VIKING UNST PROJECT: FIELD SEASON 2008 - Nabo

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5. DATING AT HAMAR AND THE UPPER HOUSE, UNDERHOULLZ. Outram, C.M. Batt, G.T. Swindles, & M. Church5.1 OBJECTIVES OF THE DATING PROGRAMMEThe main aim of the dating programme of the Viking Unst Project is to provide a preciseabsolute chronology for the development of the sites under assessment. This is seen as anessential part of the overall research agenda and is particularly important given that thereare relatively few scientific dates produced for the North Atlantic during the Viking andNorse periods (Jansen 1972, 30; Fridriksson & Vésteinsson 2003). Dating these structuresis crucial for answering the research questions proposed as part of the Viking Unst Project.Without accurate dates we cannot begin to build a model for Scandinavian settlement andsociety on Unst or to relate it to other North Atlantic sites.In addition to the archaeological dating methods of stratigraphy and typology, threescientific dating techniques have been employed at the sites of Hamar and Underhoull;AMS radiocarbon dating, archaeomagnetic dating and tephrochronology.5.2 AMS RADIOCARBON DATINGAMS radiocarbon dating forms the major component of the dating strategy. Contexts fordating have been selected by J. Bond, Z. Outram, C. Batt, G. Swindles and M. Church.Decisions were based on the availability of suitable material, the integrity of the depositand the importance of its position within the stratigraphic sequence. It was noted that thedeposits excavated during the 2006 season at Hamar were heavily bioturbated, possiblycompromising the security of the contexts in terms of movement of residual/intrusivematerial through the sequence of deposits. It was concluded that the selection of materialfor radiocarbon dating should be weighted towards the deposits sampled during the 2007and <strong>2008</strong> season, with the exception of the deposits at the base of the trench first excavatedby Stummann Hansen (2000) and selection and preparation of samples is ongoing.The AMS technique allows small samples to be dated, reducing interpretive difficulties dueto contamination, delayed use and residual material. The main material which used ischarred barley grains due to the short-lived and seasonal nature of the grains. The grainshave been obtained by flotation of carefully excavated samples (see Section 4.1). Theresults of the radiocarbon dating are calibrated using the Oxford Radiocarbon Acceleratorunit programme OxCal v.3.10 (Bronk Ramsey 2005) that utilises the most recent Reimer etal. (2004) calibration curve (INTCAL04) and, where appropriate, Bayesian models will beused to interpret the results. The final results will be presented in appropriate academicpublications.A total of six radiocarbon dates have been produced to date, five from Hamar and one fromthe Upper House at Underhoull, summarised in table 5.1. There is a good agreementrecorded for the dates from the different areas sampled at Hamar, and they are broadly asexpected, but further dating evidence is required to enable questions regarding the length ofuse of the site to be investigated more fully.64
SitecodeSamplecodeContext SFnumberArea Uncalibrateddate (BP)Calibrated date(95% confidence)HMR GU-16692 089 075 A 950±30 AD1020-1160HMR GU-16693 165 350 A 945±30 AD1020-1160HMR GU-17734 306 864 A 900±30 AD1030-1220HMR GU-16694 261 849 C 310±30 AD1480-1650HMR GU-16695 305 841 C 365±30 AD1440-1530 (51.5%);AD1540-1640 (43.9%)UND GU-17733 026 994 A 970±30 AD1010-1160Table 5.1: Summary of the AMS radiocarbon dates produced for Hamar (HMR) and theUpper House, Underhoull (UND)The date produced from the Upper house, Underhoull samples Sphagnum leaves and stemscollected from the peat that directly seals the archaeological deposits in the west of Area A.The date therefore relates to the onset of peat development in this area, being an importantevent in the life of the site. However, this