Unravelling the Gordian Knot: Integrating Advanced Portable Technologies into the Analysis of Rock-Art Superimposition

Lead Research Organisation: University of Central Lancashire
Department Name: Sch of Forensic and Investigative Sci


For thousands of years and across the globe, humans have painted images in caves and on other stone surfaces. Some painted sites were later revisited by people who added new paintings on top of the older. Such sites can be very colourful, complex assemblages of paintings placed one on top the other, so much so that it can be very difficult to discern the sequence of painting over very long periods of time. While archaeologists have developed many sophisticated theories to interpret these paintings, and pieces of the paintings that have fallen off may be recovered to analyze in a laboratory, until recently it has been very difficult to analyse the paintings using powerful scientific equipment while the paintings remain on the rock surface. However, technolgoical advances have produced small transportable devices which now allow for detailed on site analyses that do not harm the paintings. These non-destructive portable technologies can scan the cave, rock-surface, and paintings in 3-Dimensions; can use X-ray technology to determine the chemical elements used to make the pigment that makes the painting; laser instruments to identify organic components of the paintings; and can use portable digital photography to reveal hidden layers normally barely perceptible to the human eye. Unravelling the Gordian Knot Project will apply all of these methods to analyze the spectacular and colourful paintings at the site called Pleito, found in California, USA. Pleito is one of the most complex painted sites in the world. It has hundreds of individual paintings with many colours, including different shades of red, black, white, yellow, orange, green, and blue. This is the widest colour palette of any known site in North American and, importantly, it has multiple panels where paintings have been placed over earlier ones. This kind of overpainting, known as superimposition, presents the greatest challenge to rock-art researchers in their attempts to understand painted art found in the landscape. Even though such complex paintings are challenging, they offer to the archaeologist who can unravel the sequence the greatest chance of understanding the development of paintings through time. Within the site of Pleito, a panel known to researchers as the 'Gordian Knot' is the most elaborate panel found there, making it one of the most complex prehistoric panels found anywhere in the world. The name of this project is derived from this panel, and so Pleito and its complex sequences of overpainting executed in various colours is an ideal case to disentangle the history of painting events. The method employed will integrate a range of portable technologies including portable X-Ray Fluorescence, portable Raman Spectroscopy, Highlight Reflectance Transformation, dStretch digital photography, and portable digital laser scanning to unravel the sequence of painting that makes up one of the most complex sites found anywhere in the world. These techniques will help address questions concerning traditions of pigment use and give insights into the role of the art within Native society. The project includes a state-of-the-art website with a 3-D recreation to be housed at the California State University, Channel Islands, offering an alternative to site visitation as a means to experience the site without risk of damaging the ancient paintings. Also, a new conditional assessment will compare degradation of the site to a 2003 baseline report to see how much of the paintings have recently eroded away: finally, a series of experiments combining different pigments with different types of binding agents will give us material to test with both lab based and portable equipment in the creation of a spectral database: this will give us a series of different chemical readings to compare with the actual paintings and allow researchers across the world to compare results from their discoveries with the Gordian Knot Spectral Databasee

Planned Impact

The Gordian Knot Project will have impact across a wide range of different audiences:

Website: This website will be a vehicle for impact including A) Virtual Reality Remote Site Experience; B) Multiple Narrative Viewpoints; C) Spectral Database access; D) Native American Voices; and E) Management Options.
This website will be designed with will include a virtual reality 3-D model of the site and the rock-art, and maintained at the California State University, Channel Islands. Derived from the 3-D scan data, layer separation graphics from Photoshop, and data from the pXRF and pRaman, a virtual reality model complete with specific dropdown menu options for panels, sequences, and individual element compositions will be created. Individual panels and the layers comprising them will be able to be explored, with chemical descriptions in lay and technical terms provided. This will allow for anyone with internet access the opportunity for a virtual experience of the site without the potential harm to the paintings that physical access risks. The inclusion of two optional narratives: one a lay narrative, the other containing the technical data, will allow for users with different needs and levels of knowledge to comprehend the results of the project. Equally, the site will house the Gordian Knot Spectral Database - a comprehensive list of the results of the spectral work which will be usable for researchers across the globe. With its permanent housing, future data will be able to be added, thus making it an expandable data base and add lasting project legacy. Another feature of the site will include a Native Americans Voices page, thus providing a venue for this important stakeholder group that often does not find a place in academic research for input: this section will include voice and video interviews with the local Native American groups to promote indigenous perspectives on the site and its importance within local traditions. Conservation ethos: The main ethos of the website will be to promote conservation and long term care of Pleito as an example of a precious, world class rock-art site to promote long term changes in the attitudes of the general populace in terms of site preservation. This ethos reflects the Wind Wolves Preserve mission statements of preservation and conservation of the natural environment. The website will also act as a management tool to mitigate visitation while promoting the long term aim of preservation of both the site and other archaeological sites found on its property.

