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1. Topic:
Surface Exposure Dating,
methods
and
applications
by
MuhammadHaseebDurrani
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2. Content
 Define surface exposure dating
 Example
 Methods
I. Absolute
II. Relative
 Explanation of some methods
 Applications
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3. Surface exposure dating:
It is collection of geochronological techniques for estimating the length
of time that a rock has been exposed or near earth’s surface.
 It is used to date geological events such as:
o Glacial advances
o Erosion history
o Lava flows
o Meteorite impacts
o Rocks sides
o Faults scraps
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4. Example
Cosmogenic radionuclide dating:
 Cosmogenic nuclides are created through the collision of cosmic rays with atomic
nuclei.
 These nuclei can be atmospheric (N,O) or terrestrial relies on terrestrially.
 Surface exposer dating formed nuclide and soil dating relies on atmospherically from
nuclides.
 Basic principal is that these radio nuclide are produce at known rate through this
scientist can date how long a particular surface has been exposed, how long a certain
piece of material has been buried or how quickly a location is eroding.
 The excess relative to natural abundance of cosmogenic nuclide in rock sample is
usually measured by means of accelerator mass spectrometry.
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5. • Methodsofsurfaceexposuredating
Basically there are two Major methods
Absolute Dating
And
Relative Dating
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6. • Relativevs absolutedating
o Absolute Dating
• it gives accurate dating of any material.
o Relative dating
• determining the relative order of past
events (i.e., the age of an object in
comparison to another), without
necessarily determining their absolute age.
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7. • AbsoluteDating
It is further divided into following
 Amino acid racemisation
 Archaeomagnetic dating
 Dendrochronology
 Ice core
 Incremental dating
 Lichenometry
 Paleomagnetism
 Radiometric dating
 Radiocarbon
 Uranium-lead
 Potassium-argon
 Tephrochronology
 Luminescence dating
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8. • RelativeDating
It is further divided into following
 Fluorine absorption
 Obsidian hydration
 Seriation
 Stratigraphy
 There are many methods of Dating. We will discuss few of them.
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9. Absolute Dating By:
DEF
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10. • Absolute dating
 It is the process of determining the age on a specified time scale in geology and
archaeology i.e. it gives accurate dating of any material.
 It is based upon physical, chemical, & life properties of the materials, materials of
the artefacts, buildings etc.
 Techniques include tree rings in timber, radiocarbon dating of wood or bones &
trapped charge dating i.e. thermoluminescence dating.
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11. • Radio metric dating
 The process of determining the age of rock from the decay of their radioactive
elements.
 There are over forty such techniques, each using a different way of measuring them.
 It is accurate because there is complete agreement between radiometric dates and
other dating methods.
The radio active methods we are discussing are:
1. Radio carbonation
2. K-Ar Dating
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12. • Radiocarbon Dating
 One of the most widely used & well known dating technique.
 Based on radioactive decay of C-14.
 Half life of C-14 is 5730 years.
 Plants take C-14 from CO2 and this C-14 circulates in food chain.
 With death, the uptake of C-14 stops.
 By measuring C-14 in organic material, scientists can determine the date of death of
that organism.
• Limitations
 C-14 as a very short half life of about 5730 years.
 Due to this short life it is reliable only up to 75,000 years.
 Thus it is not highly effective.
 Still highly effective when calibrated with other techniques like tree ring dating.
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14. • Potassium- Argon Dating
 Potassium-40 is a radioactive isotope of potassium that decays to argon-40.
 Half life of K-40 is 1.3 billion years.
 Potassium is common in rocks and minerals.
 The date measured reveals the last time the object was heated past the closure
temperature at which Argon can escape.
 The graph shows the age K-Ar method and other methods can find.
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15. • Luminescence Dating
 It is the type of dating methodology that measures the amount of light emitted
from energy stored in certain rock types and derived soils to obtain an absolute
date for specific event that occurred in past.
