45
DATING METHODS DENDROCHRONOLOGY RADIOCARBON DATING POTASSIUM ARGON DATING LUMINESCENCE DATING ESR DATING FISSION TRACK DATING PROTEIN AND AMINO ACID DIAGENESIS DATING OBSIDIAN HYDRATIAN DATING ARCHEOMAGNETIC DATING SURFACE DATING USING ROCK VANISH e of the most important questions asked about any ancient object is just how old it really is. ere are a number of scientific techniques which can be used to date antiquities

DATING METHODS DENDROCHRONOLOGY RADIOCARBON DATING POTASSIUM ARGON DATING LUMINESCENCE DATING ESR DATING FISSION TRACK DATING PROTEIN AND AMINO ACID DIAGENESIS

Embed Size (px)

Citation preview

Page 1: DATING METHODS DENDROCHRONOLOGY RADIOCARBON DATING POTASSIUM ARGON DATING LUMINESCENCE DATING ESR DATING FISSION TRACK DATING PROTEIN AND AMINO ACID DIAGENESIS

DATING METHODS

DENDROCHRONOLOGY

RADIOCARBON DATING

POTASSIUM ARGON DATING

LUMINESCENCE DATING

ESR DATING

FISSION TRACK DATING

PROTEIN AND AMINO ACID DIAGENESIS DATING

OBSIDIAN HYDRATIAN DATING

ARCHEOMAGNETIC DATING

SURFACE DATING USING ROCK VANISH

One of the most important questions asked about any ancient object is just how old it really is.There are a number of scientific techniques which can be used to date antiquities

Page 2: DATING METHODS DENDROCHRONOLOGY RADIOCARBON DATING POTASSIUM ARGON DATING LUMINESCENCE DATING ESR DATING FISSION TRACK DATING PROTEIN AND AMINO ACID DIAGENESIS

 TARİHLENDİRME YÖNTEMLERİOrganik veya inorganik materiyalleri

Radyokarbon (C-14), Dendrokronoloji-Tree ring dating, Elektron Spin Rezonans (ESR),Termolüminesans (TL) ve OSL gibi arkeometrinin en önemli uygulamaları arasında sayılabilecek yöntemlerle tarihlendirmek mümkündür. Potasyum Argon Metodu (KA): Radyoaktif olan (potasyumun) radyoaktif olmayan Argon40 gazına dönüşmesine dayanır. Özellikle jeolojik tabakalar içinde bulunan fosil kalıntılarına uygulanır. 100.000 yılı aşkın volkanik kayalara da uygulanmaktadır. Radyokarbon Metodu (C-14): 1955' te Amerika'da Chicago Üniversitesi'nde W. Libby ve arkadaşları bu metodu uygulamışlardır. Bu tarihten itibaren en geçerli, en yaygın tarihlendirme metodudur. Özellikle tarih öncesi arkeolojide kullanılır. Tüm organik maddelerde bulunan radyoaktif karbonun, bunların canlılıklarını kaybetmelerinden sonra belirli bir tempoda azaldığı gözlenmiştir. Bu oran bilindiğinden, bulunan organic maddenin yaşı, bu gözönünde tutularak bulunur. Ölçülere göre yaklaşık olarak organik maddelerin ömürlerinin yarısı boyunca yılda 5568 karbon kaybettikleri anlaşılmıştır. Sakıncalı yanı tam doğru netice vermemesidir.Nedeni de atmosferin her zaman aynı miktarda karbon ihtiva etmemesidir. Dendrokronoloji: Amerikalı A.E. Douglass tarafından bulunan, ağaç gövdelerinin enine kesitinde görülen yıllık halka tabakalarının incelenmesine dayanan tarihlendirme yöntemidir. Ağaçlar her yıl gövdesinde yeni bir halka oluşturur. Bu halka bol yağışlı yıllarda kalın, az yağışlı yıllarda ince olur. Douglass eski evlerde kullanılan ağaçlardan özel bir teknikle kesit alarak, üzerlerindeki halkaları sayıp yapıların tarihini saptamayı başarmıştır. Termolüminesans Metodu: Taş, keramik, cam gibi kristal yapıya sahip maddelerin yaş tayininde kullanılır.

