Ingmar Unkel

The Clock in the Corn Cob: On the Development of a Chronology of the Paracas and Nasca Period Based on Radiocarbon Dating

The people of the Paracas and Nasca cultures, who created the world-famous geoglyphs, lived in the desert of the south coast of Peru approximately between 800 cal BC and 630 cal AD. The archaeological chronology of these cultures thus far was based almost exclusively on a sequence of seriated ceramic styles. The numeric dating of some of the style phases was supported only by few radiocarbon dates. Here we present the first numeric chronology of the Paracas and Nasca culture based on 14C-dating of approximately 120 organic samples from settlement and tomb relics, as well as on material derived from geoglyph sites in the Nasca/Palpa region (South Peru). It is thus far the largest detailed numeric chronology for pre-Columbian times in all of South America. The main focus has been on the Nasca settlement centers near Palpa, Los Molinos, and La Muna, the Paracas site of Jauranga and the Initial period site of Pernil Alto. Most of the 14C-samples have been dated at the AMS facilities at the ETH Zurich (Switzerland) and at the Lund University (Sweden). The targets were produced in the new graphitization line at the Heidelberg 14C-laboratory (Germany), which was designed and developed during the NTG-project.

A Chronology of the Pre-Columbian Paracas and Nasca Cultures in South Peru Based on AMS 14C Dating

The people of the Paracas and Nasca cultures, the creators of the famous geoglyphs, lived in the desert of the southern coast of Peru between about 800 BC and AD 650. The archaeological chronology of these cultures has been based almost exclusively on a sequence of ceramic styles. The absolute dating of some of the style phases was supported by a few radiocarbon dates (Rowe 1967). Here, we present an absolute chronology of the Paracas and Nasca cultures based on 14C dating of more than 100 organic samples from settlement and tomb relics, as well as on material derived from geoglyph sites in the Nasca/Palpa region (south Peru). The main focus has been on Nasca period settlement centers near Palpa, Los Molinos and La Mua, the Paracas period site of Jauranga, and the Initial period site of Pernil Alto. Most of the 14C samples were dated at the accelerator mass spectrometry (AMS) facility of the ETH Zurich (Switzerland). The targets were produced in the newly built graphitization line at the Heidelberg 14C laboratory (Germany). Clay (adobe) bricks, which are quite a common building material in Peru, were successfully tested to be used for AMS 14C dating of adobe architecture in Peruvian archaeology.

The use of hair as an indicator of occupational (14)C contamination.

This paper presents a study in which the specific activity of 14C in hair has been investigated as an easily determined bio-indicator of the integrated 14C exposure (over several months). The study includes 28 Swedish workers handling 14C-labelled compounds, or working in a 14C-enriched environment. Hair samples from personnel at a Swedish nuclear power plant showed very low levels of 14C contamination, if any. In contrast, personnel at the investigated research departments showed 14C levels in hair of up to 60% above the natural specific activity of 14C. Much higher levels, up to 80 times the natural specific activity of 14C, were found in hair from individuals working at a pharmaceutical research laboratory. This contamination was, however, not solely an internal contamination. There were indications that most of the 14C in the hair originated from airborne 14C-compounds, which were adsorbed onto the hair. The difficulties in removing this external 14C contamination prior to analysis are discussed, as are the possibilities of using accelerator mass spectrometry to analyse various types of samples for retrospective dose assessment.

Where to Dig for Fossils: Combining Climate-Envelope, Taphonomy and Discovery Models

Fossils represent invaluable data to reconstruct the past history of life, yet fossil-rich sites are often rare and difficult to find. The traditional fossil-hunting approach focuses on small areas and has not yet taken advantage of modelling techniques commonly used in ecology to account for an organism’s past distributions. We propose a new method to assist finding fossils at continental scales based on modelling the past distribution of species, the geological suitability of fossil preservation and the likelihood of fossil discovery in the field, and apply it to several genera of Australian megafauna that went extinct in the Late Quaternary. Our models predicted higher fossil potentials for independent sites than for randomly selected locations (mean Kolmogorov-Smirnov statistic = 0.66). We demonstrate the utility of accounting for the distribution history of fossil taxa when trying to find the most suitable areas to look for fossils. For some genera, the probability of finding fossils based on simple climate-envelope models was higher than the probability based on models incorporating current conditions associated with fossil preservation and discovery as predictors. However, combining the outputs from climate-envelope, preservation, and discovery models resulted in the most accurate predictions of potential fossil sites at a continental scale. We proposed potential areas to discover new fossils of Diprotodon, Zygomaturus, Protemnodon, Thylacoleo, and Genyornis, and provide guidelines on how to apply our approach to assist fossil hunting in other continents and geological settings.

Climatic influence on Lake Stymphalia during the last 15 000 years

Known from the ancient myth of Heracles fighting the Stymphalian birds, the karst polje of Stymphalia (22°27’E, 37°51’N) is an ideal site to study the climate history of the area. Stymphalia is the only natural perennial lake on the Northern Peloponnesus, which provides a continuous sedimentary record of the entire Holocene and a large part of the Last Glacial. As a large and quite reliable water reservoir, Lake Stymphalia and its surrounding karst springs played an important role for the water supply of the region from ancient time until today. However, due to climate fluctuations, the water supply can change significantly, challenging the water management of the people living in the area. Here we present geochemical analyses of the uppermost part of a lake sediment core (STY-1), recording the changes in climate and water supply during the Holocene and the Late Glacial. The chronology is based on several 14C dates combined to a Bayesian age-depth model. Using XRF elemental analysis, we compare the influx of terrestrial material (indicated by K and Rb) to the carbonate precipitation in the lake (indicated by Ca and Sr). The Rb/Sr ratio as a proxy for changes between dry/warm and wet/cold conditions indicate pronounced wet phases around 6800, 4000–3700–4000, 3500–3000 and 500–200 cal BP.