SOIL TEMPERATURE MONITORING AT LAKE MUNGO
Implications f o r racemisation d a t i n g
W.R. Ambrose
With t h e time r a n g e of r a d i o c a r b o n d a t i n g b e i n g e f f e c t i v e l y l i m i t e d t o
t h e l a s t 30,000 y e a r s t h e p r e s e n c e of o l d e r a r c h a e o l o g i c a l s i t e s i n our
r e g i o n h a s prompted a n i n t e r e s t i n o t h e r l o n g e r r a n g e d a t i n g t e c h n i q u e s ,
i n c l u d i n g non-radiometric systems. Both r a d i o m e t r i c and c h e m i c a l d a t i n g
t e c h n i q u e s r e l y on d e t e r m i n i n g t h e time f u n c t i o n s of system c h a n g e s where
t h e i n i t i a l s t a t e i s e s t i m a t e d from an e x p e r i m e n t a l l y d e t e r m i n e d end s t a t e
(Oeschger 1982:7). The c o r o l l a r y t o t h i s t h e o r e t i c a l b a s i s f o r a l l d a t i n g
systems i s t h a t a c a l c u l a t e d a g e c a n o n l y b e a s a c c u r a t e a s t h e experiment a l l y determined time f u n c t i o n s of t h e system. The r e l a t i v e d i f f i c u l t i e s
of d e t e r m i n i n g t h e t i m e f u n c t i o n s f o r d i f f e r e n t d a t i n g s y s t e m s make t h e
d a t e s d e r i v e d from them of unequal m e r i t . A l l s y s t e m s s h a r e t h e a d d i t i o n a l
problem of chemical c o n t a m i n a t i o n i n samples from f i e l d w e a t h e r i n g o r sample
p r e p a r a t i o n which can i n t r o d u c e e r r o r s beyond t h o s e i n h e r e n t i n t h e c a l c u l a t i o n of time f u n c t i o n s (Chappell 1982). T h i s i s t y p i f i e d by t h e problems
of r a d i o c a r b o n d a t i n g on bone, which a r e w e l l known t o a r c h a e o l o g i s t s
(McPhail 1982: 3 3 6 )
Beyond t h e e r r o r s c o n t r i b u t e d by many s o u r c e s t o r a d i o m e t r i c d a t i n g ,
t h e chemical d a t i n g systems such a s amino a c i d r a c e m i s a t i o n , f l u o r i n e
d i f f u s i o n and o b s i d i a n h y d r a t i o n , s u f f e r t h e g r e a t e r c o m p l i c a t i o n o f b e i n g
dependent f o r t h e i r b a s i c r a t e c o n s t a n t s on e n v i r o n m e n t a l f a c t o r s . I n o t h e r
words, a s w e l l a s i n f l u e n c i n g t h e p r o c e s s e s o f c o n t a m i n a t i o n f o r a l l a r c h a e o l o g i c a l d a t i n g systems, such f a c t o r s a s s o i l c h e m i s t r y and t e m p e r a t u r e a l s o
d e t e r m i n e t h e r a t e c o n s t a n t s f o r chemical d a t i n g s y s t e m s . It i s l i t t l e
wonder t h a t t h e r e l i a b l e i n t e r n a l n u c l e a r c l o c k s of t h e r a d i o m e t r i c d a t i n g
systems g e n e r a l l y produce more r e l i a b l e and a c c e p t a b l e a g e e s t i m a t e s t h a n
t h e e n v i r o n m e n t a l l y s u s c e p t i b l e r e a c t i o n s of t h e c h e m i c a l d a t i n g s y s t e m s .
D e s p i t e t h e d i f f i c u l t i e s , however, t h e r e a r e r e a s o n s f o r p u r s u i n g
chemical d a t i n g methods; a r c h a e o l o g i s t s a r e w e l l aware of t h e v a r i a b l e
r e l i a b i l i t y of any d a t i n g system, t h e r a d i o m e t r i c o n e s i n c l u d e d , s o t h a t
c o r r o b o r a t i v e d a t i n g by a d i f f e r e n t method i s o f t e n s o u g h t . A s w e l l ,
r e c o v e r i n g a sample s u i t a b l e f o r r a d i o m e t r i c a s s a y i s n o t a l w a y s p o s s i b l e ,
o r t h e e x p e c t e d a g e may f a l l o u t s i d e t h e most e f f e c t i v e t i m e r a n g e of t h e
r a d i o m e t r i c system. There i s a l s o t h e a t t r a c t i o n of d a t i n g t h e a r t e f a c t
d i r e c t l y , by chemical means, a g a i n s t i t s i n d i r e c t d a t i n g from o t h e r m a t e r i a l
c o n t a i n e d a t t h e site. T h i s l a t t e r c o n s i d e r a t i o n h a s produced a g r e a t d e a l
.
o f e f f o r t i n d a t i n g o b s i d i a n a r t e f a c t s from C a l i f o r n i a n s o u r c e s , w i t h some
s u c c e s s ( J a c k s o n 1984: 1 7 3 ) . Bone, b e i n g more u n i v e r s a l i n i t s o c c u r r e n c e ,
h a s b e e n t h e o b j e c t of many a t t e m p t s a t chemical d a t i n g , r a n g i n g from simple
n i t r o g e n d e p l e t i o n t o f l u o r i n e accumulation (Cook 1960); work on f l u o r i n e
p r o f i l e s h a s c o n t i n u e d t o t h e p r e s e n t u s i n g advanced n u c l e a r t e c h n i q u e s
(Coote and Holdaway 1982). Probably t h e most c o n t e n t i o u s of t h e r e c e n t
c h e m i c a l d a t i n g schemes i s based on t h e r a c e m i s a t i o n of amino a c i d s i n bone,
s h e l l and wood (Bada e t a l . 1974; Davies and T r e l o a r 1977; M a s t e r s and Bada
1978; P i l l a n s 1982).
