VIKING UNST PROJECT: FIELD SEASON 2008 - Nabo

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UND AM151 214 1369 B Orange/red hard baked ashy deposit in southwestannexe.HMR AM152 345 1420 A Red ash hearth sealed by black ash [346] in theannexe, against wall face [009]/[079]HMR AM153 1044 1593 C Bright red area of burning within House 2,associated with areas of black/grey ash.HMR AM154 246 1595 A Area of possible burning on the west side of theupper room of House 1, associated with burntbedrock and fragments of charcoal.Table 5.2: Summary of the archaeomagnetic samples collected from Hamar (HMR) and theUpper House at Underhoull (UND).5.4 TEPHROCHRONOLOGYThe principles behind using volcanic ash (tephra) as a dating technique are based on thedistinctive geochemical properties of the material being specific to a volcanic system.During an eruption, material is ejected into the atmosphere; the majority of this materialwill settle relatively close to the source of the volcano, but fine particles of volcanic ash canbe rapidly dispersed across an extensive area through the atmosphere and formcharacteristic horizons (isochrons) wherever this material is deposited. These horizonsenable the correlation of different areas, linking spatially distinct areas to a common eventin time (Dugmore 1989, 168; Dugmore & Newton 1999, 70; Swindles et al., 2008). Annualdates for the various tephra layers can be obtained through historical records, or wherethese are not available for prehistoric tephras, through complementary dating techniquessuch as radiocarbon or ice-core chronologies (Dugmore et al. 1995, 379; Wastegård et al.2003, 278). The precision of the associated radiocarbon dates have been greatly improvedin recent years through the application of wiggle-matching to the sequences of dates(Swindles et al. 2007, 667). It has been noted that some Holocene tephras can be dated witha decadal accuracy, which clearly exceeds the available precision associated withradiocarbon dating (Hall & Pilcher 2002, 229; Wastegård et al. 2003, 278).Dugmore (1989) was the first to identify the occurrence of tephra within Scotland, butdespite the potential of this technique to both the chronology and palaeoenvironmentalstudies, only limited work has been carried out within Shetland. An assessment of a lakecore from Catta Ness, Lunnasting was carried out by Bennet et al (1992), while aninvestigation of the deposits at Kebister was carried out by Dugmore and Newton (1999,70).A number of tephra layers may have been deposited on Shetland during the periods thatpre- and post-date the settlements at Hamar and Underhoull (Hall & Pilcher 2002, Table 2;Swindles et al., 2008, Table 1.4). The identification of these tephras would constrain thechronological assessment of these sites, as well as allowing the evidence recorded at Hamarand Underhoull to be unambiguously linked to sites across the North Atlantic. Apreliminary assessment of samples collected from the layers of peat sealing the site ofUnderhoull collected during the 2007 excavation season has been carried out (details inOutram et al. 2007, Table 5.2). Analysis of samples SF238 and SF239 demonstrated the66
presence of tephra within the deposit. Further samples were collected during the 2008season, summarised in table 5.3:Sample Context Section Descriptionnumber number991 001/025/026 N-facing section A purple-black well-humified peat withsome silt and clay, with successive layers ofwell-humified peat representing the preandpost-abandonment horizon of the site.The lower deposits are associated with alayer of paving (context [029]) and mayinclude some evidence for soil amendment.992 001/025/026 N-facing section A purple-black well-humified peat withsome silt and clay, with successive layers ofwell-humified peat representing the preandpost-abandonment horizon of the site.The lower deposits are associated with alayer of paving (context [029]) and mayinclude some evidence for soil amendment.993 001/025/026 N-facing section A purple-black well-humified peat withsome silt and clay, with successive layers ofwell-humified peat representing the preandpost-abandonment horizon of the site.The lower deposits are associated with alayer of paving (context [029]) and mayinclude some evidence for soil amendment.Table 5.3: Summary of the monolith samples that will be used to investigate the presenceof tephra within the deposits at Underhoull, Area A.The individual shards of tephra are generally 10-100µm in size, being contained within thematrix of the deposit so that they are not commonly visible with the naked eye, and arereferred to as crypto-tephra (Hall & Pilcher 2002, 224; Dugmore 1989, 169). The presenceof tephra within a deposit will therefore require the samples to be assessed using lightmicroscopy. The samples can then be geochemically assessed using electron microprobeanalysis with the hope of identifying the source, and therefore the date of the materialpresent (Pilcher & Hall 1996, 101). Funding has been obtained from the NaturalEnvironment Research Council (NERC) to use the Tephra Analytical Unit facilities, Schoolof Geosciences, University of Edinburgh in February 2009, where the samples will begeochemically assessed and characterised.67
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VIKING UNST PROJECTEXCAVATIONS AT H
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This is a provisional report on the
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PART TWO: PERSONNEL AND RELATED RES
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PART ONEEXCAVATIONS AT HAMAR &THE U
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A geophysical survey of the site wa
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The 2006 & 2007 excavation seasonsT
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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 and 64: 63Figure 4.1: The graphical represe
Page 65: SitecodeSamplecodeContext SFnumberA
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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