Multi-isotope analysis

Durham Research Online Deposited in DRO: 02 June 2009 Version of attached le: Published Version Peer-review status of attached le: Peer-reviewed Citation for published item: Jay, M. and Grimes, V. and Montgomery, J. and Lakin, K. and Evans, J. (2007) 'Multi-isotope analysis.', in The archaeology of the A1(M) Darrington to Dishforth DBFO road scheme. Lancaster: Oxford Archaeology North, pp. 351-354. Further information on publisher's website: http://thehumanjourney.net//index.php?option=comc ontenttask = viewid = 137Itemid = 40 Publisher's copyright statement: Additional information: Use policy The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that: • a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders. Please consult the full DRO policy for further details. Durham University Library, Stockton Road, Durham DH1 3LY, United Kingdom Tel : +44 (0)191 334 3042 | Fax : +44 (0)191 334 2971 http://dro.dur.ac.uk • theconsumptionofmarineand freshwaterdietary resources. Collagen extraction was undertaken using the procedure outlined in Richards and Hedges (1999). This was modified by the use of ultrafilters (Brown et al 1988), which are used to remove degraded and contaminating molecules under 30 kD. All data presented. here have CN ratios within the range 2.93.6, which indicates an extraction within acceptable quality limits (DeNim 1985). All collagen yields are at, or above, 1.8%, meaning that they are all within the yield limits considered indicative of good-quality collagen when ultrafilters are not used (Ambrose 1990). The use of these filters reduces yields, since degraded molecules are removed, so that the yields are considered. well within the acceptable range. Multi-Isotope Analysis .253 Introduction Tooth enamel and bone samples from six cattle from the ditch around chariot burial 2230 (Site 0 (Ferry Fryston», and of 15human burials from Sites 0 (Ferry Fryston). Q M, and XX15. were submitted for isotope analysis. Thework wascanied oulas partofanongoing Iron Age Isotope Research Project at the University of Bradford, funded by the AHRB, NERC, the University of Bradford, and the Highways Agency. .2023 .2263 Analylical precision (' 0) - - - - - - - - - - - - - - - - ' e. Bonesamples forcarbon and nitrogen isotope analysis, and enamel samples for oxygen isotope analysis. were prepared and analysed at the University of Bradford. Strontium isotope data were obtained from tooth enamel samples, which "",ere prepared at the University of Bradford following the method given in Montgomery (2002), and then transferred to the clean laboratory suite at the NERC Isotope Geosciences Laboratory, Keyworth, NOttinghamshire, for chemical separation and analysis. The strontium data for the cattle were obtained as part of an MSc dissertation project at the University of Bradford (Lakin 20(4). -21.8 -21.6 -21.<1 -21.2 -21.0 .zoe -2J.6 -204 -312 ·:;no 1\"Cr-l FiguI'C 184: Carbo" and llitTogr:.'11 isotopic data for tile If/wums The 16 human burials dated from the Bronze Age through to the Romano-British period and included the Iron Age chariot burial (Fig 184). The analysis was undertaken on rib samples in the majority (13), with some long bone cortex. Collagen signals reAect average diet over a number of years, as the bone content turns overin the individual, so that the values obtained are for long-term consumption patterns over a lifetime, rather than the short·term childhood signals from tooth enamel seen in the strontium and oxygen analyses. Carbon and nitrogen isotope analysis Mandy Jay 1llecarbonand nitrogen isotopic values fromhumanand animal bone collagen reflect the diet, partirularly thatof dietary protein (Ambrose 1993;Sealy 2001). Using such data, it is often possible to draw conclusions about • the levels of animal protein (meat and dairy products) in the diet as compared toterrestrial plant consumption, ie the identification of omnivorous and carnivorous diets; • the consumption of plants following the C~ photosynthetic pathway (or protein from animals consuming such plants themselves), as compared to the consumption of C3 plants; In order