Bone r a c e m i s a t i o n d a t i n g h a s been s u b j e c t t o some s c e p t i c i s m and even
h o s t i l i t y due t o t h e c o n t r o v e r s y s u r r o u n d i n g t h e 40,000+ BP d a t e s c a l c u l a t e d
by Bada and Helfman (1975:167) f o r t h e p r e s e n c e of humans i n North America.
The d a t e s h a v e been q u e s t i o n e d on t h e b a s i s of a d o u b t f u l c a l i b r a t i o n of time
f u n c t i o n s , which were reconfirmed by Masters and Bada (1978:128), b u t more
d i r e c t l y r e j e c t e d b e c a u s e t h e y markedly c o n f l i c t w i t h t h e r a d i o m e t r i c a g e s
c a l c u l a t e d from uranium s e r i e s d a t i n g (Bischoff and Rosenbauer 1982).
R a c e m i s a t i o n d a t i n g of bone h a s been r e p o r t e d from Tasmania (Murray e t a l .
1 9 8 0 ) , and h a s been recommended a s p o t e n t i a l l y u s e f u l f o r o t h e r s i t e s such
a s K e i l o r (Davies and T r e l o a r 1977:89), D e v i l s L a i r , Koonalda Cave, Wyrie
Swamp and t h e Papua New Guinea s i t e a t Nombe ( P i l l a n s 1982:233).
Acceptance o r r e j e c t i o n of a r a c e m i s a t i o n d a t e h i n g e s on a c o n s i d e r a t i o n
o f t h e complex c h e m i c a l r e a c t i o n r a t e s of change i n one o r more of t h e 19
amino a c i d s , a s w e l l a s a n e s t i m a t e of s i t e t e m p e r a t u r e , n o t o n l y f o r t h e
t i m e o f a s a m p l e ' s c o l l e c t i o n , b u t e x t r a p o l a t e d back i n time o v e r any minor
o r major c l i m a t i c changes. The i n t e g r a t i o n of long-term s i t e temperature
r e q u i r e s some measurement of t h e s i t e ' s r e c e n t m i c r o c l i m a t e and a demonstrat i o n of i t s r e l a t i o n s h i p t o t h e g e n e r a l r e g i o n a l t e m p e r a t u r e h i s t o r y
( S c h r o e d e r and Bada 1973).
The v e r y h i g h s e n s i t i v i t y of t h e r a c e m i s a t i o n r e a c t i o n r a t e t o temperat u r e c a n c a u s e a major i n a c c u r a c y i n an a g e d e t e r m i n a t i o n u n l e s s an a c c u r a t e
t e m p e r a t u r e h i s t o r y of t h e d a t e d m a t e r i a l i s known. A s a n example Davies
and T r e l o a r (1977:81) c a l c u l a t e t h a t a 1000-year-old bone a t 25OC produces
t e n t i m e s a s much a s p a r t i c a c i d r a c e m i s a t i o n a s a 2000-year-old bone a t
12.5OC.
The d i f f i c u l t y of e x t r a p o l a t i n g t e m p e r a t u r e c o n d i t i o n s back thousands
o f y e a r s from p r e s e n t - d a y m e t e o r o l o g i c a l r e c o r d s , h a s prompted a d i f f e r e n t
a p p r o a c h by most a u t h o r s i n d e t e r m i n i n g t h e r a c e m i s a t i o n r a t e c o n s t a n t s .
The u s u a l p r o c e d u r e i s t o d e t e r m i n e t h e a g e of a s i t e o r sample by r a d i o c a r b o n d a t i n g ; t h e d a t e d s a m p l e ' s d e g r e e of r a c e m i s a t i o n i s t h e n used t o
c a l c u l a t e a r a c e m i s a t i o n r a t e c o n s t a n t f o r o t h e r unknown age samples a t t h e
s i t e . It c a n b e s e e n t h a t a major assumption i s t h a t o t h e r bones i n o t h e r
p a r t s of t h e s i t e have had t h e same t e m p e r a t u r e h i s t o r y . T h i s assumption
f a l l s i f much o l d e r o r younger specimens from t h e same s i t e have had
d i f f e r e n t t e m p e r a t u r e h i s t o r i e s . The assumption a l s o f a l l s i f t h e same a g e
specimens have had d i f f e r e n t t e m p e r a t u r e c o n d i t i o n s a t t h e s i t e , which could
come a b o u t from d i f f e r e n t c o n d i t i o n s of exposure o r b u r i a l . The problem of
e x t r a p o l a t i o n from a d a t e d t o a n undated specimen r e t u r n s t o a q u e s t i o n of
determining a temperature c a l i b r a t i o n .
O b s i d i a n h y d r a t i o n d a t i n g i s s i m i l a r l y s e n s i t i v e t o environmental temp e r a t u r e , and a s w i t h r a c e m i s a t i o n d a t i n g , t h e time f u n c t i o n s of t h e r e a c t i o n
h a v e b e e n d e t e r m i n e d i n two ways; t h e f i r s t based on e x p e r i m e n t a l h y d r a t e d
o b s i d i a n a t e l e v a t e d t e m p e r a t u r e s (Friedman and Long 1976; Michels e t a l .
