V isual A ssessm en t
The highly w eathered condition of m any p ain tin g s an d engravings th ro u g h o u t th e c o n tin e n t h a s led som e re se a rc h e rs to believe th e m to be q u ite an c ien t; often m a n y th o u s a n d s of y e a rs are c la im e d or in fe rre d (eg C h a lo u p k a 1984; T re zise 1971). However, consideration of physical condition alone is of little u se in an y a tte m p t even roughly to estim ate th e ab so lu te age of rock art.
For exam ple, claim s for g reat an tiq u ity have often been m ade for pecked engravings, p artic u larly th e so-called 'P an aram ittee' style (eg: E dw ards 1971: 359-64; M aynard 1979: 84, 93-95). However, a t two sites in C entral A ustralia, th e condition of E u ro p ean n am es engraved over fifty y e a rs ago is now id en tical in a p p e a ra n c e to 'P a n a ra m itte e style' pecked engravings n e a rb y w hich give th e u s u a l im p ressio n of g reat age (R. K im ber p ers. com m.; see also M cC arthy 1967b: 32 for a sim ilar o b serv atio n in th e Sydney- H aw kesbury area).
D irect D ating
In h e r co m p re h en siv e su m m a ry of ro ck a r t c o n se rv a tio n in A ustralia, Rosenfeld sta te s th at:
T he d a tin g of ro ck a r t re m a in s a very d ifficu lt p rocess. No chronological te sts are know n w hich can be ap p lied to th e p ig m e n ts or to th e p a tin a on engravings. (Rosenfeld 1985: 11)
S ince th o se w ords w ere w ritte n sig n ifican t d evelopm ents have occurred. U ntil recently rad io -carb o n te s ts to d eterm ine th e age of an y organic com ponent in pigm ent a r t entailed m ajor dam age to or to ta l d e s tru c tio n of th e p a in tin g . In th e only re p o rte d a tte m p t I have discovered, the date o b ta in ed for a n A m erican In d ia n ro c k p a in tin g w as 'from 100 to 2 0 0 0 y e a rs ', a n
u n a c c e p ta b le m argin of e rro r (G rant 1965: 93, cited in B randi 1973: 171).
D evelopm ents in th e u se of A ccelerator M ass S pectrom etry now en a b le d a tin g of organic co m p o n e n ts in m in u te a m o u n ts of pigm ent or o th er m aterials, an d th is technique h a s recently been tried in A ustralia. Sam ples from a h a n d stencil a t J u d d s Cavern in T asm a n ia re tu rn e d a date of ab o u t 10,000 BP, an d sam ples from 'fra g m e n ta ry p a n e ls of w ea th ered d a rk red pigm ent' a t L aurie C reek, in th e N o rth e rn T erritory, h av e b e e n d a te d to a b o u t 2 0 ,0 0 0 BP (Loy et al 1990).
While th e re s u lts achieved are extrem ely encouraging, d atin g of rock p ain tin g s w ith th is technique is still in its infancy. Obviously, th is m ethod can only be u se d if th ere is an organic com ponent in th e pigm ent, an d even w hen organic com pounds ca n be detected it m ay be difficult to d eterm in e w h e th e r th ey w ere p a rt of the original pigm ent, derived from o th e r so u rce s, or co n ta m in a te d w ith yo u n g er m aterial. The tech n iq u e will require fu rth e r testin g • before w idespread sam pling is u n d e rta k e n .
Rock engravings, by th e extractive n a tu re of th e te ch n iq u e , do n o t in c o rp o ra te a n organic co m p o n en t in th e p ro cess of th e ir execution, an d are therefore n ot am enable to direct dating. There is, however, a variety of m eth o d s for in d irect d atin g of b o th rock engravings an d paintings.
In d ir e c t D a tin g
In th e ab sen ce of conclusive direct dating, re se a rc h e rs m u s t rely on in d ire c t d a tin g , a n d th is is p o ssib le only in fav o u red c irc u m s ta n c e s . In ra re in s ta n c e s , m in e ra l co a tin g s th a t have a c c u m u la te d on th e su rfa c e of rock a r t have th e p o te n tia l for ra d io -c a rb o n or o th e r form s of dating. For exam ple, D ragovich (1986) re p o rts a d ate of a b o u t 10,000 BP for calcium carb o n ate w hich covers a p a tin a te d 'P a n aram itte e style' engraving a t S tu rts M eadow s in S o u th A u stralia, a n d W atch m an is in v estig atin g a variety of m in eral sk in s th a t cover p a in tin g s a n d engravings in various p a rts of the co n tin en t (Alan W atchm an, pers. comm.).
M ore re ce n tly , N obbs a n d D orn (1988) have m e a s u re d the '...ra d io -c a rb o n c o n te n t a n d ch an g es in th e catio n -ratio (CR) of (c a lc iu m + p o ta ssiu m )/tita n iu m ' in th e 'ro ck v a rn is h ’ on pecked m otifs from the Olary region of S o u th A ustralia. They claim th a t th e o ld e st of th e se engravings are 3 1 ,6 0 0 y ears old. A lthough som e re se a rc h e rs seem willing to accep t th e ca tio n -ratio dating te c h n iq u e m ore or less as it s ta n d s (eg Clegg 1988: 139-141; D ragovich 1988: 141), o th e rs advise c a u tio n (eg R en eau an d H a rrin g to n 1988: 141-142; C larke 1989: 6 3 -6 5 ; W a tc h m a n 1989a: 6 5-66 an d 1989b: 246-247). This is a new technique and fu rth e r te stin g is advisable before its reliability can be accepted. T he d isco v ery of ro ck a r t b u rie d in d a ta b le a rch a eo lo g ical
d e p o s its pro v id es a n o th e r m e a n s of in d ire c t d atin g , a n d is ex trem ely v a lu a b le in providing a m in im u m age for a r t (see Rosenfeld et a l 1981; L orblanchet 1983; W endt 1976; D eakin e t
al 1976). U nfortunately, su c h discoveries are a rare occurrence. In A u stra lia , p a in tin g s have n o t b e e n recovered from d ata b le d ep o sits. However, a t D am pier in W e ste rn A u stra lia engraved ro ck s have b ee n found covered by sh ell m idden deposit a b o u t 3,8 0 0 y e a rs old (Lorblanchet 1983: 182) an d a radio -carb o n date of a b o u t BP 13,000 y e a rs h a s b e e n o b ta in e d for o cc u p atio n d e p o sits covering a p a n e l of pecked en g rav in g s in s o u th -e a s t Cape York (Rosenfeld e t al 1981: 33).
The d a te s obtained by Rosenfeld et a l a n d by D ragovich (1986), m ay be se en to su p p o rt th e view th a t som e pecked engravings belong to a very early tradition, b u t extrapolation of su c h dates to sites elsew here is problem atic.
At p r e s e n t th e m o st com m on form of in d ire c t d a tin g is th e c o rre la tio n of s u b je c t m a tte r in th e a r t w ith h is to ric a l, archaeological, ethnographic, ecological or geom orphological d a ta (eg see B ra n d i 1973: 2; C raw ford 1968: 74-80, 89-90; Lewis 198 8 a; C h a lo u p k a 1984: 15; L o rb la n c h e t 1983). In som e in sta n c e s th is m ethod m ay allow ab so lu te dating; m ore often it is only possible to place th e a r t w ithin a b ro a d tim e period, or to provide a m inim um or a m axim um age. In an y case, th is type of d atin g d ep en d s u p o n sufficient detail being p re se n t in th e a r t for
reliable identifications to be m ade. In m any a re a s the a r t is too generalised for th is to be done.