Page 3: DATING METHODS DENDROCHRONOLOGY RADIOCARBON DATING POTASSIUM ARGON DATING LUMINESCENCE DATING ESR DATING FISSION TRACK DATING PROTEIN AND AMINO ACID DIAGENESIS

DENDROCHRONOLOGYDendrochronology or tree-ring dating is the method of scientific dating based on the analysis of tree-ring growth patterns. This technique was invented and developed during the 20th century originally by A. E. Douglass,the founder of the Laboratory of Tree-Ring Research at the University of Arizona. The technique can date wood to exact calendar years.

Visible rings result from the change in growth speed through the seasons of the year, thus one ring usually marks the passage of one year in the life of the tree.

Page 4: DATING METHODS DENDROCHRONOLOGY RADIOCARBON DATING POTASSIUM ARGON DATING LUMINESCENCE DATING ESR DATING FISSION TRACK DATING PROTEIN AND AMINO ACID DIAGENESIS

Radiocarbon dating is a radiometric dating method that uses the naturally occurring isotope isotope carbon-14 (14C) to determine the age of carbonaceous materials up to about 60,000 yearsThe technique of radiocarbon dating was discovered by Willard Libby and his colleagues in 1949 during his tenure as a professor at the University of Chicago.

Probably the best known and most frequently used is radiocarbon or 14C dating. Radiocarbon dating can only be applied to organisms that were once alive and is a means of determining how long ago they died. Radiocarbon dating is possible because of the existence in nature of a tiny amount of 14C, or radiocarbon, a radioactive isotope of carbon.  

By measuring how much 14C remains in ancient organic materials, it is possible to calculate how long ago they died. To do this requires extensive chemical processing, carried out in laboratoriesTo convert the carbon in the ancient objects to a form in which the very low level radioactivity can be measured. Most radiocarbon dating is carried out

on bone or charcoal,

as these are the organics that most frequently survive from the past, but many other materials can also be dated using this technique.

Page 5: DATING METHODS DENDROCHRONOLOGY RADIOCARBON DATING POTASSIUM ARGON DATING LUMINESCENCE DATING ESR DATING FISSION TRACK DATING PROTEIN AND AMINO ACID DIAGENESIS

RADIOCARBON DATING

Carbon has two stable, nonradioactive isotopes : carbon-12 (12C), and carbon-13 (13C).

In addition, there are trace amounts of the unstable isotope

carbon-14(14C) on Earth.

Carbon-14 has a half-life of 5730 years and would have long ago vanished from Earth were it not for the unremitting cosmic ray impacts on nitrogen in the Earth's atmosphere, which create more of the isotope.

Page 6: DATING METHODS DENDROCHRONOLOGY RADIOCARBON DATING POTASSIUM ARGON DATING LUMINESCENCE DATING ESR DATING FISSION TRACK DATING PROTEIN AND AMINO ACID DIAGENESIS

                     

  

This 14C isotope is produced in the upper atmosphere by the action of cosmic rays on 14N. This 14C combines with oxygen to produce carbon dioxide (CO2) and is taken in by plants during photosynthesis. From plants this 14C is absorbed into the tissues of every living thing via the food chain. Since it is radioactive, it is unstable and decays away at a known rate. While any plant or animal is alive the 14C lost by radioactive decay is constantly replaced through the food chain, but when that organism dies,no more 14C is taken in, and the amount present in the tissues goes down. (from Aitken 1990)

Page 7: DATING METHODS DENDROCHRONOLOGY RADIOCARBON DATING POTASSIUM ARGON DATING LUMINESCENCE DATING ESR DATING FISSION TRACK DATING PROTEIN AND AMINO ACID DIAGENESIS

POTASSIUM ARGON DATING

Potassium-Argon Dating

is the only technique for dating very old archaeological materials. Geologists have used this method to date rocks as much as 4 billion years old. It is based on the fact that some of the radioactive isotope of Potassium, Potassium-40 (K-40) ,decays to the gas Argon as Argon-40 (Ar-40). By comparing the proportion of K-40 to Ar-40 in a sample of volcanic rock, and knowing the decay rate of K-40, the date that the rock formed can be determined.   

