Reflectance Transformation Imaging (RTI) Investigation of Engraved Chalk Plaques from the Stonehenge Region

Bob Davis,Matt Leivers,Phil Harding

doi:10.1017/ppr.2021.13

Abstract

Newly discovered and previously documented Late Neolithic chalk plaques from the Stonehenge locality have been subjected to new, non-invasive techniques which allow access to previously unseen elements of archaeological evidence. The application of these methods – involving Reflectance Transformation Imaging (RTI) and Polynomial Texture Mapping (PTM) – has revealed detail of the surface preparation and allowed methods and sequence of the compositions to be unpicked, clarifying their complexities. The results reveal a range of approaches to the compositions, some of which demonstrate planning, order, and intention while others include less systematic, rapidly executed sketches. Investigations of lines and surfaces have been made, supplemented by preliminary studies of replicated test pieces, to examine potential implements used in their creation and remark on plaque biographies and surface attrition following manufacture. Furthermore, detail revealed by RTI provides indications of the orientations in which some of the plaques should be viewed and – in one instance – suggests a ‘reflected’ element that may not be entirely abstract. Results from improved radiocarbon determinations place the plaques in the early part of the 3rd millennium bc which, together with identification of individual motifs, allows the plaques and the designs to be reconsidered within the corpus of Neolithic art in the British Isles.

Highlights

Chalk has provided a most attractive material for engraving for countless generations
The revised descriptions for Plaques 1 and 2 from the Chalk Plaque Pit summarise the existing descriptions (Harding 1988, fig. 2) with additional data obtained from Reflectance Transformation Imaging (RTI)
The original hand-drawn figures and high resolution photographs which document the plaques from the Chalk Plaque Pit and Butterfield Down provided, and still do, accurate and reliable records of the objects; the results of this project have confirmed that RTI provides an alternative method of illustration which can extract data the importance of which was not fully appreciated previously

Summary

Introduction

Chalk has provided a most attractive material for engraving for countless generations. The four incised plaques (Figs 1 and 2) have all been found within 5 km of one another in a cluster around Stonehenge Those from the Chalk Plaque Pit have been joined by a broken example from Butterfield Down, Amesbury with another fragment from Bulford, only 7 km from Stonehenge. The plaques from the Chalk Plaque Pit (Plaques 1 and 2) were found during road-widening of the A303, west of King Barrow Ridge, in 1968 Both were inscribed with geometric designs and were accompanied by sherds of Late Neolithic Grooved Ware pottery attributed to the Clacton sub-style. The plaque remains undated; Rawlings and Fitzpatrick (1990) made comparisons with the examples from the Chalk Plaque Pit but considered that the design was strongly influenced by Beaker decoration. Lawson (1993) considered that the motifs were more reminiscent of Late Neolithic designs depicted on Orcadian art

Methods

Results

Discussion

Conclusion