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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!