to interpret these data fully, a 'baseline' from local, contemporaneous fauna (particularly herbivores) would normally be required as an indicator of the environmental background. The faunal data available for comparison in this case are from the cattle deposited in the enclosure ditch of the chariot burial, which date to a period some time after that burial. and from unpublished lronAgedata from another study in the area (Booth 2003). Six of the cattle were analysed, and these provided averages of the ratios of llC_I3(: (5IJCof-21.9±0.3700) and of l~N_15N (oISN of5.9± 1.2'100) 351 compared well with the unpublished faunal data from Booth. Nitrogen values can fluctuate across the UK, depending on local environment (Jay, unpublished Iron Age data). In addition, the possibility that the cattle may have been imported to the area must be borne in mind when using them as a baseline. -2 -5 -0 Given the faunal data available, the vaJues obtained from the majority of the humans would indicate around one trophic level, with a difference between the average Bnc for the cattle and Middle Iron Age humans of 1.4'%10 and B'5N of 3.6700. This indicates an omnivorous diet, with no indication of a C 4 plant input (as would be expected for the UK), or of the consumption of marine foods. Both the human and faunal data are fully consistent with a diet obtained in the UK. The two Bronze Age individuals have values which are noticeably more negative on the carbon scale, and it is possible that this was an environmentally driven differentiation, but no fauna are available for comparison. -11 -" -17 -20 ""' Figurc 185: Represelltatioll of tile ll'eighlt.>d flIl1IlIal m:ygell isotope sigllal ill precipitatioll for Europe ordertodeterminewhethertheyspenttheirchildhood in or near the region in which they were buried. Enamel sections representing the entire tooth crown were removed from permanent molar and premolar teeth and mechanically separated from dentine. They were powdered in a stainless steel mortar and pestle before being treated with 2.5% sodium hypochlorite to remove possible organic contaminants. Phosphate was then extracted as silver phosphate according to the method described in Dettman ct a/ (2001). Burial 253 from Site XX15 also has a noticeably different signal in terms of both carbon and nitrogen. Radiocarbon assay has placed this individual, represented by a disarticulated skeleton, in the Late Iron Age (see 0/3, p 75). The differences might represent an unusual pattern of consumption, but the differentiation could also result from dHfering environments, either over time or across space (if this was a mobile individual). If not an incomer to the site, it is possible that the data suggest freshwater fish were a major contribution to the individual's diet. Results from the oxygen isotope analysis were plotted, together with the strontium isotope ratios (Fig 186). Although conclusions from the oxygen isotope data remain tentative, several observations can be made. Oxygen isotope analysis VauglwlI Grimes tJ. Chariot burial oMiddle Iron Age x Iron AgelRoman o Beaker + Early Bronze Age 0.717 The oxygen isotope ratio of mammalian bone and tooth enamel phosphate (BI8() ) is related to oxygen isotopes in precipitation «()Ill() :>ci ) through drinking water, and the BI8() rOO signaf is :trongly influenced by envi ronmental a~d geographic parameters such as air temperature, latitude, distance from the coast, and altitude(Dansgaard 1964),Assuch, the5 l f() -B'8() . relationship has been Widely used by r~searc~';;~ as a tool to reconstruct past climates (Genoni el aJ 1998; Longinelli 1984; Luz and Kolodny 1985) and, increasingly, to detect human and animal migration (Whiteetal2004). By analysing theBI8() value in tooth enamel, which incorporates an enviroh.mental signal during early life, and comparing it to the 5"10 n.>ci value in local rainfall, it may be possible to deterrhin~ whether or not an individual has moved, during their lifetime, between geographical regions that have different Bll1()pre<:ip signatures (Fig 185). 00 I:> 0 00 0.71S . 0.713 825 \ >: >: ,l'O.711 >: Modem 0'"0_ range + 0 0.709~ o , L-,-""";.