Page 8: DATING METHODS DENDROCHRONOLOGY RADIOCARBON DATING POTASSIUM ARGON DATING LUMINESCENCE DATING ESR DATING FISSION TRACK DATING PROTEIN AND AMINO ACID DIAGENESIS

In principle all the materials containing quartz or feldspars and submitted to

heating to several hundreds of degrees centigrate can be dated by this way

Page 9: DATING METHODS DENDROCHRONOLOGY RADIOCARBON DATING POTASSIUM ARGON DATING LUMINESCENCE DATING ESR DATING FISSION TRACK DATING PROTEIN AND AMINO ACID DIAGENESIS

LUMINESCENCE DATING

Materials with suitable luminescence properties can be dated because at some point in the past traps are emptied of their charge by sufficient exposure to heat or light.

Subsequently, traps become refilled because of continued ionization by radioactivity and a latent luminescence signal steadily accumulates

Optical dating is method of determining how long ago minerals were last exposed to daylight, It is useful to geologists and archaeologists who want to know when such an event occurred. Time clock become zero for a sediment of earthquake line,or sediment of loess.

Thermo luminescence dating is method of determining how long ago minerals heated to 800-1000°C degrees; then when heated time clock become zero (for making pottery or baked brick)

Page 10: DATING METHODS DENDROCHRONOLOGY RADIOCARBON DATING POTASSIUM ARGON DATING LUMINESCENCE DATING ESR DATING FISSION TRACK DATING PROTEIN AND AMINO ACID DIAGENESIS
Page 11: DATING METHODS DENDROCHRONOLOGY RADIOCARBON DATING POTASSIUM ARGON DATING LUMINESCENCE DATING ESR DATING FISSION TRACK DATING PROTEIN AND AMINO ACID DIAGENESIS
Page 12: DATING METHODS DENDROCHRONOLOGY RADIOCARBON DATING POTASSIUM ARGON DATING LUMINESCENCE DATING ESR DATING FISSION TRACK DATING PROTEIN AND AMINO ACID DIAGENESIS
Page 13: DATING METHODS DENDROCHRONOLOGY RADIOCARBON DATING POTASSIUM ARGON DATING LUMINESCENCE DATING ESR DATING FISSION TRACK DATING PROTEIN AND AMINO ACID DIAGENESIS
Page 14: DATING METHODS DENDROCHRONOLOGY RADIOCARBON DATING POTASSIUM ARGON DATING LUMINESCENCE DATING ESR DATING FISSION TRACK DATING PROTEIN AND AMINO ACID DIAGENESIS
Page 15: DATING METHODS DENDROCHRONOLOGY RADIOCARBON DATING POTASSIUM ARGON DATING LUMINESCENCE DATING ESR DATING FISSION TRACK DATING PROTEIN AND AMINO ACID DIAGENESIS
Page 16: DATING METHODS DENDROCHRONOLOGY RADIOCARBON DATING POTASSIUM ARGON DATING LUMINESCENCE DATING ESR DATING FISSION TRACK DATING PROTEIN AND AMINO ACID DIAGENESIS
Page 17: DATING METHODS DENDROCHRONOLOGY RADIOCARBON DATING POTASSIUM ARGON DATING LUMINESCENCE DATING ESR DATING FISSION TRACK DATING PROTEIN AND AMINO ACID DIAGENESIS
Page 18: DATING METHODS DENDROCHRONOLOGY RADIOCARBON DATING POTASSIUM ARGON DATING LUMINESCENCE DATING ESR DATING FISSION TRACK DATING PROTEIN AND AMINO ACID DIAGENESIS
Page 19: DATING METHODS DENDROCHRONOLOGY RADIOCARBON DATING POTASSIUM ARGON DATING LUMINESCENCE DATING ESR DATING FISSION TRACK DATING PROTEIN AND AMINO ACID DIAGENESIS
Page 20: DATING METHODS DENDROCHRONOLOGY RADIOCARBON DATING POTASSIUM ARGON DATING LUMINESCENCE DATING ESR DATING FISSION TRACK DATING PROTEIN AND AMINO ACID DIAGENESIS
Page 21: DATING METHODS DENDROCHRONOLOGY RADIOCARBON DATING POTASSIUM ARGON DATING LUMINESCENCE DATING ESR DATING FISSION TRACK DATING PROTEIN AND AMINO ACID DIAGENESIS
Page 22: DATING METHODS DENDROCHRONOLOGY RADIOCARBON DATING POTASSIUM ARGON DATING LUMINESCENCE DATING ESR DATING FISSION TRACK DATING PROTEIN AND AMINO ACID DIAGENESIS
Page 23: DATING METHODS DENDROCHRONOLOGY RADIOCARBON DATING POTASSIUM ARGON DATING LUMINESCENCE DATING ESR DATING FISSION TRACK DATING PROTEIN AND AMINO ACID DIAGENESIS
Page 24: DATING METHODS DENDROCHRONOLOGY RADIOCARBON DATING POTASSIUM ARGON DATING LUMINESCENCE DATING ESR DATING FISSION TRACK DATING PROTEIN AND AMINO ACID DIAGENESIS

