Discovery, Preservation

1
Discovery, Preservation Dating of
Archaeological Materials

• Arch 2800, Part III

2
Archaeological Discovery

• What we find at archaeology sites depends on.
• how, where, how intensely we sample the
  archaeological record.
• how well materials are preserved in
  archaeological contexts.

3
Survey, Excavation, Recovery

• Survey systematic exploration of large areas to
  locate sites.
• Often done as pedestrian (walking) survey, but
  might employ aerial photographs other methods.
• Excavation systematic exploration of subsurface
  areas (digging at sites) to recovery samples of
  artifacts.
• Recovery systematic sieving of sediments to
  recover artifacts down to a particular small
  size.

4
Excavation screening
5
Aerial Photo of Serpent Mound, Ohio
www.hope-of-israel.org
6
Preservation
7
The Arnold Research Cave Fauna
Preservation of organic remains at Arnold
Research Cave is Excellent recovery technique
was more influential on the sample. M Bone,
Plants C Dry, Enclosed D Buried S Dry,
Loose Silt T Holocene
8
Taphonomy

• Taphonomy answers the question what are these
  bones doing here? (Now)
• How did they get to where archaeologists find
  them?
• the study of processes that influence bones
  after an organism dies to when the archaeologist
  finds them.
• Taphonomy is a bad dog.

9
Taphonomy
Taphos burial Nomos law (Greek) The
science of the laws of embedding or burial. Has
come to mean the study of all processes
influencing bones from their death to their
recovery by researchers or investigators.
Paraphrased from Lyman (1994)
10
Important Considerations

• We work with samples.
• Those samples have taphonomic histories.
• Those samples are not biased.
• Like all samples they have a certain utility.

Photo of fragmented white-tailed deer remains
from the Koster Site, Illinois.
11
Taphonomic Histories Life assemblage live
animal communities Death assemblage available
carcasses Deposited assemblage carcasses or
portions that come to rest at site Fossil
assemblage portions that survive to be
recovered Sample assemblage portions that are
recovered
Time
Paraphrased from Klein and Cruz-Uribe (1984)
12
The Life Assemblage
13
The Death Assemblage, part I
14
The Death Assemblage, part II
15
The Death Assemblage, part III
16
The Deposited Assemblage
The Fossil Assemblage?
17
The Sample Assemblage, part I
18
The Sample Assemblage, part II
19
Preservation

• At times its like building a puzzle with missing
  pieces and no flat surface to work on.
• This is what provides archaeology with its sense
  of intrigue and mystery.
• And, those rare gems that are well preserved must
  be carefully recovered or information is lost.
• There are no opportunities to re-sample.

www.peninsulautism.org
20
Dating
dating-websites.net
www.icq.com/img
images.mojodate.com
www.trustcupid.com/images

• Advice, 10 cents

21
Two Types of Dating

• Absolute assigns a numerical date to a past
  event.
• Relative does not equal dating your sister.
• Assigns order of events as older-than
  younger-than (not how much).

22
Absolute Dating Methods

• Radiometric, half-life techniques
• One half-life is the amount of time it takes for
  half of a radioactive material to decay.
• Radiocarbon dating (HL approx. 5,730 yrs)
• Potassium-Argon dating (HL 1.25 billion yrs)
• Other techniques
• e.g., paleomagnetism, dendrochronology.

23
A Smidgeon of Chemistry
www.calvin.edu

• Isotopes are forms of an element whose nuclei
  have the same atomic number, the number of
  protons in the nucleus, but different mass
  numbers because they contain different numbers of
  neutrons.
• A radionuclide is an atom with an unstable
  nucleus. The radionuclide undergoes radioactive
  decay by emitting gamma rays and/or subatomic
  particles radioactive isotope.
• If we can measure how fast decay occurs, we can
  date stuff.

24
Radiocarbon Dating

• Uses C14, which is radioactive.
• Half-life of approx. 5,730.
• How does one know that one half-life has passed?
• Ratio of C14 to either C13 or C12 (stable).
• Can be used to date organic matter (carbon).
• Only useful back to a maximum of 60,000 years
  ago.

25
Two Important Concepts

• Target Event what you would like to know the age
  of.
• Date Event what you end up obtaining the age of.
• Target Dated Events are not necessarily the
  same thing.

26
(No Transcript)
27
Summary

• Relative dating allows archaeologists to order
  cultural change.
• Absolute dating allows, within limits, the
  assignment of numerical time to evolutionary
  change.