2:30 PM - 2:45 PM
[HTT16-16] Strontium isoscapes in the Cajamarca region of northern Peru
Keywords:strontium, isoscape, ancient Andes, Peru
In Andean region of south America, Sr isotope (87Sr/86Sr) of human and animal bones have been measured to reveal life styles and migration traits of them. High-resolution Sr isotope map (isoscape) which are basic information to discuss the life style and migrations also have been created in southern Peru and Argentina. In contrast, although bioarchaeological studies including Sr isotope measurement of bones have been performed in the archaeological sites in mountainous region of northern Peru, Sr isotope distribution for isoscapes were not investigated in the regions around the archaeological sites. In this study, we investigated Sr isotope distributions around the archaeological sites in the northern region of Peru, especially in Cajamarca region.
Modern samples for the Sr isoscapes were collected from areas surrounding the Pacopampa, Ingatambo, and Kuntur Wasi archaeological sites in Cajamarca region of northern Peru. A total of 81 samples of modern river water and 153 samples of biological samples (legumes and snail shells), were collected in 2022 and 2023, and their Sr isotope ratios were measured. Sr isoscapes were created based on the measured values using interpolation models, Ordinary Kriging and Empirical Bayesian Kriging. The optimal model was selected. We examined which types of samples were most suitable for archaeological application by comparing the isoscapes for water and biological samples.
As a result of comparing isoscapes created using different models, the predicted values from the Empirical Bayesians Kriging model showed a better fit with the measured values. When we compared the types of samples, the isoscapes of both water and biological samples were roughly consistent with the surrounding geology, but the water and biological isoscapes were not entirely consistent with each other. This suggests that the 87Sr/86Sr distribution of bioavailable Sr differ from those in river water, and may be influenced by local physico-chemical and biological processes. The challenge is to create a model that will be suitable for archaeological discussion in the future.
Modern samples for the Sr isoscapes were collected from areas surrounding the Pacopampa, Ingatambo, and Kuntur Wasi archaeological sites in Cajamarca region of northern Peru. A total of 81 samples of modern river water and 153 samples of biological samples (legumes and snail shells), were collected in 2022 and 2023, and their Sr isotope ratios were measured. Sr isoscapes were created based on the measured values using interpolation models, Ordinary Kriging and Empirical Bayesian Kriging. The optimal model was selected. We examined which types of samples were most suitable for archaeological application by comparing the isoscapes for water and biological samples.
As a result of comparing isoscapes created using different models, the predicted values from the Empirical Bayesians Kriging model showed a better fit with the measured values. When we compared the types of samples, the isoscapes of both water and biological samples were roughly consistent with the surrounding geology, but the water and biological isoscapes were not entirely consistent with each other. This suggests that the 87Sr/86Sr distribution of bioavailable Sr differ from those in river water, and may be influenced by local physico-chemical and biological processes. The challenge is to create a model that will be suitable for archaeological discussion in the future.