In phosphorescence the energy difference between the excited state and themeta stable state is generally so small that detrapping occurs by lattice vibra-tions at ambient temperature, i.e. no external supply of energy is required.

However, in TL and OSL the energy difference between the excited stateand the meta stable state is so large that external energy must be appliedto detrap the electrons. In TL the luminescence emission is accelerated bythermal stimulation whereas in OSL the luminescence emission is accelerated by optical stimulation.

Page 25: DATING METHODS DENDROCHRONOLOGY RADIOCARBON DATING POTASSIUM ARGON DATING LUMINESCENCE DATING ESR DATING FISSION TRACK DATING PROTEIN AND AMINO ACID DIAGENESIS

LUMINESCENCE DATING

As far as dating is concerned, the phenomenon of luminescence can be subdivided according to the kind of energy supply during stimulation into

• thermoluminescence (TL, stimulated by heat)

• optical stimulated luminescence (OSL, stimulated by visible light)

• infrared stimulated luminescence (IRSL, stimulated by infrared light)

ELSEC 9010 osl device

Page 26: DATING METHODS DENDROCHRONOLOGY RADIOCARBON DATING POTASSIUM ARGON DATING LUMINESCENCE DATING ESR DATING FISSION TRACK DATING PROTEIN AND AMINO ACID DIAGENESIS

Basic Concepts in Luminescence

Luminescence is a generic term for the electromagnetic radiation (usually in the form of visible light) emitted as a consequence of an atomic or molecular non-thermal excitation. Thus, luminescence is often described as cold light to distinguish it from incandescent light emission, which occurs when a material is excited thermally. Luminescent materials are able to absorb energy, store part of it and convert it into light; these materials usually have a crystalline structure.

Page 27: DATING METHODS DENDROCHRONOLOGY RADIOCARBON DATING POTASSIUM ARGON DATING LUMINESCENCE DATING ESR DATING FISSION TRACK DATING PROTEIN AND AMINO ACID DIAGENESIS

Luminescence can broadly be categorised as either Fluorescence or phospho-rescence. Fluorescence: the light emission resulting from the relaxation of an electron from an excited state to the ground state (possibly through a metastable state from which transition to the ground state is allowed). The delay between the absorption of energy resulting in the excited state and the emission is determined by the life time of the excited state.The life time can be as short as picoseconds and as long as milliseconds in special cases. Photoluminescence, cathodo luminescence, chemi-luminescence, bioluminescence and triboluminescence are all examples of different fluorescence processes with different means of excitation(i.e. photons, electrons, chemical energy, biochemical and mechanical energy, respectively)

Phosphorescence: the relaxation back to the ground state is delayed by a relaxation to the ground state is not permitted. These meta stable states function as electron traps, and energy must be supplied to detrap (release) the electrons back to the excited state from where they can relax to the ground state (McKinlay, 1981). The return to the ground state is thus delayed for period of time; the length of which depends on the life time of the electron in the meta stable state.

The two types of luminescence

are distinguished by the atomic mechanisms

whereby the light is emitted.

Page 28: DATING METHODS DENDROCHRONOLOGY RADIOCARBON DATING POTASSIUM ARGON DATING LUMINESCENCE DATING ESR DATING FISSION TRACK DATING PROTEIN AND AMINO ACID DIAGENESIS

How stimulation occurs

With optical dating,the signal is obtained by exposure to a beam of blue /green light or infrared radiation.

Optically-stimulated luminescence(OSL) is commonly used , also it is calling as Photon stimulated luminescence (PSL) and Photoluminescence(PL)

Page 29: DATING METHODS DENDROCHRONOLOGY RADIOCARBON DATING POTASSIUM ARGON DATING LUMINESCENCE DATING ESR DATING FISSION TRACK DATING PROTEIN AND AMINO ACID DIAGENESIS

Optically stimulated luminescence relies on the same basic concepts as TL,

but in OSL the stimulation energy is supplied by photons instead of heat.