The Gordian Knot Project will also provide a site management plan to the Wind Wolves Preserve in order to more fully protect Pleito in the long term. In 2003, the Rock Art Documentation Group (RAD Group) published a technical conditional assessment of the pictographs and the host rock. The RAD Group will work with The Gordian Knot project as consultants to reassess the site: this will give us an assessment of the potential damage that has occurred to the site in the intervening decade. Robinson and Perry have extensive experience with Cultural Resource Management reports and the site will edited the final report before submission to the Wind Wolves Preserve. The report will include management recommendations for the long term preservation of the site. In addition, the project will produce a pamphlet outlining the archaeology of the Preserve and the importance of conservation for a younger, non-academic audience. This pamphlet will be written by Robinson and Perry, and will include. A pdf of the brochure will be provided for the preserve so that it may use in its educational program.

The project will work closely with B&W Tec to aid in the refinement of future portable spectral technologies. A white paper outlining this will be made freely available on the Gordian Knot Website and we will apply for further funding to host a conference to reach a broad spectrum of UK professionals.


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Title PleitoVR 
Description This is an immersive virtual reality prototype combining a suite of innovative features including fully immersive and interactive dStrech representations of the cave and its rock art, baskets, a bow and arrow scene, co-location, ambient sound from the cave environment, and Native American singing. 
Type Of Art Artefact (including digital) 
Year Produced 2019 
Impact PleitoVR is now utilized by Robinson in teaching delivery in undergraduate teaching, plus the landowners (the Wind Wolves Preserve) and the Tejon Indian Tribe in delivering their cultural and educational programmes. It also underpins two publications which are listed as output in this submission, but also I provide a doi to one of the publications in the Digital Object Identifier space below. 
URL https://academic.oup.com/iwc/article/31/2/167/5470140
Description We have successfully detailed the painting sequence through time of one of the most elaborate prehistoric sites in the world at Pleito Cave in California, USA. We used scientific techniques of digital photography and image analysis called Reflective Transformation Imaging, dStrech, laser scanning, and photogrammetry to show over 900 individual painting events that make up the rock paintings. Many of these are painted one on top of another (called superimposition) so our techniques were able to disentangle the paintings in our images and create a sequence through time. We also used trialled these same techniques to analyse prehistoric basketry from the area, showing how imaging techniques can reveal technical aspects of how the baskets were made. But with the rock art, we used portable instruments to analyze the chemical make up of the paintings to determine what the pigment recipes were. We used portable X-Ray Flourescence, Fourier-Transform Infrared Spectroscopy, and portable Raman instrumentation which enabled us to detail different organic and inorganic constituents of the paintings throughout the sequence. Through an experimental approach we are able to developed a mathematical model tracking different specific pigments usage across the site and throughout the over painted sequence. Furthermore, we integrated much of this data into a Virtual Reality platform allowing interactivity with the rock art and our data in entirely innovative ways. Additionally, we applied these same techniques to other nearby sites, such as Pinwheel Cave where we identified hallucinogenic substances through analysing fibrous material found at that site. This included identifying the alkaloid compound atropine and scopolamine through a technique called Liquid Chromatography-Mass Spectometry and cross verified with Scanning Electron Microscopy. The project also developed a micro-viewshed Geographic Information Systems method of on site analyses and applied photogrammetry and Reflective Transformation Imaging to the analysis of basketry material.
Exploitation Route The methodology which we developed to analyse superimposed rock paintings will be highly useful to any other researchers across the globe who work with complex rock paintings. This also is a technique which would be of use to any researcher interested in analysing any complex paintings, such as wall murals, paintings on artefacts, portraits/canvass paintings, graffiti,etc. The GIS approach to micro-viewsheds is likewise not only applicable to rock art and archaeological situations, but could be utilised in architectural analyses and landscape planning. The method of robustly identifying and verifying materials as containing the hallucinogenic alkaloids such as atropine and scopolamine is also transferable to the analysis of any organic material suspected of containing those alkaloids such as other cultural sites or even contemporary policing approaches. The VR platform pipeline that we developed also is also useful to the development of any other cultural heritage context where 3D recreations combine with analytical data to give an enhanced experience of sites and scientific research. This potentially can contribute to creative economy and business opportunities in computer gaming as well as heritage industries, land owners who want to create recreational activities in immersive ways, in addition to pedagogical applications in the classroom. Likewise, this VR aspect with the recreation of sites of great importance to Indigenous organisations and individuals where they may benefit from immersive engagements with places of cultural significance. Furthermore, the RTI analysis of basketry is an innovative way of approaching perishable artefacts with wide potential application in in situ, post excavation, and museum archival research and conservation.
Sectors Creative Economy,Digital/Communication/Information Technologies (including Software),Education,Leisure Activities, including Sports, Recreation and Tourism,Culture, Heritage, Museums and Collections,Pharmaceuticals and Medical Biotechnology