1983) and a t normal a i r t e m p e r a t u r e s (Ambrose 1976) and t h e second by e x t r a p o l a t i o n from known r a d i o c a r b o n d a t e d specimens.
Whether f o r p r i m a r y d a t i n g u s i n g t h e i n t r i n s i c r e a c t i o n r a t e c o n s t a n t s ,
o r f o r s e c o n d a r y d a t i n g u s i n g e x t r a p o l a t i o n s from known age s t a n d a r d s , t h e
- --
t e m p e r a t u r e regime a t any d a t a b l e s i t e i s o f p r i m a r y i m p o r t a n c e i n c h e m i c a l
d a t i n g methods. Few a u t h o r s have a t t e n d e d t o t h e n e c e s s i t y o f m e a s u r i n g t h e
t e m p e r a t u r e c h a r a c t e r i s t i c s of sites where c h e m i c a l d a t i n g i s a t t e m p t e d .
Some of t h e problems and c o n t r o v e r s y s u r r o u n d i n g p u b l i s h e d bone r a c e m i s a t i o n
o r o b s i d i a n h y d r a t i o n d a t e s c o u l d b e e n l i g h t e n e d by c a r e f u l measurements of
s i t e t e m p e r a t u r e s . The o n l y s y s t e m a t i c long-term work i n t h i s a r e a i s t h a t
of Friedman and Long ( l 9 7 6 ) , Norton and Friedman (1981) and Trembour and
Friedman (1984) who have measured ground t e m p e r a t u r e s t o 2 m d e p t h s u s i n g
t h e Pallmann t e c h n i q u e (Lee 1969). T h i s method r e l i e s on t h e t e m p e r a t u r e
dependence of t h e i n v e r s i o n of o p t i c a l p o l a r i t y of a s o l u t i o n of s u c r o s e i n
converting t o i n v e r t sugar contained i n small g l a s s v i a l s over t i m e .
The
t e c h n i q u e i s complicated by a pH dependence of t h e r e a c t i o n and r e q u i r e s
v e r y c l o s e a t t e n t i o n t o c a l i b r a t i o n and measurement of t h e s u c r o s e s o l u t i o n s ,
which when p r e p a r e d i n v i a l s have t o be h e l d in c o l d s t o r a g e u n t i l t h e y a r e
used i n t h e f i e l d .
I n A u s t r a l i a , r a c e m i s a t i o n d a t i n g by Murray e t a l . (1980) a t B e g i n n e r s
Luck Cave i n Tasmania h a s been c a l i b r a t e d by r e f e r r i n g t o t h e l a t e P l e i s t o cene r a d i o c a r b o n d a t e d bones a t t h e Bass S t r a i t Cave Bay Cave s i t e on H u n t e r
I s l a n d (Bowdler 1984). Cave Bay Cave, n e a r s e a l e v e l d u r i n g t h e Holocene,
would on a v e r a g e b e warmer than Beginners Luck Cave which i s a t 400 m
e l e v a t i o n , 80 km i n l a n d and 2" f u r t h e r s o u t h . The a u t h o r s (Murray e t a l .
1980:150) g i v e a p r e l i m i n a r y e s t i m a t e of t e m p e r a t u r e d i f f e r e n c e w i t h t h e
Beginners Luck s i t e b e i n g 4OC c o o l e r t h a n t h e Cave Bay Cave s i t e . Our
r e c e n t r e s u l t s r e p o r t e d below from e x p e r i m e n t a l work a t Lake Mungo s h o u l d
a s s i s t i n making more a c c u r a t e t e m p e r a t u r e measurements i n c a s e s such a s
Beginners Luck Cave where r a c e m i s a t i o n d a t i n g i s t o b e a p p l i e d .
P i l l a n s (1982:233) i n reviewing t h e p r o s p e c t s f o r r a c e m i s a t i o n d a t i n g
of a r c h a e o l o g i c a l sites i n A u s t r a l i a , c o n c l u d e s t h a t s u i t a b l e s i t e s w i l l b e
v e r y l i m i t e d w i t h t h e most promising b e i n g c a v e s and permanently w a t e r l o g g e d
s i t e s . I n p a r t i c u l a r h e i s v e r y d o u b t f u l t h a t open s i t e s such a s t h o s e i n
t h e W i l l a n d r a Lakes system w i l l b e amenable t o r a c e m i s a t i o n d a t i n g b e c a u s e
of u n c e r t a i n t i e s a b o u t t h e i r t e m p e r a t u r e h i s t o r y .
I t h a s been u s e f u l t h e r e f o r e t o measure t h e s o r t of t e m p e r a t u r e e x t r e m e s t h a t a r e t o b e found i n
t h i s ' w o r s t c a s e ' s i t u a t i o n . T h i s now a l l o w s some e s t i m a t e of t h e e f f i c a c y
of r a c e m i s a t i o n d a t i n g f o r more t h e r m a l l y c o n s t a n t s i t e s e l s e w h e r e by
a p p l y i n g limits t o e r r o r s t h a t may b e due t o t e m p e r a t u r e m i s c a l c u l a t i o n s .
