Application of tribology in rock art

https://pixabay.com/photos/indian-art-petroglyph-467709/

The quest to find some new interesting topic to write about tribology, ended few days back when I came across an image with a tag “ROCK TRIBOLOGY”. A few clicks here and there on Google to dig deeper about the topic, diverted me to an interesting new application of tribology which even I was unaware of – Rock Art Science. During my research I came across notable work published by Robert G. Bednarik in this regard which is very astonishing and commendable. I have given links in the references for our readers to learn more about his work and findings.

I suppose just like me, most of our readers would be quite unfamiliar with Rock Art Science and believing this I have tried to write this article in lay man terms so that it is understandable to larger group of readers.

Terminology:

Before diving into application of tribology in Rock Art Science we need to be familiar with certain terms:

1. Rock art is ancient or prehistoric drawings, paintings, or carvings on stone made by prehistoric people thousands of years ago in order to communicate with others or depict their lifestyle in their ages to their successors. The human made marking were made by using either additive or reductive processes. The additive process includes rock paintings, pigment drawings, stencils which utilized paints made by single mineral (Black – Charcoal) or by mixing mineral and other ingredient (Yellow and Red pigments – finely ground clay was mixed with a mineral called ochre which is a form of iron). The reductive process includes engravings, percussion petroglyphs which were made by made by the removal of rock material.

tribology in rock art
This Prehistoric rock art shows animals along with some other symbols

2. Cupules are the earliest known prehistoric art produced during all three eras of the Stone Age – Paleolithic, Mesolithic and Neolithic – as well as in historical times. The actual term “cupule” was invented recently by the world-famous archaeologist Robert G. Bednarik, in an attempt to provide a consistent name for a phenomenon which hitherto had been called “pits”, “hollows”, “cups”, “cupels”, “cup stones”, “pitmarks”, “cup marks” – even “pot-holes”. The definition includes three criteria – should be made intentionally, should be made by human and should be symbolistic.

A must see – Drag to 3 minutes and 22 seconds to learn more about cupules

3. Metamorphic rocks arise from the transformation of existing rock to new types of rock, in a process called metamorphism where original rock gets transformed due to exposure to high levels of temperature and pressure. Here metamorphosis means bringing a big physical change.

Marble is a granular metamorphic rock, it is derived from limestone

4. Tribology is the science of wear, friction and lubrication, and encompasses how interacting surfaces and other tribo-elements behave in relative motion in natural and artificial systems.

5. Tribochemistry is the science concerned with the chemical reactions in mineral and synthetic formulations affecting the tribofilm formation on metal surfaces during the boundary lubrication processes.

Research work involving rock art and tribology

Robert G. Bednarik in his paper “Tribology of Cupules” describes a newly observed phenomenon, a rare form of lamina or film protecting petroglyphs from weathering. Kinetic energy metamorphosis (KEM) is a recently discovered tribological process of gradual crystal re-orientation and foliation of component minerals in certain rocks. It is caused by very high, localized application of kinetic energy. The required energy may be provided by prolonged battery of fluvially (meaning: of, relating to, or living in a stream or river) propelled bed load of cobbles, by glacial abrasion, tectonic deformation, and even by tens of thousands of hammerstone blows. It can result in the formation of laminae on specific metamorphic rocks that, while being chemically similar to the protolith, differ significantly in appearance and in their resistance to weathering or deformation. These tectonite layers are of whitish colour and tend to survive granular or mass exfoliation much longer than the surrounding protolith. The tectonite layer’s thickness is a function of impact intensity.

The formation of such laminae within cupules has so far been observed on four types of metamorphic rock:
1. On quartzite at Indragarh Hill, including in Daraki-Chattan Cave, near Bhanpura, India; at Nchwaneng, Korannaberg site complex, South Africa; and at Inca Huasi, Mizque, central Bolivia.
2. On sandstone at Jabal al-Raat, Shuwaymis site complex, northern Saudi Arabia; at Umm Singid and Jebel as-Suqur, Sudan; at Tabrakat, Acacus site complex, Libya; and at Inca Huasi, Mizque, central Bolivia.
3. On silica-rich schist at Condor Mayu 2, Santivañez site complex, Cochabamba, Bolivia.
4. On granite at Wushigou 1, Henan Province, China.

(Colour online) Re-metamorphosed lamina on two cupules at Nchwaneng, South Africa. Source publication: Bednarik, Robert. (2015). The tribology of cupules. Geological Magazine. 152. 1-8. 10.1017/S0016756815000060.

In the research paper “Rock Metamorphosis by Kinetic Energy” Robert G. Bednarik through analytical work confirms the hypothesis of gradual conversion from the metamorphosed cement of the quartzite to tectonite to be identical in the cupules and ancient river channel annealed panels. In both cases three identical stages of tribological transformation can be identified.

First, subtle changes to the grain boundaries and non-siliceous inclusions become evident.

Secondly, as the application of kinetic energy continues, gaps begin to develop between quartz grains and former cement masses as the latter are subjected to crystallization by ductility.

Thrirdly, the anisotropic process is completed, resulting in the conversion of the partially metamorphosed silica to fully crystalline quartz as the molecular re-orientation is completed.

Any further application of force cannot alter the material beyond this state and has limited effect in fracturing the now annealed surface layer.

Large cobbles of the conglomerate immediately overlying bedrock, bearing KEM veneers. Eastern sector of the paleo-channel site at Indragarh Hill near Bhanpura. Source publication: Bednarik, Robert. (2019). Rock Metamorphosis by Kinetic Energy. Emerging Science Journal. 3. 293-302. 10.28991/esj-2019-01192.

In another research paper “The Tribology of Petroglyphs” Robert G. Bednarik states that a better way to measure the rate of rock erosion or weathering would be to perform analysis of surface retreat next to cupule. In the conclusion part of the paper the author states that tribology and tribochemistry need to be involved in the study of any rock art whose production involved interacting surfaces.

References

  1. Prehistoric Rock Art
  2. Bednarik, Robert. (2015). The tribology of cupules. Geological Magazine. 152. 1-8. 10.1017/S0016756815000060. http://dx.doi.org/10.1017/S0016756815000060
  3. Haokip, D.L., 2021. The Petroglyphs of Indo-Myanmar Frontier. Ancient Asia, 12, p.6. DOI: http://doi.org/10.5334/aa.217
  4. Bednarik, Robert. (2019). Rock Metamorphosis by Kinetic Energy. Emerging Science Journal. 3. 293-302. 10.28991/esj-2019-01192. DOI: http://dx.doi.org/10.28991/esj-2019-01192
  5. Bednarik, Robert. (2016). The Tribology of Petroglyphs. 10.2307/j.ctvxrq0ks.15. http://dx.doi.org/10.2307/j.ctvxrq0ks.15
  6. Bhimbetka Petroglyphs
  7. Twyfelfontein – A Survey into the Relationship between Animal-Engravings & Cupules.  

Harshvardhan Singh works as a Senior Service Engineer at a mining firm in India. He is currently working into oil analysis field. Has worked in the filed of tribology and lubrication and loves to write about the same.

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