Georadar reveals the unknown parts of the Sierra de Atapuerca caves

Georadar reveals the unknown parts of the Sierra de Atapuerca caves

The CENIEH has participated in a study led by Lucía Bermejo, in which this geophysical method was used to define the bottom part of the caves in the Trinchera del Ferrocarril sites
georadar Sierra de Atapuerca
GPR in Trinchera del Ferrocarril (Atapuerca). Credits: Miguel Ángel Martín

An international team of researchers from the Centro Nacional de Investigación sobre la Evolución Humana (CENIEH) and the University of Denver has managed to define the bottom part of the caves in the Trinchera del Ferrocarril sites (Cueva Peluda, Sima del Elefante, Galería and Gran Dolina), using georadar, revealing the unknown parts of these caves in the Sierra de Atapuerca (Burgos, Spain).

This non-invasive geophysical method, also known as ground penetrating radar (GPR), widely employed in archaeology because it is rapid and easy to apply, enables structures buried at different depths to be discovered. However, using it to study caves is usually discarded because the clayey sediments that fill them, being highly conductive, attenuate the radar signal, thus limiting its penetration capacity.

“Nevertheless, in our case this characteristic has served for studying the lower part of these caves, because we have been able to clearly distinguish the walls from the conduits, and from the sediments that fill them”, states Bermejo, lead author of this study, which was published recently in the journal Geomorphology.

It was possible to constrain the caves' depth by drilling two mechanical boreholes with core recovery, which have identified up to 17 meters of terrigenous fillings, such as in the case of the Galería site. Moreover, different types of sediments were discernible, thanks to which a possible conduit full of fluvial sediments was recorded, which would connect the lower level of Cueva Peluda with the lower part of Sima del Elefante.

Trinchera del Ferrocarril caves (Atapuerca). Credits: L. Bermejo et al

Quarrying activity

On the other hand, the information provided by the georadar and historical photographs have made it possible to establish how far the impact of the quarrying activity that took place at the Trinchera until the 1970s extended.

This activity was especially intensive between Cueva del Compresor, situated opposite the Galería site, and Gran Dolina, and it produced rubble fills up to 4 meters thick in the areas most impacted.

“All these data will help to optimize strategies for future excavations, as in this study it has been possible to identify the best preserved zones”, concludes Bermejo.

Full bibliographic information

Bermejo, L., Ortega, A. I., Parés, J. M., Campaña, I., Bermúdez de Castro, J. M., Carbonell, E., & Conyers, L. B. (2020). Karst features interpretation using ground-penetrating radar: A case study from the Sierra de Atapuerca, Spain. Geomorphology (0), 107311. doi: 10.1016/j.geomorph.2020.107311
Press release from CENIEH

Subsurface imaging technology ground penetrating radar Australia Victoria graves

Lost graves identified by new archaeology methods

Lost graves identified by new archaeology methods

Archaeologists are using subsurface imaging technology to help community groups map unmarked graves

Subsurface imaging technology helps find lost graves in Australia. Credit: Flinders University

"This is a huge issue, particularly for rural communities," says Dr Ian Moffat, Senior Research Fellow in Archaeological Sciences at Flinders University.

"Using geophysics provides a non-invasive and culturally appropriate way to map unmarked grave sites."

Dr Moffat leads a group which recently published the results of using Ground Penetrating Radar (GPR) and GPS surveys to non-invasively map the location of unmarked graves within the Lake Condah Mission Cemetery in Victoria, a state in Australia.

Established in 1869, this cemetery remains an important site for the Gunditjmara community, because while it has only 26 marked graves, it is anecdotally thought to contain more than 100 graves.

The GPR survey identified an additional 14 probable unmarked graves as well as 49 other areas that may contain one or more unmarked burials.

"The great leap forward with this particular study was the close partnership between the Gunditj Mirring Traditional Owners Corporation and the researchers to achieve such a positive outcome," says Dr Moffat.

"Many Australian Indigenous communities are anxious not to disturb graves, so this survey provides useful information to assist the Gunditj Mirring Traditional Owners Corporation in planning future burials within this cemetery by identifying large areas which are free of graves."

Damein Bell, CEO of Gunditj Mirring says, "Our Elders informed the researchers of their knowledge of where the known graves were and our community now have marked the unknown gravesites of our ancestors".

GPR is a geophysical technique that uses high frequency electromagnetic waves to image the subsurface, making it ideal for mapping changes in lithology or soil structure.

Extensive subsurface disturbance present at the Lake Condah Mission Cemetery and the presence of many tree roots made the effective interpretation of GPR data difficult, but it was still possible to delineate areas where no unmarked graves are present.

"This is an important outcome for managing the cultural heritage of the cemetery because it identifies areas where new graves can be emplaced in a culturally appropriate fashion," says Dr Moffat.

"This demonstrates the utility of GPR as a means of effectively managing heritage sites containing unmarked graves, even when substantial subsurface disturbance is present."

Dr Moffat believes the technique of using GPR and GPS readings will now have a much wider application across pioneer and heritage sites throughout Australia and will be undertaking surveys of other cemeteries at Lake Wangary, Berri and Kingscote over coming weeks.

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The research paper - "Ground penetrating radar investigations at the Lake Condah Mission Cemetery: locating unmarked graves in areas with extensive subsurface disturbance," by Ian Moffat, Julia Garnaut, Celeste Jordan, Anthea Vella, Marian Bailey and Gunditj Mirring Traditional Owners Corporation - has been published by the Journal of the Archaeological and Anthropological Society of Victoria.

Subsurface imaging technology ground penetrating radar Australia Victoria graves
Dr. Ian Moffat, Senior Research Fellow in archaeological sciences at Flinders University, will map the Kingscote pioneer cemetery in May. Credit: Flinders University

Press release from Flinders University