GEOARCHAEOLOGICAL APPLICATIONS OF ESR DATING: DETERMINING SITE AGE

Since the 1980’s, electron spin resonance (ESR) has been used for dating a wide variety of materials and sites. Originally, the technique found applications primarily in geology, such as dating sealevel change and fault movements. In recent symposia on ‘trapped charge’ dating methods, however, at least half the presentations have focused on archaeological applications.

Developments in the technique since then allow ESR dating to determine the age for mammalian tooth enamel, corals, foraminifera, barnacles, terrestrial and marine mollusc shells, with 2-5% precision over a time range from 1-5 ka to 3-4 Ma. Since each of these materials can occur in archaeological contexts directly associated with artefacts and hominid remains, sites with Paleolithic material and hominin sites ranging from Australopithecines to Neanderthals and anatomically modern Homo sapiens can easily be dated. ESR ages have been successfully cross-calibrated with many other methods at sites ranging from 5 ka to 2 Ma.

At young sites, such as Mezmaiskaya, Russia, and Obi-Rakhmat, Uzbekistan, ¹⁴C ages sometimes fail to agree well with other dates or with the stratigraphic succession. At both sites, ESR dates resolved the dating problems, demonstrating that the ¹⁴C ages were in error. In Africa, ESR dates showed that the oldest Late Stone Age materials thus far dated occur in the Naisiusiu Beds at Olduvai Gorge, Tanzania. When a Neanderthal tooth was found associated with Middle Pleistocene fauna at Pradayrol, France, ESR was used to assess the age for the hominid by dating associated fauna. At Dakleh and Kharga Oases, Egypt, dating molluscs from lake silts date not only the hominid occupations but periods in which significant wetter climates produced high watertables, and hence, large shallow lakes.