Sr/86Sr data presented here is provided in “Imperial Roman mobility and migration at Velia (1st to 2nd c. CE) in southern Italy” [1].

Isocarb isotope ratio mass spectrometer (IRMS) at McMaster Research for Stable Isotopologues (MRSI), and 87 Sr/ 86 Sr was measured by dynamic multi-collection using a thermal ionization mass spectrometer (TIMS) in the School of Geography and Earth Sciences. The dental enamel isotope data presented represent the first δ 18 O, δ 13 C carbonate , and 87 Sr/ 86 Sr values analysed from Imperial Roman Campania to date, providing data of use for comparative analyses of δ 18 O, δ 13 Table   Subject Archaeology Specific subject area Isotope analyses Type of data Table  Figure Graph How data were acquired Fourier transform infrared spectroscopy (FTIR); VG OPTIMA Isocarb isotope ratio mass spectrometer (IRMS); thermal ionization mass spectrometer (TIMS) Data format Raw Analysed Parameters for data collection Permanent second molars (M2) were selected (n = 20) from an equal number of male (n = 10) and female (n = 10) individuals, providing a sex balanced sample. Permanent second molars were chosen as a control for age, based on crown development of the permanent second molar being complete by ca. 7 to 8 years of age. Description of data collection Utilizing Fourier transform infrared spectroscopy (FTIR), crystallinity index (CI) values for a subsample of individuals (n = 5) were calculated to assess apatite preservation at Velia [4] . Ground enamel samples were then prepared for δ 13

Value of the Data
• These data reflect the first 87 Sr/ 86 Sr, δ 13 C carbonate , and δ 18 O carbonate values derived from Imperial Roman bioarchaeological contexts at Velia and more broadly Campania, Italy. • These data will be useful to bioarchaeological researchers investigating questions of diet, mobility, and migration, particularly for the Imperial Roman era and for contexts in southwestern Italy.
• These data can be utilized for comparisons to 87 Sr/ 86 Sr, δ 13 C carbonate , and δ 18 O carbonate values from other sites as well as for future research at and around Velia. The data presented may be utilized for subsequent studies of the same individuals through integration into skeletal biological, palaeodemographic, palaeogenetic, palaeopathological and/or additional isotopic analyses (e.g. S, Pb).

Data Description
The data comprise crystallinity index (CI) values of five individuals from Velia, strontium ( 87 Sr/ 86 Sr), carbon carbonate ( δ 13 C carbonate VPDB), and oxygen carbonate ( δ 18 O carbonate VPDB) values using delta notation ( δ) in per mil increments ( ‰ ). The presented values were derived from the permanent second molars (M2) of twenty individuals (10 male and 10 female) dated to Imperial Roman (ca. 1 st to 2 nd c. CE) contexts at the site of Velia located in the Cilento of Lucania, modern day Campania, Italy. Table 1 presents dental enamel crystallinity index (CI) values for five randomly selected individuals (two males and three females). Given the uniform environmental contexts of deposition at Velia, the five sampled individuals were utilized as a gauge of apatite preservation for the broader site environs.   [2] considered in conjunction with the local range for dental values at Portus [3] , which falls within the same isopleth as Velia.
To consider the variation between the expected local bioavailable baseline for 87 Sr/ 86 Sr at Velia, as derived from nine pig teeth, a boxplot presenting the expected local 87 Sr/ 86 Sr baseline, male (n = 10 individuals), and female (n = 10 individuals) 87 Sr/ 86 Sr values is presented in Fig. 2 .
Similarly, a boxplot comparing the δ 18 O carbonate VPDB of male (n = 10) and female (n = 10) individuals analysed from Velia is presented in Fig. 3 .

Sampling approach
The rationale for collecting the data presented herein was to compare 87 Sr/ 86 Sr and δ 18 O c values preserved in human dental enamel to expected local 87 Sr/ 86 Sr and δ 18 O dw values for the region around Velia, to assess for possible instances of mobility to this Imperial Roman (ca. 1st to 2nd c. CE) secondary port settlement located in the Cilento of Lucania. Permanent second molars (M2) from twenty adult individuals interred at Velia were collected in 2012 and 2013 from the Museo delle Civiltà (formerly the Museo Nazionale Preistorico Etnografico "L. Pigorini") in Rome, Italy where the human skeletal remains from Velia are curated. All sampled individuals were recovered from inhumation burials. A sex balanced sample of 10 males and 10 females was chosen to provide equal representation for comparison of isotope values. Following collection in Rome, all M2 samples were prepared for isotopic analyses at McMaster University, in Hamilton, Ontario, Canada.

Dental enamel sample pre-treatment
All of the human second molars (M2) subjected to isotopic analyses were initially manually brushed to remove any adhering debris before being submersed in distilled water (dH 2 O) and ultrasonicated for a period of 10 min. Ultrasonication was repeated three times changing the water for each rinse, after which the teeth were dried in a drying oven at 60 °C before being drilled to remove enamel for sampling.

FTIR and CI analyses
Testing for diagenetic alteration of apatite quality for the Velia samples was completed through subsampling of five randomly selected individuals (Velia 134, 146, 194  infrared spectroscopy (FTIR). FTIR spectra were utilized to calculate crystallinity (CI) index according to CI = (A 565 + A 605 )/A 595 , where A x is the absorbance at wave number x, assuming a straight line baseline between 750 and 450 cm −1 [4] . Samples for FTIR analysis were first cleaned before the enamel was ground into a fine powder and passed through a #200 mesh sieve. Each ground enamel sample was combined with dry potassium bromide (KBr) and ground before being compressed into pellets at 10,0 0 0 psi. The compressed pellets were then analysed using a Nicolet 6700 dry nitrogen purged FTIR, room temperature DTGS detector with extended KBr beam splitter, resolution 4 cm −1 (wavenumber) at 32 scans. CI values for all five individuals were ≤3.8, indicating sufficient apatite preservation and absence of diagenetic alteration ( Table 1 ).