LAKE MUNGO TEMPERATURE RECORDING
I n order t o t e s t a 'worst case' a r e a f o r its p r e s e n t temperature range
an a r r a y of t e m p e r a t u r e m o n i t o r s was e s t a b l i s h e d a t s i x l o c a t i o n s i n t h e
Lake Mungo-Walls of China a r e a . T h i s paper d e s c r i b e s t h e r e s u l t s of two
y e a r s m o n i t o r i n g and r e l a t e s t h i s t o a medium-term m e t e o r o l o g i c a l t e m p e r a t u r e
r e c o r d f o r t h e a r e a . The Lake Mungo a r e a i s a l s o a t t r a c t i v e b e c a u s e o f t h e
a n t i q u i t y of i t s c u l t u r a l m a t e r i a l s and t h e p r e s e n c e o f f a u n a 1 remains which
could b e used f o r d a t i n g t h e o c c u p a t i o n beyond t h e 30,000 y e a r s a l r e a d y
r e p o r t e d by Bowler e t a l . (1970). The p o s s i b i l i t y o f o c c u p a t i o n e x t e n d i n g
beyond t h e normal working range of r a d i o c a r b o n d a t i n g h a s a l r e a d y been a n
i n c e n t i v e f o r t h e a p p l i c a t i o n of a l t e r n a t i v e d a t i n g methods. For i n s t a n c e ,
thermoluminescence d a t i n g h a s been used t o d a t e f i r e p l a c e s t o 38,000 BP
(Shawcross and Kaye 1980:121).
Temperature m o n i t o r i n g a t Mungo h a s a l s o b e e n u s e f u l i n p r o v i d i n g d a t a
on l o c a l m i c r o c l i m a t i c c o n d i t i o n s which a l l o w c o m p a r i s o n s w i t h contemporary
standard meteorological records, a s a f i r s t s t e p i n e x t r a p o l a t i n g over longer
term p e r i o d s of c l i m a t i c change. - T h e method u s e d f o r m e a s u r i n g s u b s u r f a c e
temperature a t Mungo i s based on t h e temperature dependence of t h e water
vapour d i f f u s i o n r a t e i n t o a p l a s t i c c e l l '(Ambrose 1976, 1982; Norton and
Friedman 1981; Trembour and Friedman 1984).
Temperature d i f f e r e n c e s caused by s o i l colour, a s p e c t , drainage and
s o i l t y p e was expected a t Mungo, s o six s i t u a t i o n s were chosen encompassing
a broad range of c o n d i t i o n s , a s follows (Fig.1):
Station I .
Dry l a k e f l o o r anenometer s i t e . A v e r t i c a l p r o f i l e t o 1.5 m
depth with measuring c e l l s a t i n t e r v a l s of 5, 10, 20, 30, 50, 70, 90, 110,
130 and 150 cm.
Figure 1.
Map of t h e southern portion of the Lake Mungo-Walls of
China l u n e t t e . The f i g u r e s show the l o c a t i o n of f i v e
ground s t a t i o n s ( 1 t o 5) and t h e Mungo Homestead
meteorological box (6) where t h e thermal c e l l s were
used
Station 2.
Southern end of Lake Mungo on t h e c o n s o l i d a t e d Walls of China
l u n e t t e c l o s e t o t h e s i t e excavated by Shawcross (Shawcross and Kaye 1980)
through Mungo phase d e p o s i t s with c e l l s t o a depth of 1.5 m a t i n t e r v a l s
of 5, 10, 20, 30, 50, 70, 90, 110, 130 and 150 cm.
Station 3.
Lakeside slope of t h e l u n e t t e 3 km n o r t h e a s t of S t a t i o n 2. On
a r i d g e between eroded g u l l i e s and t h e s i t e of a f i s h h e a r t h i n Zanci phase
d e p o s i t s . Temperature c e l l s t o 1 m depth a t i n t e r v a l s of 5, 10, 20, 40, 60,
80 and 110 cm.
Station 4 .
F o s s i l beach with s h e l l beds a t t h e edge of t h e former l a k e
1.7 km southeast of t h e anenometer S t a t i o n 1. I n powdery dry d e p o s i t s ,
temperature c e l l s t o 1 m depth a t i n t e r v a l s of 5, 10, 20, 50 and 100 cn?.
Station 5 .
Exposure of red Golgol phase d e p o s i t a t t h e b a s e of t h e l u n e t t e
3 km south of t h e Walls of China v i s i t o r s ' parking a r e a . In damp clayey
sand with temperature c e l l s t o 1 m depth a t i n t e r v a l s of 5, 10, 20, 30, 50
and 100 cm.
Station 6 .
Meteorological box, Mungo Homestead.
A t each ground measuring s t a t i o n a 75 mm diameter hand-augered h o l e was
sunk t o t h e required depth. The c e l l s were i n s e r t e d i n a r i g i d 40 mm d i a meter PVC tube and f i x e d a t t h e p r e s e t i n t e r v a l s w i t h a w i r e c r o s s p i e c e ,
and with t h e i n t e r v e n i n g space between c e l l s f i l l e d with s p o i l from t h e
augered hole. The tube wall had 10 mm p e r f o r a t i o n s a t 100 mm i n t e r v a l s o f f s e t on f o u r s i d e s throughout i t s length t o a l l o w f o r f r e e a c c e s s of m o i s t u r e
between t h e surrounding ground and t h e c e l l s . The PVC t u b e w i t h i t s column
of c e l l s was i n s e r t e d i n t o t h e augered h o l e and s p o i l was compacted i n t h e
space around i t t o keep i t i n t i m a t e l y i n c o n t a c t w i t h t h e surrounding s e d i m e n t ~ . The top end of t h e tube was covered with 10-15 mm of s o i l s o t h a t it
was not v i s i b l e a t t h e ground s u r f a c e .
