SCIENCE ADVANCES | RESEARCH ARTICLE ARCHAEOLOGY Copyright © 2020 The Authors, some rights reserved; Origins of the sarsen megaliths at Stonehenge exclusive licensee David J. Nash1,2*, T. Jake R. Ciborowski1, J. Stewart Ullyott1, Mike Parker Pearson3, American Association 4 5 1 6,7 for the Advancement Timothy Darvill , Susan Greaney , Georgios Maniatis , Katy A. Whitaker of Science. No claim to original U.S. Government The sources of the stone used to construct Stonehenge around 2500 BCE have been debated for over four centuries. Works. Distributed The smaller “bluestones” near the center of the monument have been traced to Wales, but the origins of the sarsen under a Creative (silcrete) megaliths that form the primary architecture of Stonehenge remain unknown. Here, we use geochemical Commons Attribution data to show that 50 of the 52 sarsens at the monument share a consistent chemistry and, by inference, originated NonCommercial from a common source area. We then compare the geochemical signature of a core extracted from Stone 58 at License 4.0 (CC BY-NC). Stonehenge with equivalent data for sarsens from across southern Britain. From this, we identify West Woods, Wiltshire, 25 km north of Stonehenge, as the most probable source area for the majority of sarsens at the monument. INTRODUCTION that sarsen was used to construct megalithic monuments in Kent, The origins of the stones used to build the monument of Stonehenge Dorset, and Oxfordshire [e.g., (18)], it is not impossible that these and their transportation methods and routes have been the subject regions could also have supplied stones for Stonehenge. Furthermore, of debate among archaeologists and geologists for more than four as the distant sources of the bluestones attest, the choice of stone centuries (1–6). Two main types of stones are present at the monument used to construct Stonehenge was far from pragmatic or based simply (Fig. 1). The smaller “bluestones” have attracted the most geological on local availability (14, 19). attention. These stones—which include dolerites, tuffs, rhyolites, Here, we apply a novel combination of geochemical and statis- and sandstones—are clearly not local to Stonehenge, which stands tical approaches, developed and validated on silcretes in southern in an area underlain by Chalk bedrock. Recent studies suggest that Africa (20, 21), to determine the provenance of the sarsen stones at the igneous bluestones originated from the Preseli Hills in southwest Stonehenge. First, we use portable x-ray fluorescence spectrometry Wales [e.g., (7–9)], over 200 km west of the monument, and that the (PXRF) to provide an initial chemical characterization of all extant sandstone Altar Stone came from east Wales (10). However, with sarsen uprights and lintel stones. The resulting data are analyzed the exception of work by Howard (11), no research has been pub- statistically to determine the degree of chemical variability present lished on the sources of the larger sarsens [a vernacular term for the across the monument. We then undertake inductively coupled plasma duricrust silcrete; (12)], erected during the mid-third millennium mass spectrometry (ICP-MS) and ICP–atomic emission spectro- BCE, that comprise the main architecture of Stonehenge (13, 14). metry (ICP-AES) analyses of (i) samples from a recently rediscov- Today, only 52 of the original ~80 sarsen stones remain at the mon- ered core drilled through sarsen Stone 58 at Stonehenge and (ii) a ument. These include all 15 stones forming the central Trilithon representative range of sarsen boulders from across southern Britain. Horseshoe, 33 of the 60 uprights and lintels from the outer Sarsen These analyses are used to generate high-resolution chemical signa- Circle, plus the peripheral Heel Stone, Slaughter Stone, and two of the tures for the monument and potential source regions. Comparisons four original Station Stones. of these signatures allow us to identify the most likely source area Typical sarsen uprights at Stonehenge have a long-axis length of for the sarsens at Stonehenge. 6.0 to 7.0 m (including sections below ground) and weigh ~20 metric tons, with the largest reaching 9.1 m (Stone 56) and having an above- ground weight of ~30 metric tons (Stone 54) (15). Their size, cou- RESULTS pled with the limited occurrence of sarsen boulders on Salisbury Chemical variability within the sarsen stones at Stonehenge Plain today (16), has led to the perceived wisdom that these stones Nondestructive chemical analyses of all 52 sarsens present at Stone- were sourced from the Marlborough Downs (Fig. 1B), 30 km to the henge were undertaken using PXRF. This involved taking five read- north of the monument (17). This view has prevailed since the writ- ings at random positions across each stone, generating 260 analyses ings of the 16th century antiquary William Lambarde (1) but is for 34 chemical elements (see