ATHENS, Ga. - An extensive new field and laboratory study using cutting-edge scientific techniques may make it possible for archaeologists to pinpoint the quarries that supplied stone for some of the most famous statues and architecture of antiquity.
The study by University of Georgia doctoral student Scott Pike was reported today at the 112th annual meeting of the Geological Society of America in Reno, Nevada.
"Statistically, no database will ever be conclusive," said Pike, who is currently an instructor of geology at Oxford College of Emory University. "Yet we are increasingly able to identify even regions within quarries. This analytical approach to marble identification adds new dimensions to the growing field of marble studies."
Pike's work represents the first systematic characterization study of the Pentelic marble quarry region, which is one of the largest and most significant sources of ancient white marble in the eastern Mediterranean. Pentelic marble, originating on Mt. Pentelikon north of Athens, was first used on a large scale, Pike says, for the construction the "Older Parthenon," a structure on the site of the current Parthenon that was destroyed before completion by the Persians in 480 BC.
Building on techniques pioneered by UGA professor of geology emeritus and co-founder of The Association of Marble and Other Stones Used In Antiquity (ASMOSIA) Norman Herz, Pike used the stable isotopic composition and geochemical structure of Pentelic marble samples from known ancient and modern quarries to show that specific origins for some statuary and building marble can be deduced.
Among the most famous statues originating in the Pentelic marble region are the sculptures that originally decorated the Parthenon in Athens - the so-called Elgin Marbles, which were taken from Greece and brought to London in 1806 by Thomas Bruce, the seventh Earl of Elgin. Greece has long demanded the return of the marbles, which are now located in the British Museum.
The study of marble to determine the sources for famous ancient sculptors such as Phidias and Praxiteles has been going on for more than a century. Early on, art historians and archaeologists turned to geologists to discover the origin of the stones because the source was important in understanding everything from political alliances to quarrying techniques to commerce.
"The ability to correctly identify the source regions of marble artifacts assists archaeologists, art historians and museum curators with dating artifacts, piecing together ancient trade routes, giving insight into changing aesthetic values and determining modern forgeries," said Pike.
Mt. Pentelikon has been the primary source of white marble since the early fifth century B. C. The ancient Greeks and Romans used it extensively. Scientists in the 1970s began to measure the stable isotopes of carbon and oxygen as a way to distinguish between marble varieties. A number of scholars have added to the database over the years, but Pike's study is the first systematic characterization of the Pentelikon quarry region.
In his doctoral dissertation for the University of Georgia, Pike points out that stable isotopes are atoms that have the same atomic number (the number of protons in the nucleus) but a different number of neutrons. Calcite is the primary mineral in marble, and since it is composed of carbon, oxygen and calcium, the conditions and manner in which calcite crystallizes affects the isotopic ratio.
"The assumption of marble stable isotope analysis is that each marble region will have undergone a unique geologic history that will be reflected in a distinct set of stable isotope ratios," said Pike.
Other scientists have used similar or very different methods to track marble provenance, with mixed results, said Pike. Some analytical techniques produce such wide variances in their data sets that reliable quarry distinctions can not be made.
For a provenance study to be accurate, Pike says it must include a truly geologically representative reference sample collection. With the cooperation of the Greek Ministry of Culture, Pike was allowed to undertake a thorough topographic and geologic field survey of the entire Pentelic quarry region. Every ancient and modern quarry in the ancient Pentelic quarry region was identified, geologically and topographically mapped and in most quarries multiple fresh marble samples were collected.
"The Greek Ministry of Culture's support of this and similar scholarly projects is evidence of the Greek government's commitment to protect and preserve its rich history," said Pike.
"The current study not only refines the database for the Pentelic quarry region as a whole but also provides signatures for distinct groups of quarries," said Pike. "Our ability to discriminate between quarries within the same quarry field expands the scope of marble provenance studies and allows for more specific archaeological questions to be addressed."
One interesting possibility is that the marble blocks used to construct the Parthenon itself may have come from different and perhaps relatively distant quarries than those from which the Elgin marbles came. Future research and analysis will help unravel that and other mysteries.