This procedure was repeated a t 6-monthly i n t e r v a l s a t a l l measuring
s t a t i o n s , when a new s e r i e s of c e l l s was exchanged f o r t h e exposed s e t s .
The f o u r periods (25.4.82-25.10.82,
25.10.82-25.4.83,
25.4.83-25.10.83,
25.10.83-25.4.84)
gave a summer and winter exposure over 2 y e a r s .
The
t o t a l of 155 measuring p o i n t s h a s given a p i c t u r e of t h e s e a s o n a l temperature
amplitude a t each s t a t i o n and provided a measure of t h e t o t a l range between
t h e s t a t i o n s . The short-term thermal c h a r a c t e r i s t i c s of h n g o sediments can
now be r e l a t e d t o t h e medium-term meteorological r e c o r d s .
T h e d a i l y o r seasonal temperature v a r i a t i o n s , expressed a s t h e t o t a l
temperature amplitude over a 1 year c y c l e can be c a l c u l a t e d a s a mean a r i t h metic v a l u e i f simple meteorological r e c o r d s are considered. However, t h e
mean a r i t h m e t i c v a l u e i s not t h e a p p r o p r i a t e f i g u r e t o apply t o chemical
r e a c t i o n r a t e d a t i n g systems because t h e i r r e a c t i o n r a t e s a r e e x p o n e n t i a l l y
r e l a t e d t o temperature.
I n order t o r e l a t e t h e f i e l d r e s u l t s t o t h e meteorological r e c o r d s , and
thereby allow longer term p r o j e c t i o n s of temperature h i s t o r y f o r a s i t e , i t
i s necessary t o make t h e exponential and a r i t h m e t i c v a l u e s compatible.
Norton and Friedman (1981:3) have attempted t h i s adjustment by applying t h e
estimated temperature range t o c a l c u l a t e a c o r r e c t i o n , i n o r d e r t o a r r i v e a t
an ' e f f e c t i v e temperature' f o r amino a c i d r a c e m i s a t i o n and o b s i d i a n h y d r a t i o n
dating. Unfortunately i t i s n o t p o s s i b l e t o a s s e s s t h e s u b s o i l range simply
by e x t r a p o l a t i o n from t h e a i r temperature range; s o i l s u r f a c e temperatures
may have a g r e a t e r amplitude of temperature v a r i a t i o n than a i r temperatures,
while a t g r e a t e r depths t h e temperature amplitude may b e l e s s than t h a t of
t h e a i r . Norton and Friedman (1981:3) suggest a s o l u t i o n t o t h e problem of
a s s e s s i n g t h e temperature range c o r r e c t i o n by u s i n g two monitoring systems,
each having different reaction rate constants, but buried at the same
positions for the same period; they suggest using the thermal diffusion cell
described here alongside the sucrose inversion cell for this purpose.
There is an alternative way to arrive more directly at the range and
the 'effective temperature' of the reaction being measured. The experimental
activation energy of the diffusion cell method (Eact = 41.87 kJ/mol) is lower
than the activation energy for aspartic acid racemisation (Eact = 139.6 kJ/
mol) published by Bader and Helfman (1975:165). Therefore in any condition
of variable temperature the nett effect on the reaction rate of racemisation
will be greater than the cell diffusion rate and both will be greater than
that at the arithmetic mean temperature.
The wider the temperature range the greater is the nett reaction product
compared with that at the static mean temperature. This exponential temperature dependence complicates extrapolation from different depths in a site
because of the attenuating effect of depth on diurnal and seasonal temperature changes. It also complicates extrapolation between sites with different
thermal properties caused by moisture content, sediment type, surface and
aspect. Nevertheless the temperature response of the ground surface to the
cyclic annual variation of radiation can be regularly reflected in subsurface
The regular perioditemperatures to a depth of around 14 m (Oke 1978:41).
city of the annual rise and fall in temperature provides the mathematical
basis for evaluating the arithmetic mean and range of the exponential values
derived from the thermal cells. The conversion of the diffusion cell exponential temperature values to arithmetic temperature values, and the calculation of the annual temperature range, can be achieved by using the winter
The derived arithmetic
and summer cell sets (Chappell and Ambrose n.d.).
values are shown in Tables 1 and 2. One additional complication is the
temperature change lag with depth which is not considered in this paper.
Mungo arithmetic mean temperature values (Celsius)
(air T 18.4 + 7.7 1983/84)
Depth
cm
STATIONS
3
PERIOD
82/3 8314
5
10
20
30
40
50
60
70
80
90
100
110
130
150
Values to
Table 1.
+ .1°c
Arithmetic mean temperature values derived from the winter
and summer half year thermal cell records at five Mungo
ground recording stations (April 1982 to April 1984), and
the Homestead meteorological box (April 1983 to April 1984)
Temperature ranges about the arithmetic mean (Celsius).
Hungo 1982-84.
Air temperature range 1983184 18.4 + 7.7
STATIONS
3
2
PERIOD
Depth
8213
cm
8314
8213
8314
5
10
20
30
40
50
60
70
80
90
100
110
9.5
9.1
8.9
8.2
-
7.9
-
-
-
6.3
130
1 50
Values to
Table 2.