Materials and Methods; full dataset is rarely challenged and has never been rigorously tested. It is certain- provided in data file S1). The PXRF data demonstrate that the sarsens ly true that the most extensive spreads of sarsen boulders in Britain typically comprise >99% silica, with only traces of each of the other today occur on the Marlborough Downs (Fig. 1A). However, given major elements (Al, Ca, Fe, K, Mg, Mn, P, and Ti) present. This high purity is in line with the previous analyses of British sarsens [e.g., (22–24)] and reflects the mineralogy of the stones, which comprise 1School of Environment and Technology, University of Brighton, Lewes Road, Brighton quartz sands cemented by quartz. Ten of the PXRF analyses at the BN2 4GJ, UK. 2School of Geography, Archaeology and Environmental Studies, Uni- monument record anomalously low Si (see Materials and Methods), versity of the Witwatersrand, Johannesburg, South Africa. 3Institute of Archaeology, University College London, 31-34 Gordon Square, London WC1H 0PY, UK. 4Depart- which most likely indicates that nonquartz accessory mineral grains ment of Archaeology and Anthropology, Bournemouth University, Fern Barrow, were excited by the x-ray beam during data acquisition. These read- Poole, Dorset BH12 5BB, UK. 5English Heritage, 29 Queen Square, Bristol BS1 4ND, ings are excluded from subsequent statistical investigations. 6 UK. Department of Archaeology, University of Reading, Whiteknights, Reading Linear discriminant analysis (LDA) and Bayesian principal com- RG6 6AH, UK. 7Historic England, 4th Floor, Cannon Bridge House, 25 Dowgate Hill, London EC4R 2YA, UK. ponent analysis (BPCA) were used to analyze the PXRF data (see *Corresponding author. Email: [email protected] Materials and Methods). BPCA was chosen over standard principal Nash et al., Sci. Adv. 2020; 6 : eabc0133 29 July 2020 1 of 8 SCIENCE ADVANCES | RESEARCH ARTICLE A Sampling sites B 20 Marlborough 1–6. See map (B) Downs 7–8. Mutter’s Moor, Devon 9–10. Valley of the Stones, Dorset 1 2 11. Bramdean, Hampshire Avebury 3 12–14. Brighton area, East Sussex 4 15. Blue Bell Hill, Kent River Kennet 5 16. Lenham Quarry, Kent East Anglian Heights 6 17–18. Gestingthorpe, Essex route 19 s 19. Sudbury, Suffok 17–18 20. Castle Rising, Norfolk Knap Hill son’ n Atki Chilterns Marden H i l Marlborough l ’ s Downs r o u London Basin route t 1–6 e 15 Salisbury Plain New North Downs 16 Rive Sampling sites r 11 Avon 1. Monkton Down Stonehenge 12–14 2. Totterdown Wood South Downs 3. Clatford Bottom 7–8 05km 0 4. Piggledene 5. Lockeridge Dene Sarsen and puddingstone sites 6. West Woods Stonehenge 9–10 Hampshire Common puddingstone areas Basin 05km C Heel Stone D Bank and ditch (Stone 96) 25 26 27 enclosure 28 127 29 Avenue 23 30 North “Barrow” 130 22 60 101 1 122 Slaughter Stone 21 Central sarsen 102 2 (Stone 95) 59a 160a trilithon horseshoe 58 Station Stone 160b (Stone 93) 158 59b 3 120 160c 57 59c Outer 156 sarsen 19 4 Modern access pathway circle Altar Stone 105 56 51 5 55a Bluestone Bluestone 152 circle horseshoe 53 52 55b 107 6 Station Stone 16 154 (Stone 91) 15 54 7 N 14 South “Barrow” 8 Upright sarsen 9a 9b Bank and ditch Fallen sarsen 10 enclosure Sarsen lintel stone 12 11 Sandstone 03m 0 “Bluestone” 01m 0 Fig. 1. Stonehenge in context. (A) Distribution of silcrete boulders across southern Britain, including sarsens and conglomeratic variants known as puddingstone [data from (16, 22, 28, 46, 47)]. (B) Sampling sites and topography in the Stonehenge-Avebury area [areas in pale gray at 100 to 175 m above sea level (asl), and those in dark gray at 175 to 270 m asl], along with proposed transportation routes for the sarsen stones. (C) Plan of Stonehenge showing the area of the monument enclosed by earthworks plus numbered peripheral sarsen stones. (D) Detail of the main Stonehenge monument showing the remaining bluestones and numbered sarsen stones. component analysis (PCA) as the latter has limited utility for zero- introduction of iron and replacement of Si by Ca during late-stage inflated or incomplete datasets (25), both common issues in geo- diagenesis and subaerial weathering; (23)], and Co, Cd, Se, Sb, and chemical studies where many elements are at such low concentrations Sn (which were below detection limits in all PXRF readings). that they fluctuate close to or below instrumental detection limits. Exploratory LDA models indicate significant clustering of the For all statistical analyses, data for the following elements were PXRF data (model accuracy, ~0.25), with most analyses falling within omitted—Si, Ca, and Fe [to avoid potential anomalies caused by the a single cluster (Fig. 2A). We define a sarsen as being statistically Nash et al., Sci. Adv. 2020; 6 : eabc0133 29 July 2020 2 of 8 SCIENCE ADVANCES | RESEARCH ARTICLE AB Fig. 2. Results of the statistical analysis of PXRF data from all 52 sarsen stones at Stonehenge.