Description Our research has had significant impact with the landowners of the site (the Wind Wolves Preserve) and especially the local Native community known as the Tejon Indian Tribe. The majority of the Tejon community had not previously visited the Wind Wolves Preserve. In a series of expeditions (in 2017/18/19), total of 80 tribal members) requiring 4x4 access, Robinson re-introduced the Tejon tribe to these ancestral places and to the lands of the San Emigdio Mountains including Pleito Cave. This enabled tribal leaders to perform traditional songs and ceremonies, a vital component in Native American practice and to make the sites culturally alive again. This also enabled the Tejon to view their ancestral rock paintings, as well as see their ancestors' artefacts in situ.. During these visits the tribal youth were able to climb on the rocks, to see the artistry of their ancestors, and to experience being in this traditional landscape for the first time. This is vital for the long-term re-connection of people and place in this landscape. Importantly, the discovery of a summer solstice event at Pinwheel Cave in 2016. This discovery was communicated to the Tejon as part of these expeditions and this has had the impact of creating a new sacred tradition for the Tejon so that they now visit this location every summer solstice. Our research has also enabled the Tejon tribe to work directly with the Wind Wolves Preserve. The Tribe now has long-term access to the Preserve independent of our direct involvement enabling them to enabling them to move forward independently in engaging with their own ancestral past. The tribe now communicates and works with the Preserve to gain access to their lands and have participated on the WWP's Annual Spring festival every year since 2017. This is direct evidence for the empowerment of the Tejon in engaging with their own ancestral landscape. In addition to this Robinson ran a rock-art stewardship workshop for members of the Tribes Heritage committee where they co-created a stewardship training programme comprising a training film and guide so that the Tribe can begin to look after the rock-art sites on the Preserve on their own. Impact 2: The co-production of innovative Virtual Reality environments and films: the Gordian Knot team has generated high-end Virtual Reality recreations of the fragile rock-art site of Pleito.. Robinson has provided a VR setup to the Tejon Tribe as a portable immersive museum, giving members of the community unhindered virtual access to Pleito and some of the imaging data we acquired. The impact of this was measured through a survey of 22 tribal members which showed that the VR application had profound personal value for the users: One tribal member stated 'I liked that you could get close to and look at the painting without going there, thus not impacting the site'. Regarding the baskets, one stated, 'Picking up the basket and getting goose bumps when I did pick it up' while another said 'to hold and look at baskets from ancestors was mind-blowing'. Following on from this, a series of VR workshops took place with Tejon members (2017/18/19, 70 participants) who are now co-producing new iterations with us, including the recording of Native songs in their traditional language into the VR model for tribal members to learn the songs and lost languages themselves. The significance of this impact is that it empowers the Tejon Tribe to participate in the creation and dissemination of this via this immersive platform. The tribe has been using the VR in their offices for their own educational purposes, and it has been used at the WWP Nature Festival (see below) to educate non-natives. The Tejon also participated remotely from their offices in Bakersfield in the VR application in a presentation at the Society for American Archaeology Meetings in Washington DC. This event was the first ever co-location VR presentation at the SAAs which not only included the Tejon Tribe but also co-presenters from the Wind Wolves Preserve, the UK, and in Washington DC. Avatars of each participant appear in the VR recreation of Pleito Cave enabling a live stream conversation to include audience members on the relative merits of VR platforms for tribal and land owning agencies to consider. Our field project at Pleito have also incorporated documentary film making of the archaeological processes, results, and social context of the fieldwork. This work has engaged local independent filmmakers as well as collaborating with the UCLAN led Storylab project. We have run two film making workshops in 2018 and 2019 with the Tejon tribe, Preserve staff and students to enable them to develop their own audio/visual perspective of storytelling related to the landscape and archaeology of the Preserve. The training events included all aspect of filmmaking, including certificates for participants (n = 20). The impact of these training events has been that the Tejon tribe have produced two short films: Returning to Our Roots, a film about the Tejon tribes' return to the lands of the Wind Wolves Preserve and Myth, Heritage, and History. Changes in practices and enabling the Wind Wolves Preserve to implement and deliver their mission statement to educate the public Based upon the Gordian Knot research, a pamphlet and poster has made for the Preserve to use in their education programs and we have developed a website which includes synopses of our analytical work and includes Native American voices. We have installed a VR set-up at the Wind Wolves Preserve as a means to educate the public about their cultural resources and to deflect harmful human visitation to the site by offering a virtual alternative. While we have provided outreach at the Wolves Preserve Spring Festivals each year of the project to engage the public (21,000 people), this VR has been prominent over the last two years where we have had 489 people use the VR. Robinson also have provided bespoked tours for potential donors resulting in contributions to the Preserve. Finally, much of our research has reached the widert public through local and state wide media coverage. Internationally, we have published articles in the iNews (257,000 readership) and in the online press including The Conversation/Smithsonian Magazine) (20,388 reads).
First Year Of Impact 2016
Sector Education,Leisure Activities, including Sports, Recreation and Tourism,Culture, Heritage, Museums and Collections
Impact Types Cultural,Societal,Economic

