natural or not?

Recognising rock artNatural or not?

I’m sorry, I haven’t a clue!

WeatheringLocation, slope,

exposure, vegetation

etc

Appearance of original carving

Geology and archaeology

Tools andtechniques used,

length of exposure

Original form of carving

Presence of geological features – e.g. vesicles, bedding planes, fissures

Original form of rock surface

CURRENT APPEARANCE

Does it matter?

Did Neolithic and Bronze Age people distinguish between carved and natural marks?

Perhaps unusual natural features had just as much meaning…

But it matters to recorders…

Recording natural features as rock art could potentially:

inflate numbers skew distribution maps deflect resources

I found it so it must be rock art!

Bias noted in volunteers ‘discovering’ their own new rock art…whilst discounting similar examples recorded by other researchers…

Experience helps…or does it? – The more you become familiar with the local geology the better, but the more you see, the more you will realise how difficult it is!

When is a cup-mark not a cup-mark?

Solution hollow? Eroded concretion? Fossil? Molluscs? Bullet ricochet? Historical origin?

Peck marks

Peck marks are evidence of carving but absence of peck marks is not evidence of natural cupules!

Size

Isn’t that important… Cup marks vary from micro-cups to ‘basins’ but

most carved cups are 3-10cm in diameter

Shape

Most cups are circular but ovals do sometimes occur

Need to consider how erosion may have affected the shape

Depth

Dia. usually 2-5 x depth

Very deep or very shallow features are more likely to be natural

Shallow ‘saucers’ may be the result of spalling of the rock surface

Profile 1

Cup Shape

0

5

10

15

20

25

30

0-1.9 2.0-2.9 3.0-3.9 4.0-4.9 5.0-5.9 6.0-6.9 7.0-7.9 8.0-8.9 9.0-9.9 10.0-10.9

11.0-11.9

12.02.9

Cup Index (Dia./Depth)

No

. Cu

ps

In this sample of 111 cups the majority are 4-5 times wider than they are deep.

Profile 2

Occluded surfaces

Water erosion in sloping cups

Carved cups tend towardshemispherical or conical, and are symmetrical.

Non-symmetrical cups orthose with occluded internalsurfaces are more likely to benatural.

Context 1 Need to look around at local geology

Any similar features on other rocks? Are the ‘cups’ aligned along a bedding plane?

Context 2 Is the cup part of a composition?

Are there other, more diagnostic motifs on the panel? Is the cup part of a ‘domino’ or ‘rosette’ pattern?

Context 3 Is the cup mark on a stone

in a prehistoric monument?

Your turn!Using only visual clues…

XNatural erosion

XNatural erosion

Copt Howe – natural ‘cups’ on the panel…

Copt Howe – natural ‘cups’ on the panel…

?Natural erosion?

?Natural erosion + carving?

XNatural erosion

XNatural erosion

XNatural erosion

Chisel marks from quarrying

X

XNatural erosion

XNatural erosion

XNatural erosion

Iron inclusions

X

XNatural erosion

Bullet strike

X

Marine molluscs

X

?

Marine molluscs?

Marine molluscs?

X

Conclusions

Lots of grey areas between natural and artificial marks

Very difficult to determine using only photographs

Need to consider physical form + context (geological and archaeological)

Local experience helps, but self-bias doesn’t!