ANTH 145 Lecture Notes - Lecture 7: Radiocarbon Dating, Cosmic Ray, Common Era

• School: University of Oregon
• Department: Anthropology
• Course: ANTH 145
• Professor: Fitzpatrick

Document Summary

Anthropology 145 unit 4: how to get a date: A. d. : anno domini (in the year of our lord) Material type: dependent on the method. Age range: also dependent on the method. The closer cultural material is, the more likely it"s related. Things in upper strata are younger than things in lower strata. C12, c13 (both stable) and c14 (unstable or radioactive) Technique based on rate of decay of 14c. 14c formed in upper atmosphere through the effect of cosmic ray neutrons on nitrogen 14. Libby et al. (1948) discovered that decay of 14c occurs at constant rate. Found that after 5568 years, half the 14c in original sample will have decayed (i. e. half-life ) After another 5568 years, half of that remaining material will have decayed, and so on. Especially good for dating: charcoal, shell, bone, coral, textiles, seeds, nuts. Marine samples 400 years older on average. Direct radiocarbon dating of pre-ad 1955 live-collected marine specimens of known historical age;