New features within the henge at Avebury, Wiltshire: aerial and geophysical evidence.

New features within the henge at Avebury, Wiltshire: aerial and geophysical evidence. The hot and dry summer of 1995 once again proved the value andcost-effectiveness of aerial survey. Numerous parchmarks were a productof the dry conditions throughout England, but especially in chalkgrassland, and they revealed important new archaeological information. Aparchmark within the great Neolithic henge hengeNouna circular monument, often containing a circle of stones, dating from the Neolithic and Bronze Ages [from Stonehenge] at Avebury identifies a newsubterranean feature, confirmed by geophysical survey Geophysical survey refers to the systematic collection of geophysical data for spatial studies. Geophysical surveys may use a great variety of sensing instruments, and data may be collected from above or below the Earth's surface or from aerial or marine platforms. , which fills infurther details of the Avebury enclosure.William Stukeley The Rev. Dr. William Stukeley FRS, FRCP, FSA (November 7, 1687–March 3, 1765) was an English antiquary who pioneered the archaeological investigation of Stonehenge and Avebury and was one of the founders of field archaeology. (1687-1765), one of Avebury's earliestchroniclers, described the great henge at Avebury as 'the noblestmonument, which is probably on the face of the globe' (1743: 37).Despite the attention it has received over the last 300 years (Crawford& Keiller 1928; Smith 1965; Burl 1979), the corpus of informationfor this great earthwork earth��work?n.1. An earthen embankment, especially one used as a fortification. See Synonyms at bulwark.2. Engineering Excavation and embankment of earth.3. and its stone circles, is inadequate (Ucko etal. 1990; Pitts & Whittle 1992). The recent discovery by aerialsurvey of an entirely new structure within the henge emphasizes the needfor continued investigations at all nationally important sites[ILLUSTRATION FOR FIGURE 1 OMITTED].Aerial surveyThe drought conditions "Drought Conditions" is episode 126 of The West Wing. PlotSenator Rafferty, a new presidential candidate garnered much media attention with a ground-breaking speech about health care. of 1995 and the discoveries made throughoutEngland have been published already (Featherstone et al. 1995); here weare able to report on a particular discovery within one ofBritain's most famous and important monuments. One of thechallenges of aerial survey is to keep making new discoveries and itshould no longer be a surprise that sites such as Avebury still havearchaeological features within them which remain to be discovered.The earliest aerial photographs of Avebury held in the NationalMonuments Record were taken on 22 June 1924, the most recent on 8February 1996 (in exceptional snow conditions). In this 72-year periodAvebury and its environs have been surveyed from the air frequently(there are 416 oblique photographs of the site in the NMRC NMRC New Millennium Research CouncilNMRC Naval Medical Research CenterNMRC National Microelectronics Research Centre (University College Cork, Ireland)NMRC National Monuments Record Centre (UK)alone), butuntil August 1995 no aerial photograph showed cropmarks or parchmarkswithin the henge from which an accurate map could be made (although someparchmarks were photographed in 1989 by the National Trust Warden). Themarks, visible on 11 August 1995, were even clearer on I September 1995when Roger Featherstone was flying with a BBC BBCin full British Broadcasting Corp.Publicly financed broadcasting system in Britain. A private company at its founding in 1922, it was replaced by a public corporation under royal charter in 1927. TV film crew and PLATE 1was taken. There were also reports in 1995 that the parchmarks werevisible on the ground (as they had been in 1990, [ILLUSTRATION FORFIGURE 2 OMITTED]) and some were also surveyed by the National Trust in1995. The intensity of the drought in 1995 meant that the buriedditches, in a chalk subsoil subsoilLayer (stratum) of earth immediately below the surface soil, consisting predominantly of minerals and leached materials such as iron and aluminum compounds. Humus remains and clay accumulate in subsoil, but