8314
+ .lOc
Arithmetic temperature ranges a b o u t t h e mean; d e r i v e d from
t h e w i n t e r and summer h a l f y e a r thermal c e l l r e c o r d a t f i v e
Mungo ground r e c o r d i n g s t a t i o n s ( A p r i l 1982 t o A p r i l 1984)
and t h e Homestead m e t e o r o l o g i c a l box ( A p r i l 1983 t o A p r i l
1984)
The 20 y e a r temperature r e c o r d f o r t h e Mildura m e t e o r o l o g i c a l s t a t i o n ,
when p l o t t e d a s monthly means, shows t h e e x p e c t e d s i n u s o i d a l c u r v e of t h e
form y = sin X w i t h t h e b a s e l i n e being t h e long-term mean of l6 .g0 ( F i g . 2).
For t h e p e r i o d A p r i l 1982 t o A p r i l 1984 t h e Mildura monthly a i r t e m p e r a t u r e
record shows divergences a l t h o u g h t h e 2 y e a r mean (17.1°) i s c l o s e t o t h e
long-term mean (16.g0).
MUNGO RESULTS
The thermal c e l l r e c o r d a t t h e Mungo m e t e o r o l o g i c a l box f o r A p r i l
1983-April 1984 g i v e s a n annual mean a i r t e m p e r a t u r e of 18.4O w i t h a p l u s
and minus range of 7 . 7 ' compared w i t h t h e Mildura m e t e o r o l o g i c a l r e c o r d f o r
tile same p e r i o d of 16.8O f 5 . 0 ° .
The a i r t e m p e r a t u r e d i f f e r e n c e of 1.6' i s
r e l a t i v e l y s m a l l e r than t h e d i f f e r e n c e s between t h e r a n g e of measuring
p o i n t s of t h e f i v e s u b s u r f a c e Mungo measuring s t a t i o n s . Damage t o t h e
1982-3 a i r temperature c e l l c o n f i n e s c o n s i d e r a t i o n of a i r t e m p e r a t u r e t o
s i t e comparisons t o t h e 1983-4 p e r i o d ,
The s u b s u r f a c e r e s u l t s a r e f o r d e p t h s of 5 cm and more, s o i t s h o u l d
be noted t h a t t h e range of temperatures and d i f f e r e n c e s w i l l b e g r e a t e s t
f o r t h e top l a y e r . Even s o temperatures recorded from t h i s l a y e r a r e
s i g n i f i c a n t l y lower than a t t h e s u r f a c e . The t e m p e r a t u r e s a c h i e v e d from
s o l a r r a d i a t i o n a t t h e s u r f a c e c a n b e t e n s of d e g r e e s h i g h e r t h a n temperat u r e s from only 5 cm depth and may reach 70°C (Geiger 1966:158).
Davis
(1984) by u s i n g t h e r e l a t i v e d e g r e e of h y d r a t i o n of s i n g l e e v e n t t e p h r a s
shows t h a t n e a r s u r f a c e temperature i s h i g h e r t h a n t h a t a t g r e a t e r d e p t h
and h i g h e r than t h e average a i r temperature. The Mungo r e s u l t s a r e c o n s i s t e n t with these observations.
1824
-
n20
-
18-
-
-----
S :::
1:
A
-
p
s0 0 S i n curn, pidiced
84
-- - M y a r
Mildun monthly mnps
-2 year Mildun monthly rsmd
-
.. ..
1 y u r M u m man air ~ m p n t u r e
20
1
1
A
M
1
J
1
J
1
A
1
S
1
O
1
N
1
D
1
J
1
.
F
Figure 2.
1
M
1
A
'
M
'
J
low
1m2
'
J
'
A
'
S
1
O
1
N
'
D
1
J
1
F
M
law
1
A
Summer and winter air temperature records for the
Mildura meteorological station plotted against the
theoretical sine curve. Apart from a slight time
lag there is a close approximation to the theoretical
curve of winter and summer temperature changes for the
20 year record
From Table 1, setting out the annual mean temperatures, it can be seen
that there are significant differences between the 1982-3 and 1983-4 years.
For example the dry lake floor anenometer Station 1 has 1.0' to 1.4' temperature differences between the two years whereas Station 5, the red Golgol
sediment, has a narrower range of differences between 0.4' and 0.9'.
There
are consistently higher temperatures at the ground stations than the air
temperatures measured at the meteorological box at the Mungo Homestead.
The air temperature (1983-4 only) of 18.4' can be compared with the lowest
mean ground temperature of 18.6' at Station 1 and the highest mean ground
temperature of 21.3' at Station 5. The higher ground temperatures, from a
minimum above air temperature of 0.2' to a maximum of 2.9' may seem small
although they could effect the calculated age for a date based on a racemisation rate quite significantly Equally important in determining the
reaction rate is the amplitude of the temperature variation about the mean.
The sinusoidal progress of temperature over the summer and winter half years
provided the basis for calculating the amplitude, or range, of temperature
The results
variations at Mungo, for example at Stations 1 and 2 (Fig.3).
are set out in Table 2.
Table 2, giving the temperature ranges of the measuring points, like
the mean values of Table 1, shows the effects of different years, different
locations and different depths below ground surface. The values assume some
importance for reaction rates which are exponentially dependent on temperature, such as acid racemisation in bone collagen or obsidian hydration. For
.
example a range of 210" about a mean of 20° would i n c r e a s e t h e e f f e c t i v e
racemisation r e a c t i o n temperature by around 3.5'.
