Chapter 4: Dating Methods & Chronology

Question 1

Relative Dating

Answer 1

• chronological sequence without recourse to a fixed time scale
• no actual dates are assigned
• seriation
• stratification

Question 2

Seriation

Answer 2

• chronological ordering of a group of artifacts or assemblages where the most similar are placed adjacent to each other in the series
• involves creating a typology of artifacts and placing them in a relative chronology
• must be using same kind of object (ex. pots)
• columns: different types
• rows: proportion (percent) of each type at a site
• when organized chronologically they will have a “battleship” shape

Question 3

Stratigraphy

Answer 3

• in a succession of layers the bottom layer is the earliest and the top layer the latest
• law of superposition
• principle of association

Question 4

Law of Superposition

Answer 4

in a series of layers in the earth, the one at the bottom was deposited first and those above were deposited sequentially from oldest to youngest

Question 5

Principle of Association

Answer 5

two objects found in the same deposit/layer were deposited at the same time

Question 6

Chronometric Dating

Answer 6

• aka absolute dating
• an estimate of the age
• always include an error (±) or a range
• based on natural processes occurring all the time
• radioactive decay
• accumulation of trapped electrons

ex. radio carbon, thermoluminescence, argon-argon, uranium series

Question 7

Methods Based on Radioactive Decay

Answer 7

• elements have multiple forms (isotopes), including some that are unstable (radioactive)
• half-life

Question 8

Half-life

Answer 8

dating methods based on the principle when a radioactive isotope (R.I.) decays

ex. radiocarbon (R.I. = C-14, half life = 5,730 years)

Question 9

Radioactive Decay Calculations

Answer 9

• the amount of an isotope that has accumulated or that remains in a material
• known half life
• age determined is a statistical estimate

ex. 500 bp ± 50
* means: 68.2% chance that the date is between 550 bp and 450 bp
* double the error: 95.4% chance that the date is between 600 and 400 bp

Question 10

Luminescence Methods

Answer 10

• electrons from radioactive decay in the environment
• trapped in flaws in crystal of some minerals (quartz, feldspar, carbonates)
• accumulate in the traps over time
• determine the ‘dose rate’ using a dosimeter that is place in the sediment for a known duration
• measure the amount of electrons and compare with dose rate to determine the amount of time elapsed

Question 11

Thermoluminescence (TL)

Answer 11

• pottery, burned flint
• “stopwatch” zeroed by heating (pots, heated rock)

Question 12

Optically Stimulated Luminescence (OSL)

Answer 12

• wind deposited sediment
• “stopwatch” is zeroed by light (sediment)

Question 13

Electron Spin Resonance (ESR)

Answer 13

• teeth
• “stopwatch” is zeroed by formation of the crystal (teeth)

Question 14

Absolute Dating

Answer 14

• actual date in solar years previous to the present
• dendrochronology
• varves
• historical chronology

Question 15

Dendrochronology

Answer 15

study of tree-ring patterns

Question 16

Varves

Answer 16

fine layers of washed up sediment deposited in glacial lakes

Question 17

Historical Chronology

Answer 17

• documents with dates (maps, letters, treaties)
• objects with known dates (coins, nails)