Table of Contents Table of Contents
Previous Page  8 / 52 Next Page
Information
Show Menu
Previous Page 8 / 52 Next Page
Page Background

6

AramcoWorld

of the chemical

components of the

paint to determine

organic—and thus

datable—ingre-

dients. A method

more recently

applied to cave art,

called uranium-

thorium series

dating, was used

to date that oldest

cave painting,

the red disk in El

Castillo.

But uranium-

thorium doesn’t

directly date the

paint: Instead,

it dates samples

taken from calcite

accretions—where

they are present—

both under and

over paint layers.

The date of the

calcite beneath

the paint provides

a maximum age,

and the date of

the accretions over

the paint give a

minimum age.

Uranium-

thorium series

dating has its

detractors: A

2015 publication

in the journal

Quaternary Inter-

national

by French scientist Georges Sauvet

and collaborators claims much of the natural uranium can

be depleted by leaching, skewing the results. “Application of

the U/Th method for the dating of prehistoric rock art is still

experimental,” they summarize. “Technical improvements and

fundamental research on the causes of error are needed.”

Practitioners of the method respond that taking a suffi-

cient depth of calcite for a sample minimizes this risk. “In

order to control for this, we try to date layers in stratigraphic

order,” says Alistair Pike, a reader in Archaeological Sciences

at the University of Southampton who participated in the El

Castillo dating.

Uranium-thorium is the technique that Maxime Aubert of the

Place, Evolution and Rock Art Heritage Unit at Griffith Univer-

sity in Gold Coast, Australia, employed to date the Sulawesi art.

“In our study, we measured at least three, and up to six, sub-

samples per sample. Their ages are all in chronological order,

confirming the integrity of our samples. If uranium had leached

out, we would have had a reverse age profile—meaning the

ages would have got older toward the surface where they should

be younger,” he explains. Aubert first became involved here in

2012 when colleague Adam Brumm, who was working with

the Indonesian archeologists on the paintings, noticed the calcite

deposits on top of the paintings, and together they invited Aubert

to “come over and have a look.”

Our own adventure starts in Makassar, at the city’s popular

tourist attraction, the

Dutch colonial Fort

Rotterdam, which

houses the Balai Pele-

starian Cagar Budaya

Above:

It was this hand

stencil, in Leang Timpu-

seng, from which uranium-

thorium dating of the

rectangle-shaped sample,

taken from near the little

finger, yielded a minimum

date of 39,900 years.

Mimicking the artists’

method, Pampang lays a

hand on a wall in another

cave,

right:

Of all the

motifs in these caves, the

hand stencils are the most

common. The practice,

asserts world cave-art

specialist David Lewis-

Williams, was not so much

“to make a picture of a

hand (‘I was here’), but

rather to make contact

with the spiritual realm

and its power.”

Maxime Aubert of the

Place, Evolution and

Rock Art Heritage Unit

at Griffith University in

Gold Cost, Australia,

used multiple sub-

samples to ensure the

accuracy of the dating.