I f the sample ages a r e
based on t h e lower mean v a l u e of 20° then f o r racemisation d a t i n g t h e
c a l c u l a t e d age w i l l b e around 80% higher than t h e t r u e value. Inspection
of Table 2 shows t h a t even a t 1.5 m depth, S t a t i o n 2 has an annual v a r i a t i o n
of around 6O t o 7 O which would be enough t o give a 30% t o 40% overestimate
of racemisation d a t e . By any standard t h e e r r o r introduced by an i n c o r r e c t
assessment of a sample's temperature regime over time can s e r i o u s l y impair a
f i n a l age c a l c u l a t i o n f o r chemical d a t i n g systems. The approximation t h a t a
1°C temperature e r r o r w i l l produce a 20;2 racemisation age e r r o r needs t o be
k e p t i n mind when considering ages derived from t h i s system.
Station 1 1983184
Station 2 1983184
1
.
. . . . . . . . . .
A
M
J
Figure 3.
J
A
S
O
N
D
J
F
M
/:
1
A
Summer and w i n t e r temperature means and ranges
c a l c u l a t e d a s a s i n e curve f o r t h e 5 cm ( a ) , 50 cm
( b ) and 150 cm (c) l e v e l s a t S t a t i o n 1 (anenometer
s i t e ) , S t a t i o n 2 (Shawcross excavation s i t e ) and
t h e Mungo meteorological box a i r temperature (A)
f o r A p r i l 1983 t o A p r i l 1984. There i s a n o t a b l e
d i f f e r e n c e i n t h e thermal response of these two
s t a t i o n s a t t h e 50 and 150 cm l e v e l s . Temperature
v a l u e s a r e l i s t e d i n Tables 1 and 2
CONCLUSION
By c l o s e l y monitoring t h e ground temperature a t Mungo a present-day
b a s e l i n e s e t of d a t a is a v a i l a b l e f o r e x t r a p o l a t i o n t o o l d e r periods. The
r e l a t i o n s h i p of t h e Mungo a i r temperature t o ground temperature and t o
medium-term meteorological records a t Mildura allows more p r e c i s e calculat i o n s of chemical r e a c t i o n r a t e s f o r d a t i n g purposes. The temperature
r e c o r d r e p o r t e d h e r e should b e within fO.l°C of t r u e temperature a t Mungo.
T h i s would b e e q u i v a l e n t t o an e r r o r of around 2.5% f o r a racemisation d a t e
and s i n c e t h i s i s l e s s than o t h e r p o t e n t i a l measurement e r r o r s i n t h e dating
system i t should be p o s s i b l e t o make some f u r t h e r progress i n i t s use f o r
a r c h a e o l o g i c a l d a t i n g purposes.
ACKNOWLEDGEMENTS
I would l i k e t o thank t h e New South Wales P a r k s and W i l d l i f e S e r v i c e
f o r p r o v i d i n g a c c e s s t o s i t e s a t Mungo, and i n p a r t i c u l a r t o P e t e r Clarke
f o r h i s p r a c t i c a l a s s i s t a n c e and e n d u r i n g h o s p i t a l i t y .
REFERENCES
Ambrose, W.
1976 I n t r i n s i c h y d r a t i o n r a t e d a t e of o b s i d i a n . I n R.E. Taylor
New J e r s e y :
( e d . ) Advances i n obsidian glass s t u d i e s , pp.81-105.
Noyes
Ambrose, W.
1980
M o n i t o r i n g long-term t e m p e r a t u r e and humidity.
ICCM
B u l l e t i n 6:36-42
Ambrose, W. and P. Duerden ( e d s ) 1982 Archaernetry: an Australasian
perspective. Canberra: A u s t r a l i a n N a t i o n a l U n i v e r s i t y , Research
School of P a c i f i c S t u d i e s , Department of P r e h i s t o r y
Bada, J . L . , R.A. S c h r o e d e r and G.F. C a r t e r 1974 New e v i d e n c e f o r t h e
a n t i q u i t y of man i n North America deduced from a s p a r t i c a c i d
Science 184:791-793
racemization.
Bada, J.L. and P.M. Helfman 1975 Amino a c i d r a c e m i z a t i o n d a t i n g of f o s s i l
bones.
world Archaeology 7:160-173
B i s c h o f f , J.L. and R . J . Rosenbauer 1982
Mar Man and Sunnyvale s k e l e t o n s .
Uranium s e r i e s a g e s of t h e Del
Science 217:756
Canberra: A u s t r a l i a n
Bowdler, S.
1984 Hunter H i l l , Hunter Island.
N a t i o n a l U n i v e r s i t y , Research School of P a c i f i c S t u d i e s , Department
of P r e h i s t o r y , Terra Australis 8
Bowler, J . M . ,
R. J o n e s , H . A l l e n and A.G. Thorne 1970 P l e i s t o c e n e human
r e m a i n s from A u s t r a l i a : a l i v i n g s i t e and human c r e m a t i o n from Lake
Mungo, w e s t e r n New South Wales. World Archaeology 2: 39-59
C h a p p e l l , J . 1982 Radiocarbon d a t i n g u n c e r t a i n t i e s and t h e i r e f f e c t s on
s t u d i e s of t h e p a s t . I n Ambrose and Duerden 1982:322-335
C h a p p e l l , J . and W. Ambrose n . d . Ground t e m p e r a t u r e measurement by
diffusion c e l l .
