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Archaeological Sciences

Archaeological Sciences. An Introduction Created By: Margaret Blome U of Arizona IGERT Graduate Student 6/11/07. Archaeology. The study of past cultures through their material remains (Arch 101). Archaeology. The study of past cultures through their material remains (Arch 101)

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Archaeological Sciences

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  1. Archaeological Sciences An Introduction Created By: Margaret Blome U of Arizona IGERT Graduate Student 6/11/07

  2. Archaeology • The study of past cultures through their material remains (Arch 101)

  3. Archaeology • The study of past cultures through their material remains (Arch 101) • Scientific study of material remains of past human life and activities (Encyclopedia Britannica)

  4. Archaeology • The study of past cultures through their material remains (Arch 101) • Scientific study of material remains of past human life and activities (Encyclopedia Britannica) • The recovery and study of material objects, such as graves, buildings, tools, artworks, and human remains, to investigate the structure and behavior of past cultures (Science Dictionary)

  5. Archaeological Sciences • The study of human cultures through the recovery, documentation and analysis of material remains and environmental data including: • architecture, artifacts, biofacts, human remains, and landscapes(Wikipedia) • The use of the hard sciences to understand archaeological questions.(Meg)

  6. Absolute Dating Radiometric 14C Uranium series (U/Th) K-Ar or Ar-Ar Cosmogenic Radionuclides (CRNs) 10Be 26Al 3He Luminescence OSL – Optically Stimulated Luminescence TL – Thermo Luminescence Geoarchaeology: Landscape reconstruction Site formation or destruction processes Catastrophic events Paleoclimatology Reconstructing past climates Soil Sciences Paleobiology Ancient diet and subsistence Ancient DNA Material Science Stone, bone, metal artifacts Archaeological Sciences

  7. Radiometric Dating Vocabulary • Isotopes: forms of a single element (same # protons) with different numbers of neutrons • Parent: the isotope that undergoes nuclear decay • Daughter: the isotope that results from nuclear decay • Parent/Daughter ratio: used in U/Th dating • Radioactive Decay: the process by which an unstable nucleus loses energy by emitting radiation. • Process is random on atomic level, but decay rate is predictable • Half-life: the amount of time it takes for half of an initial quantity of unstable isotopes to decay.

  8. 14C 14N + Energy 40K 40Ar + Energy 234U 230Th + E Radiometric Dating • Radiometric Isotopes (Non-stable) • 14C (Radiocarbon) • U/Th (Uranium series) • K/Ar (Potassium-Argon) 238U 234U + E,

  9. Highlighted are the main elements used in dating Periodic Table of Elements

  10. Essential Information:The isotopes used in archaeology

  11. Why is 14C useful? Production – 14C is created from 14N in the atmosphere due to cosmic ray bombardment Absorption, into all living things Decay – Beginning of the radiocarbon clock at death Problems Production rate varies over time Calibration Required Difference between 14C age on land and in the ocean = Reservoir Effect Can only date objects containing carbon. Trees/wood/charcoal Plants/seeds Bone/hair/teeth Shell/coral Radiocarbon dating: in depth

  12. Carbon 14 production in atmosphere 147N + 10n = 146C + 11p Carbon 14 absorption into living things

  13. 14C Absorption into carbon-based life: Coral – living & ancient/fossil

  14. Plants, Trees & Charcoal

  15. People & Animals!

  16. A – Current amount of 14CA0 – Initial amount of 14C (amount absorbed at time of death)e – Mathematical constant (2.71828…)λ – Constant (ln(2) / half life)t – Time t = 0 Exponential Decay t = 1 t = 2 t = 3 t = 4 t = 5 t = 6 A/A0 = e-λt

  17. Measurement of 14C using AMS (Accelerator Mass Spectrometry) Images from UA physics website Sample pretreatment in UA laboratory

  18. Depends on specific material to be dated Charcoal Plant material Soil All treated with “ABA” process Acid, Base, Acid baths Pretreatment also depends on analytical method to be used AMS measurement needs less than 1 gram of sample Conventional method requires more sample Sample pretreatment methods

  19. Conventional Method Requires more sample Takes a longer time Cheaper! Process: Measures emission of beta particles from sample over time Beta particles are emitted during decay Accelerator Mass Spectrometer (AMS) Requires less sample Faster results! More expensive Process Ionize carbon sample Puts sample into gaseous state Magnets bend flow of sample and separates according to mass and charge Actually sorts and counts isotopes Measurement of 14C

  20. Dating range for U/Th system: Up to 450,000 years Fills the gap between K/Ar and radiocarbon dating Range for 234U/238U: 10,000 – 2 million yrs Why this works? Uranium substitutes for Calcium in calcite Materials that can be dated with this system: Cave deposits Coral CaCO3 (Calcite) Sometimes this includes bone! Uranium series dating: intro

  21. Coral – living & ancient/fossil

  22. How it works: Used in locations with periodic volcanic activity Absolutely date layers of ash that bound stratigraphic layer with archaeological remains Dates from 500,000 to millions of years Modern surface Sterile dirt Ash Artifacts Ash River cobbles K-Ar dating: in depth

  23. K-Ar datable materials • Volcanic ash

  24. Essential Isotope Information:Review

  25. Non radiometric dating methods: • Luminescence – TL and OSL • Can be used on burnt flint and quartz sediment • Cosmogenic Radionuclides (CRNs) • Accumulated amount can be used to date exposed rock surfaces

  26. Quartz Sand Flint tools Bare Rock Sand Dune

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