Title Data for "Datura quids at Pinwheel Cave, California, provide unambiguous confirmation of the ingestion of hallucinogens at a rock art site" 
Description Data set for chromatographic and mass spectral data for publication figures. 
Type Of Material Database/Collection of data 
Year Produced 2020 
Provided To Others? Yes  
URL https://pureportal.strath.ac.uk/en/datasets/6d5b0425-1204-4b4f-b33d-201774c45bbc
Title Datura quids at Pinwheel Cave, California, provide unambiguous confirmation of the ingestion of hallucinogens at a rock art site, imaging data. 
Description Keyence 3D Imaging/ SEM Images Robinson, David Wayne and Cartwright, Caroline and Kotoula, Elena and Randolph-Quinney, Patrick and Ash, Thomas. 
Type Of Material Database/Collection of data 
Year Produced 2020 
Provided To Others? Yes  
Impact Provides data for publication https://www.pnas.org/content/117/49/31026, 
URL https://uclandata.uclan.ac.uk/213/
Title Unravelling the Gordian Knot: Integrating Advanced Portable Technologies into the Analysis of Rock-Art Superimposition 
Description RTI and pXRF data from the project for permanent archiving. 
Type Of Material Database/Collection of data 
Year Produced 2021 
Provided To Others? Yes  
Impact All this data has contributed to a number of publications both completed and in progress as well as for Bedford's PhD. 
URL https://archaeologydataservice.ac.uk/archives/view/1003532/landing.cfm
Description Engagement with Native Americans 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Other audiences
Results and Impact During the course of the project, we have engaged with regional Native American groups such as the Chumash and the Kitanemuk. In particular, we worked closely with the Tejon Indian Tribe. Historical processes of genocide, colonialism, and exclusion have disenfranchised Native Californians from their own ancestral past. Through our archaeological research we moved towards redreesing this intergenerational trauma by directly reconnecting Native communities to their lost ancestral sites and material cultural. We did this through site visits in 2018/19/20, workshops on rock art management, cultural background, language, and story telling. Specifically, we included working closely with the Tejon Tribe co-construction of the Virtual Reality platform which we discussed in one of our publications on VR (also discussed in https://theconversation.com/how-virtual-reality-is-opening-up-some-of-the-worlds-most-inaccessible-archaeological-sites-88286)
Year(s) Of Engagement Activity 2018,2019,2020,2021
URL https://academic.oup.com/iwc/article/31/2/167/5470140?login=true
Description International coverage of project publicatoin 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Our publication 'Datura quids at Pinwheel Cave, California, provide unambiguous confirmation of the ingestion of hallucinogens at a rock art site' received intense media coverage in December of 2020. According to the almetric index (https://www.pnas.org/content/117/49/31026/tab-article-info), 90 international media outlets have covered the findings of this publication. This included coverage by CNN, MSNBC, BBC, The Independent, National Geographic, Forbes, Science, etc. There also has been radio interviews included representatives of the Tejon Indian Tribe such as on the US radio and podcast Bigpicture Sciene http://bigpicturescience.org/segment/sandra-hernandez-david-robinson-datura-discovery. Finally, print magazines have also covered the project such as the French magazine Les Cahiers Science & Vie.
Year(s) Of Engagement Activity 2020,2021
URL https://www.pnas.org/content/117/49/31026/tab-article-info
Description International coverage of virtual reality work 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact International coverage of our virtual reality work includes over 24,000 readers via The Conversation with coverage by The Smithsonian and a two page spread in Inews (with ~250,000 readership).
Year(s) Of Engagement Activity 2018,2019,2020,2021
URL https://theconversation.com/how-virtual-reality-is-opening-up-some-of-the-worlds-most-inaccessible-a...