Biblical Archeology, Volume 2

Dating Techniques in Archeology: An Intro

Dr. Johnson C. Philip

Dr. Saneesh Cherian

Editor: JW Thompson

5th Revised Edition, 2013

Contents

Biblical Archeology, Volume 2 Dating Techniques in Archeology: An Intro

Dr. Johnson C. Philip Dr. Saneesh Cherian

Introduction

Initial Problems Faced In Dating:

Development Of Dating In Archeology

Dating Techniques Used By Archeologists

Introduction To Relative Dating Methods

Cultural Affiliation Dating:

Cation Ratio Dating:

Fluorine Dating:

Obsidian Hydration Dating:

Patination Dating:

Pollen Analysis:

Rate Of Accumulation:

Seriation:

Varve Analysis:

Absolute Dating Techniques

Archeomagnetism:

Astronomical Dating:

Dendrochronology:

Electron Spin Resonance:

Fission Track Dating:

Opacity Stimulation Luminescence:

Oxidizable Carbon Ratio:

Racemization:

Thermoluminescence:

Radio Carbon Dating:

Introduction

In the first volume we discussed the importance and the benefits of archeology for Bible Students. One of the important activities in archeology is age-determination.

An artifact, an inscription, or a mummy can be placed in historical context and interpreted only if one can speak with some certainty about what period it belongs to. The closer an object is to an event, the better one can interpret the event or the object, and the farther it is the less its relation to the given event. A cult object found from the home-town of Abraham, but used only two millennia after the time of the Patriarch, would throw less specific light on his life and more on the culture millennia after him.

Finding the collapsed walls of ancient Jericho is exciting. But this discovery is useless for Biblical archeology unless it can be demonstrated that this even happened within the dates specified by the Biblical historian. If someone can definitely establish that the discovered event happened 500 years before or after the dates demanded by the Bible, it automatically becomes useless for a possible correlation with the conquest mentioned in the Bible.

Thus attempts to develop methods to ascertain dates of artifacts and events have always been there right from the beginning of Archeology. Initially it was sufficient to know the country of origin and the general era, but as archeology was increasingly used to reconstruct ancient history with a measure of certainty, more accurate dates became important. But since most of the earlier archeological investigations were not done systematically, this immediately posed a problem.

Initial Problems Faced In Dating: Since the initial excavations [for almost a century] were done haphazardly, the work of the archeologists was often no different from the grave-robbers. One robbed it, while the other plundered it, but both of them did it for personal gains. Thus most archeological diggings were unplanned and random, without any substantial record-keeping, and the eyes were fixed only on "major" artifacts. Things considered minor such as pot-shreds and pieces of bones and food were simply thrown away. Much evidence that could lead to reliable dating [especially with the help of Radiocarbon Dating] were lost for ever.

Further, since the artifacts were seen more as collectibles rather than objects of historical study, and since in those days the finders were keepers, the items discovered were simply divided among the collaborators. Some ended in their personal collection, while others were sold to status-conscious people in Europe and America, and some were even presented to rulers of various countries as souvenirs. This immediately destroyed the context in which these artifacts were found, destroying the opportunity to correlate them in any objective way, for if one of them could be dated in the place of discovery with certainty, the others could also be dated.  Such an opportunity is lost for a large number of precious finds.

Worse, though many of the items now rest in museums where people [or researchers] can have access to them, a large number of the more attractive and precious artifacts have found their way into private collections of antique collectors worldwide. Most of them zealously guard their treasures, and do not give access to these for any purpose. Often when some of these people pass away,  everything falls into the hands of their heirs who might have no appreciation for their historical value. Faced with the need to raise funds for their pet projects, or even to finance their vices, they often sell these in the antique black market. Others simply dump them in their attics, remaining lost for long time, or are even destroyed by people who have no idea of their historical value.

A good example what might happen to ancient artifacts in private possession is the story of what is popularly called Jenkins Venus. An ancient statue of goddess Venus, it was considered so precious by the original buyer that he had an entire Roman style building specially commissioned to house the statue. But his heirs did not have money to maintain it all, and sold it in auction at close to eight million pounds [approximately 15 million US Dollars].