the teeming macroscopic and microscopic organisms that make , produced negative cropmarks in grass (PLATE1; see also Featherstone et al. 1995: plate 4). This is because of theparticular drainage characteristics and particle size Particle size, also called grain size, refers to the diameter of individual grains of sediment, or the lithified particles in clastic rocks. The term may also be applied to other granular materials. of the chalk(Wilson 1982: 55). The grass on the crest of the bank also parches out;in a drought this is a result of the lack of water throughout thegrowing season growing season,period during which plant growth takes place. In temperate climates the growing season is limited by seasonal changes in temperature and is defined as the period between the last killing frost of spring and the first killing frost of autumn, at which .The parchmarks that excite particular interest are in thenorthwestern quadrant: a double-ditched curvilinear curvilineara line appearing as a curve; nonlinear.curvilinear regressionsee curvilinear regression. feature seen beyondthe western end of the garden of The Lodge and (faintly) in the gardenitself [ILLUSTRATION FOR FIGURES 2 AND 3.4 OMITTED]. There appears to bean inner feature, possibly rectangular, which may have a central pit fora post or stone. Three stone holes of the Northern Inner Circleimmediately to the east of the new enclosure, are also visible; thesewere located by a previous geophysical survey (Ucko et al. 1990: plate67A). In the northeastern quadrant, parchmarks of a further 11 stoneholes of the Northern Inner Circle are seen, four of which were recordedduring a survey of the earthworks carried out by the RCHME RCHME Royal Commission on the Historical Monuments of England (UK)in 1990, andseveral by previous geophysical survey (Ucko et al. 1990: plates 67A& 73).In the Outer Circle, 17 stone holes are visible as parchmarks in thenortheastern and southeastern quadrants of the henge. In thesoutheastern quadrant there are 10 possible stone holes of the SouthernInner Circle visible as parchmarks. In addition, between the SouthernInner Circle and the southern entrance to the henge, there are two markswhich possibly indicate former stone holes. The northern one of thesemight, with the 'ring stone' (Smith 1965: figure 68), make apair of stone holes equidistant e��qui��dis��tant?adj.Equally distant.equi��distance n. between the Outer Circle and theSouthern Inner Circle where they might in some way be related to thesouthern entrance.The transcription [ILLUSTRATION FOR FIGURE 2 OMITTED], compiled at ascale of 1:1000, has been overlain o��ver��lain?v.Past participle of overlie. on the RCHME earthwork survey; allthe features visible as parchmarks on photographs taken by the RCHME (inAugust and September 1995) were included.Why has it taken so long for parchmarks at Avebury to show? 1995 wasa drought year - but there have been drought years before; it may havebeen the sheep-grazing. The flock had just grazed this quadrant and leftthe grass short, thus making the parchmarks more visible.Geophysical surveyThe results of previous geophysical investigations by the AncientMonuments Laboratory at Avebury have been described by Ucko et al.(1990). Resistivity resistivityElectrical resistance of a conductor of unit cross-sectional area and unit length. The resistivity of a conductor depends on its composition and its temperature. surveys on the course of the West Kennet Avenue Kennet Avenue or West Kennet Avenue is a prehistoric site in the English county of Wiltshire.It was an avenue of two parallel lines of stones 25m wide and 2.5km in length which ran between the Neolithic sites of Avebury and The Sanctuary. andin the southeast and northeast quadrants of the henge have detectedformer stone holes. This method of survey can detect buried pits andditches when local soil moisture contrasts are favourable. Magnetometersurvey, which can also detect the latter, had not proved so effective atlocating former mega-lithic settings (except where these are marked byburning pits); ferrous litter and service trenches in the vicinity ofbuildings also reduce its effectiveness.Both resistivity and magnetometry were used over the central featurelocated by aerial