Thus, the physical principles of OSL are closely related to those of TL. How-

ever, it is not clear that the same defect centres are involved in both processes

in any one material (McKeever, 2001). OSL has several advantages over TL.

When dealing with unheated materials (i.e. materials zeroed by light ex-

posure) the most important of these advantages are that in OSL only the

trapping levels most sensitive to light are sampled; that is the charge popula-

tion most e®ectively zeroed. In many samples, it is believed that 99% of the

initial OSL signal originates from the 325 ±C TL peak in quartz (Murray and

Wintle, 1999). Another advantage of OSL over TL is that stimulation can be

performed at room temperature (although some advantages may be obtained

at slightly elevated temperatures), which means that thermal quenching is

not made worse by heating.

Page 30: DATING METHODS DENDROCHRONOLOGY RADIOCARBON DATING POTASSIUM ARGON DATING LUMINESCENCE DATING ESR DATING FISSION TRACK DATING PROTEIN AND AMINO ACID DIAGENESIS

Trap mechanismTrap mechanism, namely the time-dependent accumulation of electrons and holes in the crystal lattice of certain common minerals (trap). The minerals are acting as natural radiation dosimeters. When a mineral is formed or reset, all electrons are in the ground state. Naturally occurring radioactive isotopes (U, Th, and K) emit a variety of rays which ionize atoms. Negatively charged electrons are knocked off atoms in the ground state (valence band) and transferred to a higher energy state (conduction band); positively charged holes remain near the valence band.

Trap schematic

The trapped electrons and holes forms luminescence centres which can be stimulated. For the measurement of a luminescence signal, the trapped electrons have to be either thermally (by heating) or optically (by light exposure) activated. The electrons return to the conduction band and most of them will recombine with the holes. If such holes are luminescence centres, light emission (luminescence) is observed.

Page 31: DATING METHODS DENDROCHRONOLOGY RADIOCARBON DATING POTASSIUM ARGON DATING LUMINESCENCE DATING ESR DATING FISSION TRACK DATING PROTEIN AND AMINO ACID DIAGENESIS

Zeroing a trap

• Figure show the basic principles of the dating process. A zeroing event resets any previously stored trapped electrons - this resetting may be heating, exposure to sunlight or mineral formation. After zeroing, new electrons and holes are trapped as a result of natural radiation

Page 32: DATING METHODS DENDROCHRONOLOGY RADIOCARBON DATING POTASSIUM ARGON DATING LUMINESCENCE DATING ESR DATING FISSION TRACK DATING PROTEIN AND AMINO ACID DIAGENESIS

References

• Chronometric Dating in Archaelogy (Edited by R.E.Taylor and Martin j.Aitken)

• Archaeological dating using physical phenomena(M.J. Aitken)

Page 33: DATING METHODS DENDROCHRONOLOGY RADIOCARBON DATING POTASSIUM ARGON DATING LUMINESCENCE DATING ESR DATING FISSION TRACK DATING PROTEIN AND AMINO ACID DIAGENESIS

Electron spin resonance

Page 34: DATING METHODS DENDROCHRONOLOGY RADIOCARBON DATING POTASSIUM ARGON DATING LUMINESCENCE DATING ESR DATING FISSION TRACK DATING PROTEIN AND AMINO ACID DIAGENESIS

ESR DATING Electron spin resonance (ESR)

was proposed as a dating method by Zeller as early as 1967, but its practical application began with the work of Ikeya in 1975.Study based on carbonate materials, bones, and quartz

ESR-dating is a powerful tool to date the time of mineralization, sedimentation or last heating of minerals. The dating method has the same dosimetric basis as TL/OSL, but in contrast to these methods only paramagnetic centers are detected with ESR. As the measurement does not destroy the centers however, it can be repeated several times.

Figure 1: Created by ionising radiation, point defects accumulate predictably in enamel. Imperfections in the crystal lattice exist between the valence and conduction bands, trapping free radicals

Page 35: DATING METHODS DENDROCHRONOLOGY RADIOCARBON DATING POTASSIUM ARGON DATING LUMINESCENCE DATING ESR DATING FISSION TRACK DATING PROTEIN AND AMINO ACID DIAGENESIS

FISSION TRACK DATING

• Fission track dating is a radiometric dating technique based on analyses of the damage trails, or tracks, left by fission fragments in certain uranium bearing minerals and glasses.