[ I n prep.]
cook, S.F.
1960 D a t i n g p r e h i s t o r i c bone by chemical a n a l y s i s . In R.F.
H e i z e r and S.F. Cook ( e d s ) The application of quantitative methods
i n archaeology, pp.223-245.
Chicago: Quadrangle
C o o t e , G . and S. Holdaway 1982 R a d i a l p r o f i l e s of f l u o r i n e i n archaeol o g i c a l bone and t e e t h : a r e v i e w of r e c e n t developments, In
Ambrose and Duerden 1982:251-261
D a v i e s , W.D. and F.E. T r e l o a r 1977 The a p p l i c a t i o n of r a c e m i s a t i o n d a t i n g
i n a r c h a e o l o g y : a c r i t i c a l review. The Artefact 2:63-94
1984 Tephra h y d r a t i o n r i n d s a s i n d i c a t o r s of a g e and e f f e c t i v e
Davis, J . O .
h y d r a t i o n t e m p e r a t u r e . In R.E. Hughes (ed.) Obsidian studies i n the
Great Basin, pp.91-101.
C o n t r i b u t i o n s t o t h e U n i v e r s i t y of
C a l i f o r n i a A r c h a e o l o g i c a l Research F a c i l i t y No.45
Friedman, I . and W. Long
347-352
1976
Hydration r a t e of o b s i d i a n .
Science 191:
Geiger, R.
1966 The cZimQte near the g r a n d .
University Press
Cambridge, Mass.:
Harvard
1984 O b s i d i a n h y d r a t i o n : a p p l i c a t i o n s i n t h e w e s t e r n Great
Jackson, R.J.
B a s i n . In R.E. Hughes ( e d . ) Obsidian studies i n the Great Basin,
pp. 173-192. C o n t r i b u t i o n s t o t h e U n i v e r s i t y of C a l i f o r n i a Archaeol o g i c a l Research F a c i l i t y No.45
1969 Chemical t e m p e r a t u r e i n g r a t i o n . JoumaZ of Applied
Meteorology 8 :423-430
Masters, P.M. and J.L. Bada 1978 Amino a c i d r a c e m i z a t i o n d a t i n g of bone
and s h e l l . In G.F. C a r t e r ( e d . ) ArchaeoZogicaZ chemistry 11, pp.
Lee, R.
117-138.
Advances i n Chemistry S e r i e s 171
McPhail, S.M.
1982 R e l i a b l e r a d i o c a r b o n d a t e s from b o n e s . I n W. Ambrose
and P. Duerden ( e d s ) Archaeornetry: an Austmzasian perspective, pp.
336-342, Canberra: A u s t r a l i a n N a t i o n a l U n i v e r s i t y , R e s e a r c h School
of P a c i f i c S t u d i e s , Department of P r e h i s t o r y
Michels, J . W . ,
I.S.T. Tsong and G.A. Smith
hydration r a t e s i n obsidian dating.
1983
Experimentally derived
Archaeometry 25:107-117
Murray, P . F . , A . Goede and J.L. Bada 1980 P l e i s t o c e n e human o c c u p a t i o n a t
Beginners Luck cave, F l o r e n t i n e V a l l e y , Tasmania. ArchaeoZogy and
PhysicaZ AnthropoZogy i n Oceania 15:142-152
Norton, D.R. and I. Friedman 1981 Ground t e m p e r a t u r e measurements, P a r t 1
Pallman Technique. US Geologicaz Survey ProfessionaZ Paper 1203 :1- 1 1
Oeschger, H .
1982 The c o n t r i b u t i o n of r a d i o a c t i v e and c h e m i c a l d a t i n g t o
t h e u n d e r s t a n d i n g of t h e environmental system. In L.A. C u r r i e ( e d . )
Nuclear and chemical dating techniques, interpreting the environmental record, pp.5-42. Washington: American Chemical S o c i e t y
Oke, T.R.
1978 Boundary layer cz<mates. London: Methuen
Pillans, B.
1982 Amino a c i d r a c e m i s a t i o n d a t i n g : a r e v i e w . In W. Ambrose
and P. Duerden ( e d s ) Archaeornetry: an Austmkzsian perspective, pp.
228-235. Canberra: A u s t r a l i a n N a t i o n a l U n i v e r s i t y , R e s e a r c h School
of P a c i f i c S t u d i e s , Department of P r e h i s t o r y
Schroeder, R.A. and J . L . Bada 1973 G l a c i a l - p o s t g l a c i a l t e m p e r a t u r e
d i f f e r e n c e deduced from a s p a r t i c a c i d r a c e m i s a t i o n i n f o s s i l bones.
Science 182:479-482
Shawcross, F.W. and M. Kaye 1980 A u s t r a l i a n a r c h a e o l o g y , i m p l i c a t i o n s of
InterdiscipZinary Science
current i n t e r d i s c i p l i n a r y research.
Reviem 5 :1 12- l28
Trembour, F. and I. Friedman 1984 O b s i d i a n h y d r a t i o n d a t i n g and f i e l d s i t e
t e m p e r a t u r e . In R.E. Hughes ( e d . ) Obsidian studies i n the Great
Basin, pp.79-90. C o n t r i b u t i o n s of t h e U n i v e r s i t y of C a l i f o r n i a
A r c h a e o l o g i c a l Research F a c i l i t y No.45
Department of P r e h i s t o r y
R e s e a r c h School of P a c i f i c S t u d i e s
Australian National University
Canberra ACT