photography This article or section may contain original research or unverified claims.Please help Wikipedia by adding references. See the for details.This article has been tagged since September 2007. (see PLATE 1 & [ILLUSTRATION FORFIGURE 2 OMITTED]). Resistivity survey was then extended throughout thequadrant in order to place the new feature in a wider spatial context toaid its visual definition against a wider background area. It was alsoclearly of value to use this opportunity to build upon the coverage ofthe entire monument, still far from complete despite the efforts ofprevious years. The magnetometer readings over the feature were renderedvery erratic by ferrous litter in the rear of the gardens and yards. Nomagnetic anomalies of potential archaeological value were discerniblethrough this superficial disturbance.The resistivity survey, conducted with a Geoscan Research RM15 meter,PA5 probe array and MPX MPX - Multiplexor Channel 15 multiplexor, was more successful. Readingswere taken at 0-5-m intervals over the feature, including that part ofit evidently contained within the garden of The Lodge. The TwinElectrode configuration was used and at each position a reading waslogged with a mobile probe spacing of 0.5 m. Readings were also takenusing a mobile probe spacing of 1.0 m at intervals coming or happening with intervals between; now and then.See also: Interval of 1.0x0.5 m. For thearea concerned there are therefore two sets of resistivity data, forcomparison against each other: the 1.0m probe spacing having a deeperpenetration (approximately 1.5 m) than the 0.5 m spacing (approximately0.75 m). Beyond the area of the feature itself, the sampling intervalwas widened to 0.5x1.0 m, with a probe spacing of 0.5 m. The greytoneplots [ILLUSTRATION FOR FIGURE 3 OMITTED] collate col��late?tr.v. col��lat��ed, col��lat��ing, col��lates1. To examine and compare carefully in order to note points of disagreement.2. To assemble in proper numerical or logical sequence.3. the most expressivedatasets for the entire survey of the quadrant: FIGURE 3.1 the raw data,3.2 after contrast enhancement, 3.3 after directional filtering, 3.4drawing attention to resistivity anomalies.As well as the three former stone holes relocated on the circuit ofthe Northern Inner Circle (see also Ucko et al. 1990: plate 67), severalother resistivity anomalies deserve comment. The new central feature inthe northwestern quadrant is confirmed, although its definition[ILLUSTRATION FOR A ON FIGURE 3.4 OMITTED] is very weak. The resistivitydata do not show that it is double-ditched, or that it is sub-angular inshape. Set alongside the sharper definition provided on the aerialphotographs [ILLUSTRATION FOR FIGURE 2 OMITTED], however, thedouble-ditched northeast corner, at least, becomes apparent[ILLUSTRATION FOR FIGURE 3.2 OMITTED]. No anomaly corresponds to thecentral feature visible on the aerial photographs. The data from withinthe garden of The Lodge, confused by more recent wall foundations andservice trenches, reveal only the barest hint of the ditch circuit here.The data from the 1.0-m mobile probe spacing do not appear significantlydifferent from those of the 0.5-m spacing. Given previous experience atthe site, such imprecise results are hardly surprising.A number of features located by the resistivity survey have notpreviously been detected by any antiquarian an��ti��quar��i��an?n.One who studies, collects, or deals in antiquities.adj.1. Of or relating to antiquarians or to the study or collecting of antiquities.2. Dealing in or having to do with old or rare books. commentator or by moderntopographic survey. These are labelled B-G on FIGURE 3.4. (B, C and Gwere also visible on the aerial photographs). B, C and D, in thesouthwestern corner of the quadrant, are low-resistance anomaliesindicating ditches. B could be a small enclosure abutting the interioredge of the Outer Circle; there may be an entrance on its northern side.C and D are ditches, about 28 m long, running approximately north -south at a slight angle to each other, each with a deflection to thewest, or a corner, at their northern ends; these are perhaps parts offormer enclosures, too. C coincides, in part, with a linear depressionrecorded by the RCHME field