='ytlao:.:,c~I~'~-,'-~_~_~ 0.707.., ·13 ·12 -11 -10 -9 ~__~ -5 ·3 ·2 Figure 186: Oxygen alld strontium isolopc ratios ilt lootll ellamel With the possible exception of individual 825 (Site Q), the range in oxygen isotope values is relatively restricted, around a mean value of -7.8700 ± 0.7 (10). When coupled with the analytical error, In the presentstud y, phosphateoxygen isotope analysis was carried outon tooth enamel from 12 individuals, in 352 obtained from rainwater and plants grown on the local Magnesian Limestone (McArthuret a12001; Fig 187). This suggests that the cattle were not raised together in the same herd, and were not grazed on limestone pasture during the first year of life, which is when the teeth analysed in this study (second mandibular molars) would have mineralized (Brown et a11960). Therefore, the isotope data suggest that either the cattle came from disparate and varied locations, before or after slaughter, or, perhaps less probably, that the bulk of their diet consisted of imported food. these values a.re consistent with modern annual 6l!Qpn,-opfor a region between 10° E latitude and 100 W latitude, or most of current Western Europe (Fig 185). Therefore, it is likely that 11 of the 12 individuals sampled for oxygen isotope analysis spent at least part of their childhood in this region. Secondly, there does not appear to be any clear relationship between the oxygen and strontium isotope ratios from these samples, nor are there obvious 'cultural' or 'temporal' divisions within the oxygen isotope results as reflected in the strontium data forsomeofthe Middle Iron Age individualsand the individual from the chariot burial. It is important to note that correlations between strontium and oxygen isotope ratios are not necessarily expected, as they are influenced by mutually exclusive variables. Finally, the alsO-depleted (more negative) enamel from individual 825 (Iron Age/Romano~British period) might indicate that this person spent part of their childhood in an area outside the region. 0.722 3. 0.720 0.718 0.716- ,~ 0.714 0.712 Strontium isotope analysis 0.710 Jand Montgomery, Kay Lakin, alld Jalle Evulls 0.708 Human mobility can be investigated by analysing the strontium isotope values of tooth enamel, which mineralises in early childhood kg Cox and Sealy 1997; Ezzo and Price 2002; Montgomery et al 2003; Price et a11994; Price et a/2(02). If a difference can be demonstrated beh,,'een the enamel and that of locally available values obtained from rock, soil, plants, and other humans and animals believed to be of local origin, an individual is deemed to have either originated elsewhere, or to have consumed a (childhood) diet composed predominantly of imported food. However, the age at which they moved is difficult to establish if the move was after enamel mineralization was complete (ie a.round puberty). Tracking the mobility of adults is further thwarted, because the integrity of strontium isotope ratios obtained from other later-forming skeletal tissues such as bone and dentine cannot currently be established (Trickett el aI2003). •••.••••••••••• P~t>ii~'ninil; ~f B,w;h • ,. 4. biosphere values 6. ---~'7a"~~v~~·-----------------2. local cattle raised on !he tirrteslt:xleJl( ~ 0.706'!---::----",,-----=,-----,,----,o 100 200 300 400 500 Sr concentration (ppm) Figure 187: Strout;ultl data for till! second mandibular molars of six Romallo-Britis1l cattle from Site 0 (Ferr.'! FrystollJ The narrow ridge of limestone which the route of the A1 follows is bounded to the east by PermoTriassic mudstones and sandstones, and to the west by the sandstones of the Upper Carboniferous Coal Measures (St'l' ell 1), which can provide biosphere strontium isotope values between 0.709 and 0.714 (unpublished data held by Montgomery and Evans). The strontium values seen in cattle 1, 2, 4, and 6 might thus be explained by origins in Yorkshire, although this does not rule out origins elsewhere in Britainorthe Continent, where such values may also be obtained. Cattle 3 and 5 have strontium isotope values that have not been observed to date in British