Dating Flashcards
What is absolute dating? Provide three examples.
uses scientific techniques to date an artifact based on its compositions
- radiocarbon
- thermoluminescence
- dendrochronology
What is relative dating? Provide three examples.
uses an artifact’s location or physical appearance
- stratigraphy
- seriation
- typology
What is another name for radiocarbon dating?
Carbon-14 dating
What requirements must an artifact meet for radiocarbon dating to work?
must be organic
How does radiocarbon dating work? (8)
- C14 produced in upper atmosphere where neutrons and N14 react to produce C14
- C14 is oxidized to create 14CO2, 12CO2, and 13CO2
- CO2 is used by plants for photosynthesis, C isotopes are absorbed, continued along food chain
- therefore, all organic life has both C12 and C14; while alive, ratio is C12:C14
- when living things die, tissue is no longer being replaced, and the radioactive decay of C14 becomes apparent
- in 5,730 years, only half of the C14 will be present
- if we know the ratio of C12:C14 at time of death, and measure the current ratio, we can calculate how much time has passed based on the above half life
- measured ‘before present’
What are four major drawbacks of radiocarbon dating?
- cannot date artifacts older than 55kya
- amount of C14 in the atmosphere varies over time
- extremely low abundance of C14 on earth and therefore in organic matter
- mostly irrelevant for historical archaeology
What is thermoluminescence? Provide two examples.
measures energy emitted after an object has been exposed to temperatures between 400-500 degrees Celsius
- firing of ceramics
- lava
What is optically stimulated luminescence? Provide an example.
- measures energy emitted after an object has been exposed to daylight
- anything buried that was at one point in direct sunlight
What is the most useful form of absolute dating for historical archaeologists?
dendrochronology
What are three drawbacks of dendrochronology?
- not all trees create one ring annually
- climates with little variation in seasons may not produce distinct patterns
- most importantly, even though we can potentially match up until the date the tree was felled, we cannot determine this was the date of its use at any given archaeological site
What are three examples of natural deposition processes?
- alluvial
- colluvial
- aeolian
What are three examples of human deposition processes?
- abandonment
- construction
- farming/gardening
What is the principle of superposition?
newer things will be deposited on top of older things
What is the principle of original horizontality?
assuming that originally, the layers and deposits were deposited in a horizontal way
What is the principle of lateral continuity?
if horizontal layers have been disturbed, that vertical slice does not interrupt horizontality on either side