survey.The next linear anomaly, E, is apparently a ditch, having an originnear the centre of the quadrant, running northwards and then after some20 m angling northwestwards for another 50 m before losing itsdefinition close to Stone 41. It crosses a very well-defined edge thatdemarcates a broad zone of relatively low resistance readings (F), up to15 m wide, which runs along the inner perimeter of the Outer Circle -contrasting with the higher resistance values of the core area of thequadrant. Its inner edge is most strongly defined opposite Stones 40-42.This zone of low readings (suggestive of suggestive ofDecision making adjective Referring to a pattern by LM or imaging, that the interpreter associates with a particular–usually malignant lesion. See Aunt Millie approach, Defensive medicine. damper and/or deeper soil) isnot explained by any previous land-use arrangement or feature visible onthe surface. No matching anomaly is known in either the northeast or thesoutheast quadrants (Ucko et al. 1990: plates 66 & 67). The lineardisturbance which clearly marks the boundary between Stukeley'sPasture III and IIII [sic] appears to respect this zone (F), althoughStukeley is clear in all his plans that the pasture boundary extended toStone 43. The linear ditch (E), which clearly disregards F, is perhapsan earlier feature.Another unexplained resistivity anomaly, G, also visible on theaerial photographs [ILLUSTRATION FOR FIGURE 2 OMITTED], could be aditch. It crosses the southeast corner of the quadrant, passing just tothe north of the Northern Inner Circle, and is known to extend into thenortheast quadrant (Ucko et al. 1990: plate 67). From the aerialphotographs it appears to extend southwest, parallel to the eastern sideof enclosure A. G is apparently joined with a kinked linear feature onits south-eastern side, although the geophysical response to the latter(a high resistance anomaly) suggests that it is a different and perhapsmore recent feature. Other linear features detected include relativelyrecent wall and fence alignments running between the stones and justwithin the Outer Circle. A further pasture boundary, parallel to thatrecorded by Stukeley, appears to divide his Pasture III into two.Probably corresponding with the boundary marked on the Inclosure map of1794 (Ucko et al. 1990: plate 47), this is set slightly to the east ofthe former line of elms, the boles of which still survive in places.DiscussionResistivity survey, confirming a sub-surface feature identifiablewith the double-ditched enclosure seen on the 1995 aerial photographs,has located this accurately at ground level. The survey data provide noinformation on the age, character or state of preservation of thefeature. Its location, in terms of height, is within a metre of thesummit of a knoll shown on the contour plan of Avebury (around themodern pub and central road-junction); its place on that higher groundwithin the henge, but in no special place in relation to the standingstones standing stones:see megalithic monuments. , may hint at a pre-henge date. The new central feature may beNeolithic (or later) in age; it resembles the oval barrow at Abingdon(Bradley 1992; Wilson 1982: figure 50), which held a burial. Furtherwork should clarify its date and function; it might be Roman orimmediately post-Roman in date.Excavation, detailed augering and further geophysical survey couldprovide more information on the profiles of the encircling ditches andalso add detail to the possible 'burial' feature at theircentre. Both resistivity profiling (e.g. Szymanski & Tsourlos 1993)and ground penetrating radar (e.g. Goodman & Nishimura 1993, but seealso Meats & Tite 1995) might be appropriate. Sharper resistivityresults might be obtained by surveying at differing times of the year assoil-moisture contrast varies.Perhaps more than any other prehistoric site in Britain, ourknowledge of Avebury has been informed and influenced by the antiquarianrecord. The major record for Avebury is the surviving plans and writtentexts by John Aubrey (1626-1697), and his antiquarian successors, whichdescribe the upstanding surface features and stone holes which wereactually visible in the 17th and 18th centuries. Subsequent excavations,in the 19th and 20th centuries, have