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Archaeological Dating Methods archaeological dating methods 1. relative dating (aka “older/younger” dating) 2. chronometric dating (aka “absolute” dating) Relative and Chronometric Dating Understanding Humans, 10th Ed., p. 189. REMEMBER: relative methods tell you whether something is older / younger / the same age Understanding Humans, 10th Ed., p. 188. methods REMEMBER: chronometric methods yield a date often scaled in calendar years +/- a number of years (there is a margin of error in every technique) Understanding Humans, 10th Ed., p. 188. Stratigraphy the sequence of geological strata, or layers, formed by materials deposited by water or wind -Law of association -Law of superposition Otero, S. (2004) Social and Behavioural Science Lecture Notes (2014). El Camino College, Torrance, California Main gorge at Olduvai. Note geological beds. Understanding Humans, 10th Ed., p. 197. Note how stratigraphy is used to date stone tools Bed I Olduvai Gorge, Kenya. Hoebel, Anthropology: The Study of Man and Archaeology, 4th Ed., p. 153. archaeological dating methods 1. relative dating 2. chronometric dating (aka “absolute” dating) provides estimates in actual numbers of years (sometimes +/-) Relative and Chronometric Dating Understanding Humans, 10th Ed., p. 189. chronometric dating (aka “absolute” dating) determining the actual age of geological deposits (and the fossils in them) by examining the chemical composition of rock fragments and organic remains containing radioactive substances such as uranium 238, and C 14, which decays at a known rate. It is a destructive method. Direct determination of age determined through laboratory analysis Here are three examples you need to know: C14 dating of organic samples Dendrochronology (tree ring patterns) Molecular clocks (slight genetic markers that change at a known rate) Relative and Chronometric Dating Understanding Humans, 10th Ed., p. 189. Technician in a radiocarbon dating laboratory. Understanding Humans, 10th Ed., p. 194. Radiocarbon dating: Don’t stress out; I will NEVER ask you to explain how it works • Method was developed in the 1940’s by Willard Libby and a team of scientists at the University of Chicago. Very powerful in dating artifacts •and geological events up to about 50,000 years ago. So, if relative dating techniques do not give you a specific age and chronometric dates give you a date range, how do archaeologists choose which dating technique to use?