 Luminescence dating may be:
1. Thermoluminescence dating
2. Optically stimulated luminescence (OSL) dating
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16. • Thermoluminescence dating
 It dates items to the last time they were heated.
 Based on the principle that all objects absorb light from the environment.
 This process frees the electrons within the mineral that remain caught in them.
 Heating to 500 degree C or Higher releases the trapped electrons & produces
light.
 The produced light is measured to determine the last time the item was heated.
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17. • Optically stimulated luminescence (OSL) dating
 Constrains the time when sediment was last exposed to light.
 During sediment transport, exposure to sunlight ‘zeros’the luminescence signal as
natural ambient radiation gradually ionizes mineral grains.
 Carefully sampling under dark conditions allow the sediments to be exposed to
artificial light in the laboratory which releases the OSL signal.
 The amount of luminescence released is used to calculate the age.
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18. • Dendrochronology (Tree ring Dating)
 It is also called as tree ring dating.
 Scientific dating based on analysis of pattern of free rings (growth rings).
 One ring indicates one year.
 It has three areas of application.
I. Paleoecology (used to determine certain aspects of ecologies).
II. Archaeology (Used to date old buildings).
III. Radiocarbon dating (Used to calibrate radiocarbon ages).
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19. • Amino Acid Dating
 Used to estimate age of specimen in pale biology, archaeology, sedimentary
geology and other fields.
 It relates changes in amino acid molecules, to time elapsed since they were
formed.
 Amino acids have two different configurations D & L (Mirror images of each
other).
 Living organisms keep all their amino acids in the "L" configuration.
 When an organism dies, control over the configuration of amino acid ceases, and
the ratio of D to L moves from a value near 0 towards an equilibrium value near 1
 The measuring ratio of D to L in a sample enables one to estimate how long ago
the specimen died.
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20. Relative Dating By:
GHI
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21. • Relative Dating
 Before the use of absolute dating, archaeologists & geologists used this technique
to determine ages of materials.
 It can only determine the events in sequential order (in which not the event
occurred).
 It is still useful technique especially in that materials lacking radioactive isotopes.
 Based on law of superposition.
 Law of superposition states that older layers will be deeper in a site than more
recent layers.
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22. • Stratigraphy
 A technique for relative dating based on organizing remains by means of strata.
 There are many horizontal layers, which are called strata.
 Based on law of super position. Like a layer cake. (Shown in the diagram below).
 Objects in lower strata are older than objects in higher strata.
 It is the oldest of the relative methods.
 Using a few basic principles, it is possible to work out the relative ages of rocks.
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24. • Seriation
 A technique for relative dating by putting groups of objects into sequence in
relation to one another.
 It is the standard method of dating in archaeology.
 Used to date stone tools pottery fragments 7 other art-facts.
 In Europe it has been used frequently to reconstruct the chronological sequence of
graves in cemetery.
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26. • Fluorine Absorption Dating
 It is a method used to determine the amount of time an object has been
underground.
 Fluorine absorption dating can be carried out based on the fact
that groundwater contains fluoride ions.
 Items such as bone that are in the soil will absorb fluoride from the groundwater
over time. From the amount of absorbed fluoride in the item, the time that the item
has been in the soil can be estimated.
 Also a method that measures the amount of fluorine, nitrogen, and uranium in
bones.
 As not all objects absorb fluorine at the same rate, this also undermines the
accuracy of such a dating technique.
 It has a large margin of error.
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27. Applications BY:
JKL
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28. • Applications
 Surface exposure dating is used for the following.
1) Glacial chronologies (alpines, ice sheets)
2) Fluvial chronology (Terraces, inclusion)
3) Shoreline chronology (terraces, lacustrine, marine)
4) Hillslope rates
5) Catchment wide denudation rates
6) Burial chronologies (caves, terraces, paleosols)
7) Landslide chronologies
8) Fault scrap chronologies
9) Volcanic eruptions
10)Desert chronologies
11)Alluvial fan chronologies
12)Archaeology
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30. The End
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