Once some order came into archeological excavations, and once people started to reconstruct ancient history of places from where such finds came, the importance of dating them in situ grew upon them. It is only then that methods of dating began to be developed. However, this happened so late that even today a large number of finds available for public research still await more precise dating.

Development Of Dating In Archeology

Archeology is a science that has its origin in grave-robbers, antique hunters, status conscious collectors, gold-seekers, and the quacks who used ground-up mummies as cure for a number of diseases. Thus an attempt at dating was not usually done even by those who collected ancient artifacts for more serious purposes. However, with the development of interest in the history of ancient civilizations, there were some attempts to date finds in a more precise manner. This  was, however, hindered by the random manner in which most of the earlier "academically oriented" excavations were conducted.

Flinders Petrie

Serious development of dating took place for the first time in 1890 when Flinders Petrie started work at Tell el Hesi. He drew attention of excavators to the fact that most mounds in the middle east were not a single ruined town, but rather a series of ruined towns one on top of the other, with the oldest one at the bottom and the most recent one at the top. Maybe the last town on top was ruined because it was abandoned, but almost all the previous ones were ruined after the town was defeated by enemy forces. And most invaders had the habit of rebuilding over the ruins of the conquered town, after they raged most of it to a suitable level. Nothing was thrown away, and everything from the defeated town became part of the filling.

Tell el-Hesi

Thus if a vertical shaft is dug carefully, one would see several distinct layers one below the other till one reached the virgin soil or bedrock.  This became obvious at Tell el Hesi where a wadi [deep cut formed by erosion of mud and brick] exposed an entire vertical section of the mound, and several distinct layers were visible. Petrie measured the relative height of the layers from mean sea level, and created a chronology which was then applied to other places close by.

Example of Multiple Layers

FJ Bliss, who followed Petrie to work at this site reinvestigated, and established that the method gave some good results. In 1894 he combined the results of his work with that of Petrie, and established a rough chronology as far back as 1500 BC. However, soon it became obvious that this method is good only for a limited area because the scale established in one region might not have any correlation with the strata in mounds far removed from the first ones. Further, the method fell short of the goal in dating layers in those mounds where the layers overlapped, where they were not sufficiently horizontal, or where some layers were missing [because there was simply no human habitation there for several hundred years].  In spite of this weakness this method brought in quite some order in the chaotic chronology of the Tells investigated, but the need for a more accurate and objective chronology soon became obvious.  The next important development was Pottery-based-dating.

Ancient Palastinian Pottery (Pic By: Ad Meskens)

Using pottery for dating might surprise many, but this need not be so. A comparison of pottery obtained from several cultures will immediately show even to the initiated layman that they exhibit distinct characteristics. This being so, a researcher can deduce much more information in a reliable manner, especially when an abundance of pottery is discovered from the same site. And this is often the case because pottery happens to be the most essential item in all ancient houses. Since they were mud or clay-based, they were relatively cheap. But once broken, they are of no use. Such pieces, often thrown into common dumps, survive unchanged for millennia.  And when there is plenty of sample material, it makes deductions all the more objective.

Pottery-based Dating was pioneered, among others, by WF Albright. He was actively involved in the archeology of Palestine from 1920 to 1936. An exceptionally bright scientist, he had the special ability to apply information from several areas of knowledge into archeology. Because of this special ability, he took up an extensive study of pottery discovered from numerous places, compared their shapes, the available absolute dates related to them, the available relative dates, and so on, and proposed a pottery-based chronology based upon this exhaustive information.

Much of the result of this pioneer study was visible in his publication on the pottery of Tell Beit Mirsim in 1932 and 33.  In it he was able to explain the chronology-determination based upon his study of Palestinian pottery. This work was then taken up and both expanded and refined by many others.

Though Pottery-based Dating was initially established only for Palestine, the work was eventually expanded to, and correlated with, the pottery of Egypt, Babylon, Mesopotamia, and practically all of the lands which are important for Bible studies. What's more, scribes based in countries like Egypt have left behind so many absolute dates [based upon lunar and solar eclipse, king lists, etc] that these can be used to calibrate the Pottery-based chronology of Egypt to a very high level of accuracy. This in turn can be used to compare potter found in those countries which had plenty of interaction with Egypt, as Egyptian pottery would find a place in these countries also. When this pottery is compared with the local ones, their dates can be determined with some certainty, and so on.