• Uranium-238 undergoes spontaneous fission decay at a known rate. The fragments emitted by this fission process leave trails of damage in the

crystal structure of the minerals

enclosing the uranium Fission tracks in an apatite crystal (top) and in a muscovite mica (bottom).

Page 36: DATING METHODS DENDROCHRONOLOGY RADIOCARBON DATING POTASSIUM ARGON DATING LUMINESCENCE DATING ESR DATING FISSION TRACK DATING PROTEIN AND AMINO ACID DIAGENESIS

FISSION TRACK DATING

• Etching of polished surfaces of these minerals reveals the spontaneous fission tracks for counting by optical microscopic means. The number of tracks correlates directly with the age of the sample and the uranium content

Fission Tracks (FT) are micrometer-sized, linear damage tracks that occur in insulating minerals and that are caused by the spontaneous fission of heavy, unstable nuclides (mostly 238U in natural minerals). The spontaneous fission of 238U occurs at a specific rate, described by the decay constant (l f = 8.46 ´ 10-17a-1). This implies that when the uranium concentration (CU) of a sample is known, the spontaneous FT density (r s = number of tracks/cm2) in that sample is an indication for the sample’s age. r s is determined by counting the tracks under an optical microscope (at 1250 ´ magnification). Since FTs are features at an atomic scale, they require chemical techniques (etching) to make them observable under the optical microscope. CU is measured by irradiating the sample in a nuclear reactor with thermal neutrons

Page 37: DATING METHODS DENDROCHRONOLOGY RADIOCARBON DATING POTASSIUM ARGON DATING LUMINESCENCE DATING ESR DATING FISSION TRACK DATING PROTEIN AND AMINO ACID DIAGENESIS

PROTEIN AND AMINO ACID DIAGENESIS DATING

• At a widely publicized news conference in August of 1972, Dr. Jeffrey Bada of Scripps Institute of Oceanography announced the "discovery" of a new dating method based on the rate of racemization of amino acids in fossil material. He was quoted as saying that he had discovered the basis of the method in 1968, and that it was so obvious and simple he was amazed it hadn't been discovered earlier. Amino acids are the "building

blocks," or sub-units, of proteins. About 20 different kinds of amino acids are found in proteins. All amino acids in proteins (except glycine) are L-amino acids. These amino acids spontaneously tend to slowly change to the D-form. The D-form tends to revert to the L-form, and eventually an equilibrium is obtained, as illustrated here for alanine

Page 38: DATING METHODS DENDROCHRONOLOGY RADIOCARBON DATING POTASSIUM ARGON DATING LUMINESCENCE DATING ESR DATING FISSION TRACK DATING PROTEIN AND AMINO ACID DIAGENESIS

PROTEIN AND AMINO ACID DIAGENESIS DATING

• The process by which an L-amino acid changes into a mixture of the L- and D-forms (or the D-form changes into a mixture of the L- and D-forms) is called racemization. Racemization is complete when equal amounts of the L- and D-forms are obtained. Hare and Mitterer3 measured the rate of racemization of L-isoleucine to D-

alloisoleucine in modern shell fragments heated in water at high temperatures and extrapolated these data to lower temperatures in order to estimate the rate of racemization of L-isoleucine in fossil shells to obtain what they believed to be an approximate age for these fossil shells.

These data are believed to yield the rates at which L-isoleucine was converted to Dalloisoleucine in the sediment through geological time. The extent of conversion of L-isoleucine to D-alloisoleucine in core sediment samples from various depths was then determined and conclusions based on the above rates were used to estimate the ages of the sediments from various core depths

Page 39: DATING METHODS DENDROCHRONOLOGY RADIOCARBON DATING POTASSIUM ARGON DATING LUMINESCENCE DATING ESR DATING FISSION TRACK DATING PROTEIN AND AMINO ACID DIAGENESIS

OBSIDIAN HYDRATIAN DATING

The obsidian hydration dating method was introduced to the archaeological community in 1960 by Irving Friedman and Robert Smith of the U. S. Geological Survey (Friedman and Smith 1960). The potential of the method in archaeological chronologic studies was quickly recognized and research concerning the effect of different variables on the rate of hydration has continued to the present

day by Friedman and others.