archaeological animal or human samples (Budd et al 2000; Evans and Tatham 2004; Montgomery 2002; Montgomery el aI2000; 2003; 2(05). Such values are indicative of origins in regions of ancient granites and gneisses (eg Aberg 1995; Grupe el al 1997; Muller et aI2003; Negrel and Pauwels 2004; Sillen et a1199B), which do not occur in significant amounts in England or Wales (British Geological Survey 1979a; 1979b). Strontium isotope data were obtained from six of the cattle from the ditch of the chariot burial (designated cow 1, cow 2, etc) in order to determine if they were from the same herd and whether they \\'ere of local origin. Information was also obtained from the tooth enamel of 12 humans, dating from the Bronze Age through to the Romano-British period, which had been subject to oxygen isotope analysis (see above). The cattle show a very wide range of strontium isotope values (0.71-0.72) that greatly exceeds the variability observed in a single herd of modern cattle (Lakin 2004), and is not consistent with a diet The humans also exhibit a wide range of strontium isotope values (-0.708-0.716) (Fig 186). The Beaker burial (2263), a female Middle Lron Age burial (732), 353 and possibly the Early Bronze Age individual (2023) are consistent with local origins, ie within range of seawater (the source of rainwater) and the Magnesian Limestone (McArthur ef al 2001). However, such values would also be consistent with origins on other marine carbonates such as Cretaceous Chalk. The hvo Iron Age/Romano-British burials from Site Q (825 and 742) have similar strontium values, despite having different oxygen isotope ratios. Such strontium values are not indicative of origins on limestone. Nevertheless, comparable values have been obtained from other human burials in Yorkshire and elsewhere in southern and eastern England kg Montgomery 2002; Cooper 2004), as well as in cattle 1 and 4. The final group has high strontium isotope ratios, and contains only Middle Iron Age individuals from Site M and the chariot burial. As already noted for the cattle, such high values are indicative of origins in regions of old granites and gneisses and exceed the current range of publ ished archaeological human enamel data from Britain (Fig 187). Moreover, similar values are only rarely reported in datasets of archaeological tooth enamel outside Britain kg Sillen ef al 1998; Grupe et (II 1997; Price el af 2002). Consequently, there is currently very little comparative data for archaeological humans or animals agajnst which to compare these individuals and draw sound conclusions about their origins. Conclusions Combining theevidenceavailable from the suiteof isotopes with the overall archaeological context, it is difficult to draw firm conclusions that aid current understanding of the possible movements of Iron Age people across Europe. The results contribute to ongoing research and may help toelucidatequestions generated by the recent work, including how long the cattle spent in the Ferry Fryston area prior to death, the contribution of drift of Scandinavian origin to biosphere values in East Yorkshire, and potential sources of origin for the Middle Iron Age human burials and the two cattle of 'exotic' origin. Sample! Context Description A/fillS Bell/fa COry/liS frax;"us 1/('),' Pomoideae I'rlllll/S QI/CrcllS PopII/I/s! Salix UlI!X! Cytisl/s Ulmus PI/lus £(/1'(1' I1mll:I' Agl' Sill' 0 Werr)' Fryslon) Sample 1, fill 2060 Crcmalion pit 2061, wHhin ring dilch 2068 Sample 2, fill 2134 Fill (segment 2133) in ouler ring ditch 2121 Sample 4, fill 2144 Cremation pit 2145 at centre of ring ditch 111112122 Sample 7, fill 2148 Fill (segment 2149) in inner ring ditch 2122 2 Insufficient charconl for identificiltion , Is,2u Ih, 7s, 2u 5 . - ~ - - (1 1u Middlt' Inm ASl! '" Sile M Sample 6, fill 121 Human burial 120, in 122 e/' Sample 7, fill 100 Fill, pH 99, adjacent to roundhouse 126/1220 3 SampJe66, fill 1470 Fill, post-pit 1408, four-post slructure 2070 - Sample 110, fill 2578 Fill, pit 2058, associated with articulOllcd cow buria12J(J(J 3 8h,8s . - 1 - . . . 2 Tilllf/' 62: CllflnlKl/ /IIwlysis 3u lu 179