date should be regarded as preliminary untilfurther dating evidence can be produced to support it.5.3 ARCHAEOMAGNETIC DATINGThe method of archaeomagnetic dating assesses in situ burnt features in terms of the lastheating event recorded by the magnetic minerals within the clay.Standard sample collection methods were carried out by attaching a plastic referencemarker to the feature with fast-setting glue or the insertion of plastic tubes into soft deposits(Clark et al. 1988, 655-7). The samples were orientated in the present geomagnetic fieldusing a magnetic compass. Magnetic direction is determined in the laboratory using aspinner fluxgate magnetometer and the stability of the sample is assessed using alternatingfielddemagnetisation. The stable magnetic direction is calibrated using the UK calibrationcurve to give a calendar date at 95% confidence (Clark et al. 1988; Batt 1997) as well asthe most recent calibration curve, Rendate (Zananiri et al. 2007).A total of seven features were sampled for archaeomagnetic dating during the <strong>2008</strong> season;four from the Upper House at Underhoull and three from the structures at Hamar. Work isongoing but the samples are summarised in table 5.2:Site Sample Context SF No. Area DescriptioncodeUND AM148 216 1019 A Bright red ashy deposit sealed by [093],marking a possible burning event andcontaining a large quantity of fuel ash slagUND AM149 166 1365 B Putative hearth in south east annexe, reddishorange spread of burning containing manycarbon flecks.UND AM150 166 1367 B Putative hearth in south east annexe, reddishorange spread of burning containing manycarbon flecks65
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VIKING UNST PROJECTEXCAVATIONS AT H
Page 3 and 4:
This is a provisional report on the
Page 5 and 6:
PART TWO: PERSONNEL AND RELATED RES
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PART ONEEXCAVATIONS AT HAMAR &THE U
Page 9 and 10:
A geophysical survey of the site wa
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The 2006 & 2007 excavation seasonsT
Page 13 and 14: sites are multiperiod settlements s
Page 15 and 16: more complex; geophysics would be a
Page 17 and 18: floor surface included fragments of
Page 19 and 20: Lower room & ash pitWork also concl
Page 21 and 22: Figure 2.2: Plan of the sunken floo
Page 23 and 24: External DepositsA section was exca
Page 25 and 26: along the north edge (open side) of
Page 27 and 28: Figure 2.5: The south east annexe,
Page 29 and 30: At the lower (easternmost) end of t
Page 31 and 32: 3. SUMMARY OF FINDS FROM THE 2008 S
Page 33 and 34: 46mm) with working marks on three s
Page 35 and 36: 3.2.2 A geological assessment of th
Page 37 and 38: minerals are chemically stable in n
Page 39 and 40: the same stone. SF721 (context [117
Page 41 and 42: context [185] is a fine example of
Page 43 and 44: close proximity of steatite outcrop
Page 45 and 46: oom. The three body sherds are fair
Page 47 and 48: Greenland and Iceland that a number
Page 49 and 50: channel changes from U-shaped to V-
Page 51 and 52: 4. ENVIRONMENTAL EVIDENCEJ.M. Bond,
Page 53 and 54: The cereals recovered are hulled si
Page 55 and 56: five barley grains and a single oat
Page 57 and 58: 4.3.2 The Upper House, UnderhoullAs
Page 59 and 60: [176]. The identification of microl
Page 61 and 62: iron within the soils (Gaffney & Ga
Page 63: 63Figure 4.1: The graphical represe
Page 67 and 68: presence of tephra within the depos
Page 69 and 70: has been widely criticised as too g
Page 71 and 72: Outram, Z., Cussans, J.E., Summers,
Page 73 and 74: Level Two StudentsKirsty BennellJoh
Page 75 and 76: 8. BIBLIOGRAPHYAlsvik, H. and Batey
Page 77 and 78: Davidson, D.A. and Simpson, I.A. 20
Page 79 and 80: McDonnell, J.G. 2000. Pyrotechnolog
Page 81 and 82: 700s-800s: a potential alternative
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VIKING UNST PROJECT: FIELD SEASON 2008 - Nabo

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