Sample preparation for δ 13 C and δ 18 O VPDB analysis
From each molar sampled, ≥10 mg of powdered dental enamel was removed using a diamond tipped drill bit in a hand-held electric Dremel drill. After each use the drill bit was soaked in 0.25M hydrochloric acid (HCl) for ca. 10 min to avoid cross contamination and then rinsed in distilled water (dH 2 O). After weighing, enamel powder was collected in 1.5 ml plastic centrifuge microtubes.
Powdered enamel samples were treated with 0.04 ml of 2.5% bleach solution (NaClO) per mg of sample after which they were agitated and allowed to react for a period of up to 24 h. Following this reaction, samples were centrifuged and rinsed with de-ionized water five times, centrifuging after each rinse. Each sample next had 0.04 ml of 1M acetic acid acetate buffer (CH 3 COOH) per mg of sample added to remove potential diagenetic secondary carbonates. Samples were agitated and allowed to react for a period of up to 24 h. Samples were then centrifuged and rinsed five times with de-ionized water, centrifuging after each rinse. After the fifth rinse samples were centrifuged and the remaining water removed before the teeth were dried in a drying oven at 60 °C [5] .
Once the samples were dry, 2 mg of enamel powder was weighed into stainless steel cups. Each sample was reacted with 100% phosphoric acid at 90 °C in an autocarb analyser to produce CO 2 gas, which was analysed on a VG OPTIMA Isocarb isotope ratio mass spectrometer (IRMS) at the McMaster Research for Stable Isotopologues (MRSI) laboratory to measure δ 18 O and δ 13 C values. For each carousel containing 14 samples one sample was run in duplicate to test for accuracy and reproducibility, which is to say 13 samples and 1 duplicate were run with each carousel. Returned δ 18 O and δ 13 C values are presented using delta notation ( δ) defined as, where, x = sample and std = standard, presented in per mil ( ‰ ) increments in refer-

Sample preparation for 87 Sr/ 86 Sr
From each molar sampled, ≥60 mg of powdered dental enamel was removed using a diamond tipped drill bit in a hand-held electric Dremel drill. After each use the drill bit was soaked in 0.25M HCl for ca. 10 min to avoid cross contamination and then rinsed in distilled water (dH 2 O). After weighing, enamel powder was collected in 1.5 ml plastic centrifuge microtubes.
Strontium extraction followed the protocol of the thermal ionization mass spectrometry (TIMS) laboratory directed by Dr. Alan Dickin in the School of Geography and Earth Sciences at McMaster University. Enamel was initially dissolved in 1.2 ml of 2.5 M HCl. Following full dissolution of the enamel, samples were centrifuged for 10 min. Cation exchange was employed to complete the strontium separation. Cation exchange columns were calibrated by employing a test "spiked" sample allowing for the stage of Sr collection to be assessed. In order to cleanse the cation exchange columns before use, 10 ml of deionized water was introduced after which a wash of 60 ml of 6 M HCl was introduced, followed by 10 ml of deionized water, and then finally 5 ml of 2.5 M HCl.
Dissolved enamel solution for each individual was introduced to the exchange columns in 1 ml portions and was washed into the column using 1 ml of 2.5 ml HCl, after which a wash of 3 ml of 2.5 M HCl was introduced. Waste sample matrix was eluted using 20 ml of 2.5 M HCl. After the 20 ml elution, 6 ml of 2.5 M HCl was introduced to the columns to collect the strontium. Strontium was collected in 4 ml intervals into Teflon beakers. Once the strontium phase was collected samples were placed under a heat lamp to dry to a solid state. Once dry, each sample was loaded onto a pre-treated single tantalum filament in dilute phosphoric acid, after which the samples were loaded in sequence into a vacuum system [6] . 87 Sr/ 86 Sr values of all samples were determined by dynamic multi-collection using a thermal ionization mass spectrometer (TIMS) in the School of Geography and Earth Sciences at McMaster University. Resultant strontium values were fractionation normalized to 88 Sr/ 86 Sr = .1194, with an average 87 Sr/ 86 Sr = 0.71026 ±18 (1 σ ) for the NIST 987 Sr standard and internal precision (within-run precision) of ±0.0 012-0.0 018% (1 σ ) standard error based on 150 dynamic cycles.

Data Analysis
Of the 20 samples analysed for 87 Sr/ 86 Sr and δ 18 O, 5/20 (25%) fall outside of the expected local δ 18 O dw range: Velia 57, 134, 194, 205, and 211; none of the individuals sampled fall outside of the expected local bioavailable 87 Sr/ 86 Sr range ( Fig. 1 ). Of the five individuals outside of the expected local δ 18 O dw range, 2/5 (40%) are female (Velia 134 and 205) and 3/5 (60%) are male (Velia 57, 194, and 211). In terms of δ 18 O c (VPDB) values, the interquartile range for both the male and female individuals sampled are overall similar, with males having a slightly less negative median value than females ( Fig. 3 ). The same is not true of 87 Sr/ 86 Sr values, where a much narrower interquartile range of values is evident for the female individuals sampled than the males ( Fig. 2 ). The interquartile ranges for both male and female 87 Sr/ 86 Sr values, however, fall within the interquartile range for the expected local bioavailable 87 Sr/ 86 Sr baseline for the area around Velia as established from pig dental enamel [1 , 14] . The δ 13 C values of the 20 individuals analysed fall within a relatively narrow range, spanning from −13.6 ‰ (Velia 205) to −11.5 ‰ (Velia 160). Considering these δ 13