Application of Optical Dating to Fossil and Tool-Bearing Cave Sediments at Atapuerca, Spain

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With National Science Foundation support Dr. Glen Burger will conduct two seasons of field research in the Atapuerca region, located 14 km East of Brugos, Spain. An abandoned railway trench cuts through a series of caves which hold extremely important hominid materials and the goal of this research is to date them accurately. Although anthropologists know that hominids evolved in Africa and left this continent as early as 1.8 million years ago, until recently the earliest securely dated materials in Europe dated to less than a half million years in age. It appeared that hominids entered this region only relatively late in their evolutionary history. In this context, a series of recently excavated sites in the Atapuerca region are particularly important because they contain an abundance of hominid skeletal material as well as stone tools and associated faunal remains. Based on paleomagnetic evidence it is clear that the oldest of these occurrences exceed 780,000 years in age. Dr. Berger will analyze the sediments from two sites using IR-OSL to determine the relative - and hopefully the absolute - ages of levels from two of these sites. Pleistocene age sediments older than 40,000 years - the effective range of radiocarbon - and not associated with volcanic materials are extremely difficult to date. The experimental techniques currently employed often do not yield consistent information. Dr. Berger is working to develop an optically stimulated thermolumenescent technique which can be applied to feldspar rather than more commonly studied quartz crystals. Thermolumenescence dating measures time dependent radiation induced damage which accumulates in crystals. Sunlight, it is believed, wipes the slate clean and sets the clock to zero. Thus in dating sediment, one in fact determines not the age of the particles themselves but rather the last time they were exposed to the sun. In archaeological situations where sediments associated with bones and cultural material are buried under successive layers of dirt, last exposure to the sun is useful information. The problem however is that sunlight may not always set the clock to zero and Dr. Berger, in addition to collecting buried materials from the Atapuerca sites, will initiate a broader program of geological survey. He will collect exposed sediments identical to those buried in the sites and use these as controls. This research will not only provide age estimates for important hominid and associated cultural remains. It will also further development of the thermolumenescent dating technique which is potentially applicable in many anthropological, geological and paleontological contexts.