Obsidian hydration rim (between arrows)

Page 40: DATING METHODS DENDROCHRONOLOGY RADIOCARBON DATING POTASSIUM ARGON DATING LUMINESCENCE DATING ESR DATING FISSION TRACK DATING PROTEIN AND AMINO ACID DIAGENESIS

OBSIDIAN HYDRATIAN DATING• When a new surface of obsidian is exposed to the atmosphere, such as during the

manufacture of glass tools, water begins to slowly diffuse from the surface into the interior of the specimen. When this hydrated layer or rind reaches a thickness of about 0.5 microns, it becomes recognizable as a birefringent rim when observed as a thin section under a microscope. Hydration rims formed on artifacts can vary in width from less than one micron for items from the early historic period to nearly 30 microns for early sites in Africa (Michels et al. 1983a; Origer 1989).

Once a hydration layer has been measured, it can be used to determine the relative ages of items or, in some circumstances, can be converted into an estimated absolute age. In order to transform the hydration rim value to a calendar age, the rate of the diffusion of water into the glass must be determined or estimated. The hydration rate is typically established empirically through the calibration of measured samples recovered in association with materials whose cultural age is known or whose age can be radiometrically determined, usually through radiocarbon dating methods (Meighan 1976).

Page 41: DATING METHODS DENDROCHRONOLOGY RADIOCARBON DATING POTASSIUM ARGON DATING LUMINESCENCE DATING ESR DATING FISSION TRACK DATING PROTEIN AND AMINO ACID DIAGENESIS

ARCHEOMAGNETIC DATING

An absolute dating method based on the earth's shifting magnetic poles. When clays and other rock and soil materials are fired to approximately 1300°F (700°C) and allowed to cool in the earth's magnetic field, they retain a weak magnetism which is aligned with the position of the poles at the time of firing. This allows for dating, for example, of when a fire pit was used, based on the reconstruction of pole position for earlier times.

Paleomagnetism is concerned with the history of the Earth's magnetic field during geologic time,and applications to geological and geophysical problems.Archeomagnetism involves the study of the Earth's magnetic field during archaelogical time,and the application of paleomagnetic techniques and principles to archaeological features and artifacts (Tarling 1983)

Page 42: DATING METHODS DENDROCHRONOLOGY RADIOCARBON DATING POTASSIUM ARGON DATING LUMINESCENCE DATING ESR DATING FISSION TRACK DATING PROTEIN AND AMINO ACID DIAGENESIS

SURFACE DATING USING RACK VANISH

• Rock vanish ,a dark colored,magnesium-,iron-,and silica-rich coating that forms on exposed rock surfaces over time, especially in arid and semi-arid regions,has been used as a chronometric dating tool in both archeology and geology.

• The methods most commonly employed are cation-ratio dating ,using differential leaching of cations in the varnish coating ,and accelerator mass spectrometry-based radiocarbon dating of organic material contained within or trapped beneath the varnish coating.

Page 43: DATING METHODS DENDROCHRONOLOGY RADIOCARBON DATING POTASSIUM ARGON DATING LUMINESCENCE DATING ESR DATING FISSION TRACK DATING PROTEIN AND AMINO ACID DIAGENESIS
Page 44: DATING METHODS DENDROCHRONOLOGY RADIOCARBON DATING POTASSIUM ARGON DATING LUMINESCENCE DATING ESR DATING FISSION TRACK DATING PROTEIN AND AMINO ACID DIAGENESIS

Some terminology

Chronology is the science of locating events in time.

An arrangement of events from either earliest to latest or

the reverse

Page 45: DATING METHODS DENDROCHRONOLOGY RADIOCARBON DATING POTASSIUM ARGON DATING LUMINESCENCE DATING ESR DATING FISSION TRACK DATING PROTEIN AND AMINO ACID DIAGENESIS

Archaeological stratigraphy • In the field of archaeology, soil stratigraphy is used

to better understand the processes that form and protect archaeological sites. The law of superposition holds true, and this can help date finds or features from each context, as they can be placed in sequence and the dates interpolated. Phases of activity can also often be seen through stratigraphy, especially when a trench or feature is viewed in section (profile). As pits and other features can be dug down into earlier levels, not all material at the same absolute depth is necessarily of the same age, but close attention has to be paid to the archeological layers.