ANT100Y1 Lecture Notes - Radiocarbon Dating, Thermoluminescence Dating, Flaked

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Published on 21 Apr 2013
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Tools and Techniques
- Archaeology usually deals with history prior to writing (5000 years ago)
o Historical archaeology deals with recent history
o Rely on geology and physical geography to find sites of early human occupation
- Locate archaeological sites where there are fossil remains of a hominin, or of a settlement
- Provenience location of an artifact or feature within a site
o Important to see the environment where artifact was found
- Material culture objects that people have and make and are a direct reflection of human culture and behavior
- to understand how a community changed one must look at:
o changes in environment
o population numbers
o religion and culture
- must look at context where material was found
- material culture is also influenced by site formation process environmental and cultural factors that affect how
and where materials are deposited at an archaeological site
o cultural factors include past populations that dump waste in the same area which create a midden a pile
of garbage in a site, which often helps show about population of time
o another factor is whether people lived in a place permanently or nomadic affects quantity and
distribution of materials
o Its difficult to look at all cultural processes that affect formation of a site because of uncertainty whether
material was used every day or for certain occasions, if the materials are native to that location or region, or
because people may only use certain things at certain times of the year
- Easier to look at inorganic materials such as stone, metals, baked clay, because organic material decays quicker
(bone, shell, hair, paper, muscle tissue)
Fossils
- Fossil locales places where fossilized remains of animals are found, but it doesn’t show on life of animal, only
show remains and location
- Fossil impression of an insect or leaf that is now stone, or bone turned to stone, or remains an animal’s skeletal
structure
- Fossilization when an animal dies the organic matter in the body deteriorates
o What remains are the inorganic mineral salts which usually deteriorate as well but rarely when volcanic ash,
limestone, or mineralized groundwater stick to specimen and make them less likely to deteriorate
o Takes 10,000 years
- Chemical analysis of bone can suggest what the animal ate
- Skeletal findings of hominins were subject to long-term environmental processes
- Taphonomy processes that affect an animal’s remains following its death
o look at distribution of bones in an area reflect predation by a carnivore and disturbance by scavengers
Finding sites:
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- there are two methods of finding sites:
1. Surface techniques include field walking and field surveying
a. Clearing of forests, cultivation, and construction reveal material culture
b. Can see from vegetation, erosion, and artificial processes such as plowing
2. Subsurface techniques more efficient, map features beneath the surface
a. Mechanical techniques include shoveling or trenching
i. Shovel shining: shovel is used to scrape off think layers of surface layer
ii. Make test pits to offer a better understanding of site but not as destructive as uncovering all of
it, also provide sample and give ability to date site’s age
iii. If it’s really deep then you take a small sample: provides snapshot of layers
b. Electronic techniques are non-invasive and don’t disturb the site
i. Radar wavers: map subsurface sedimentary layers and buried archaeological features. shows
map of relative locations and depths of features over a large area
ii. Electrical resistivity meters: measure differences in ability of sediments and other materials
beneath the surface to conduct electricity
Excavation
- Datum a fixed permanent reference point within or near the site
o Defines location of all information and specimens collected from the site
o Future investigations can be spatially related to all previous work at the side
- After choosing a datum point, they lay out a grip system that divides site into 1 or 2 meter squares
o Allows for data all data to later be incorporated into a single system at the end of the excavation
- Presence of patterned variations of materials (trends in the way materials are distributed) reflects the nature and
intensity of past human activity: chemicals (phosphorus and nitrogen), charcoal, soil pH levels
o Soil samples indicate past climatic and vegetation conditions preserved wood fragments, carbonized
seeds, preserved plant parts
- Remains of humans include: artifacts (objects made by humans), ecofacts (natural objects used and discarded by
humans, but not modified), and features (non-portable portions of a side)
o Ecofacts include bones, seeds, pollen, pests
o Artifacts include tools, clay pots, stone figurines
Most common artifact from paths are stone stools (lithic)(made 2.5 MYA)
Also ceramics (started being made a 100,000 KYA)
o Features include, fireplaces (hearths), burials, houses, fences, midden or pits that are dug to put garbage
and then covered up
- Association relationships of artifacts with one another is important to understand past life
o E.g. important to see where tools were located near hominin
Dating techniques
Absolute dating
- Absolute dating estimate age of specimen or deposit in years
- Radiocarbon dating method that used the decay of carbon 14 to date organic remains, can date up to 50000 KYA
o After an organism dies it no longer takes in any radioactive carbon and this dating looks at the decay of
carbon 14
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o Carbon 14 has a half life of 5730
Look at how much radiation is emitted every minute per gram
o To make sure dating is accurate they combine radiocarbon and dendrochronology
o Accelerated mass spectrometry radio carbon dating pushes back time to 80 000 MYA and requires less raw
material which will be destroyed during process
- Dendrochronology determine age of wood by growth rings
o Each ring grows every year of its life and each one shows on the climatic conditions during its life
- Potassium-Argon dating and Argon-Argon dating a.k.a Potassium 40 is a radioactive form of potassium that
decays at an established rate and forms argon40 used in K-Ar dating
o Dates samples from 5000 KYA to 3 BYA
o Measures minerals in rocks, not fossils in rocks
o Usually requires prior occurences of high-temperature events e.g. volcanic eruption
o Ar-Ar dating is used with K-Ar dating to estimate same rock sample
With K-Ar, there is the problem because researchers need different rock sample to estimate K and
Argon, and so they use both methods instead of just one
- Fission-Track dating determine age of uranium-rich minerals such as crystal and glass
o Dates minerals in places of fossils
o Need a prior occurrence of high-temperature event
o Can date a larger variety of objects than the K-Ar method
o Can date from 5 to 20 billion year old
o Measure by counting number of paths caused by decay of uranium isotope atoms and then compare with
uranium content of the sample
o Use with K-Ar so they together provide reliable evidence
- Palaeomagnetic dating identifies geomagnetic patterns in rocks, and dates fossils within rocks
o Unlike above methods this one can date in rocks other than igneous (caused by high temperature)
- Uranium Series dating
- Thermoluminescence dating
- Electron Spin Resonance Dating
- Amino Ace Recemization
- Obsidian Hydration
Above methods are written in book
DO WE NEED TO KNOW THEM?
Relative dating
- Relative dating shows age of specimen relative to another specimen
o Based on stratigraphy which is the study of how different layers of sediments and soils, artifacts, and fossils
are laid down
o Law of superposition states that older layers are generally deeper or lower than more recent layers
o Different animals or plants serve as indicators of relative age in different areas of the world
o If a site is disturbed it will not be a good way of determining relative age
o Use three chemical methods to determine age: F-U-N Trio fluorine, uranium, and nitrogen are all found in
water. The older a fossil is the higher its f or u content will b and lower its n content
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Document Summary

Archaeology usually deals with history prior to writing (5000 years ago: historical archaeology deals with recent history, rely on geology and physical geography to find sites of early human occupation. Locate archaeological sites where there are fossil remains of a hominin, or of a settlement. Provenience location of an artifact or feature within a site. Important to see the environment where artifact was found. Material culture objects that people have and make and are a direct reflection of human culture and behavior to understand how a community changed one must look at: changes in environment, population numbers religion and culture. Must look at context where material was found. Easier to look at inorganic materials such as stone, metals, baked clay, because organic material decays quicker (bone, shell, hair, paper, muscle tissue) Fossil locales places where fossilized remains of animals are found, but it doesn"t show on life of animal, only show remains and location.

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