been heavily influenced by thisearlier record which was itself very much modelled by the personalities,preconceptions, and intellectual climate of the times (Ucko et al.1990); stones have been recovered and re-erected so as to make the placelook as it did to Stukeley. Prior to the last decade no physicalexamination of the site, with the one exception of Stuart Piggott'sunsuccessful search for a third Inner Circle in 1960 (Piggott 1964), hadexplored much beyond the immediate vicinity of extant and obviousfeatures, and their apparent patterns, as elicited from the survivingantiquarian writings and plans. The results of the aerial andgeophysical survey not only add new information but also increase ourconfidence in the presence and layout of the Inner Circles and theexistence of other stone holes.These latest discoveries of an entirely new and unanticipated featurewithin the core of the henge itself, and of several other unexplainedfeatures as well, underline how inadequate our historically basedinterpretations of nationally important sites are. As well as furtheraerial survey when conditions are good, detailed geophysical coverage isneeded of all the areas remaining unsurveyed, especially the southeastquadrant and the eastern parts of the northeast and southeast quadrants.As the recent survey has very clearly demonstrated, aerial survey andgeophysical methods are capable of revealing and confirming significantnew features as well as extending knowledge of existing patterns.Note. Information on the geophysical surveys can be accessed via theEnglish Heritage Geophysical Survey Database(http://www.eng-h.gov.uk/SDB). The aerial photographs and moreinformation relating to the RCHME surveys are available at the NationalMonuments Record Centre, Kemble Drive, Swindon SN2 2GZ. E-mail:info@rchme.gov.ukAcknowledgements. We are grateful to the National Trust staff,especially Chris Gingell, for his co-operation, and for allowing accessand use of every facility on site. For the geophysical survey we arevery grateful to Roger Bolton for allowing us access to survey withinhis garden. For the aerial survey thanks are due to all the staff in theNMR NMR:see magnetic resonance. Air Photographs library, to Cathy Stoertz for her interpretativeoverview of the plan and to Mark Corney for his helpful comments andsuggestions. Without the graphical expertise of Deborah Cunliffe, FIGURE2 would not have been possible. We are also grateful to Humphrey Welfarefor his comments and support.ReferencesBRADLEY, R. 1992. The excavation of an oval barrow beside theAbingdon causewayed enclosure, Oxfordshire, Proceedings of thePrehistoric Society 58: 127-42.CRAWFORD, O.G.S & W. KEILLER. 1928. Wessex from the air. Oxford:Clarendon Press.FEATHERSTONE, R., P. HORNE, D. MACLEOD & R. BEWLEY. 1995. Aerialreconnaissance in England, summer 1995, Antiquity 69: 981-8.GOODMAN, D. & Y. NISHIMURA. 1993. A ground radar view of Japaneseburial mounds, Antiquity 67: 349-54.MEATS, C. & M. TITE. 1995. A ground penetrating radar survey atRowbury Copse banjo enclosure, Archaeological Prospection 2: 229-36.PIGGOTT, S. 1964. Excavations at Avebury 1960, WiltshireArchaeological Magazine 59: 28-9.PITTS, M. & A. WHITTLE. 1992. The development and date ofAvebury, Proceedings of the Prehistoric Society 58: 203-12.SMITH, I.F. 1965. Windmill Hill and Avebury. Excavations by AlexanderKeiller, 1925-39. Oxford: Clarendon Press.STUKELEY, W. 1743. Abury: a Temple of the British Druids. London.SZYMANSKI, J.E. & P. TSOURLOS. 1993. The resistive resistive/re��sis��tive/ (re-zis��tiv) pertaining to or characterized by resistance. tomographytechnique for archaeology: an introduction and review, ArchaeologiaPolona 31: 5-32.UCKO, P.J., M. HUNTER, A.J. CLARK & A. DAVID David, in the BibleDavid,d. c.970 B.C., king of ancient Israel (c.1010–970 B.C.), successor of Saul. The Book of First Samuel introduces him as the youngest of eight sons who is anointed king by Samuel to replace Saul, who had been deemed a failure. . 1990. Aveburyreconsidered; from the 1660s to the 1990s. London: Unwin Hyman.WHITTLE, A. 1991. A Late Neolithic complex at West Kennet, Wiltshire,England, Antiquity 65: 256-62.WILSON, D.R. 1982. Air photo interpretation for archaeologists.London: Batsford.