As a result of decades of careful work on pottery, correlated with absolute chronologies, helped by discoveries of modern science of dating, and compared with neighboring countries, Pottery-based Dating has become an important component of dating in Biblical lands.

Pottery-based Dating is only one of the many archeological dating methods available. It has been described here in so much detail mainly because of its close relation with, and development from, the process of archeological discovery itself. However, numerous other methods of dating are also available, and they are often used individually or with other methods to arrive at dates that are as accurate as possible.  The most important ones among these are described below.

Dating Techniques Used By Archeologists

Dozens of techniques are now applied, often more than one to the same object, to determine the dates as accurately as is possible. These techniques can be divided into two: relative dating methods and absolute dating methods. As is obvious from the name, the latter gives more accurate results compared to the former.

One should realize that not all methods can be used for dating all kinds of discoveries. Further, some of them, such as Cultural Affiliation Dating, can be used on a wide variety of artifacts whereas some such as Radio-Carbon Dating can be used only on things having a biological origin. But then this should not surprise any because tools of science have both their range as well as their boundaries.

The major Relative and Absolute methods of dating used in archeology are as follows:

Relative Dating Techniques

** Cultural Affiliation

** Cation Ratio

** Fluorine Dating

** Obsidian Hydration

** Patination

** Pollen Analysis

** Rate Of Accumulation

** Seriation

** Varve Analysis

Absolute Dating Techniques

** Archeomagnetism

** Astronomical Dating

** Dendrochronology

** Electron Spin Resonance

** Fission Track

** Opacity Stimulation Luminescence

** Oxidizable Carbon Ratio

** Racemization

** Thermoluminiscence

** Radio-Carbon Dating

Introduction To Relative Dating Methods

Dozens of techniques are now applied, often more than one to the same object, to determine the dates as accurately as is possible. These techniques can be divided into two: relative dating methods and absolute dating methods. As is obvious from the name, the latter gives more accurate results compared to the former.

One should realize that not all methods can be used for dating all kinds of discoveries. Further, some of them, such as Cultural Affiliation Dating, can be used on a wide variety of artifacts whereas some such as Radio-Carbon Dating can be used only on things having a biological origin. But then this should not surprise any because tools of science have both their range as well as their boundaries.

The major Relative and Absolute methods of dating used in archeology are as follows:

Cultural Affiliation Dating:  Each culture has its own discernible peculiarities, that change with time, so that an observer [who already knows about that culture] can see an object, hear about a practice, come across a word, and tell the approximate time-period to which it belongs. A good example is the English language.

The language of a drama, novel, or book written during the  Elizabethan period will  resemble the language in a remarkable way. Thus if one comes across an ancient manuscript that uses this type of a language, then one can safely assume that it is at least three to four hundred years. Of course, before coming to that conclusion once has to rule out many factors that can create apparent age. For example, one has to make sure that it is not a mock-writing done by a modern writer for some purpose such as a school assignment or a satire in older English but meant for consumption by the present readers.

Artifacts produced by various cultures, and similar tangible items, have come in so abundantly, and their styles and other discernible factors have been studied in detail that is so sufficient, that experts can often ascribe a tentative date within a day of the discovery. Surprisingly, this method of dating can be used on an extremely wide variety of artifacts, inscriptions, clothing, pictures, and even languages.

Cultural Affiliation Dating can give good results in the hands of a careful researcher, specially if he has plenty of experience with this kind of dating, and if he has a large number of artifacts [large sample, speaking technically] to conduct this study. Often CAD can be a good starting-point, and from there one can move on to more accurate and exacting techniques.

CationRatio Dating:   Rocks exposed to the elements of nature gradually become coated with a layer of special chemicals. This "rock varnish" is formed when calcium and potassium seep out of the rocks, which  undergo predictable chemical changes, and quote the surface to a thickness that is somewhat proportional to the time for which the rock has been exposed to natural elements.

When someone carves a picture over such a rock,  the "rock varnish" is removed from the area of rock that is removed through carving, whereas it keeps growing in areas untouched by the carving. Once the carved area is exposed to nature, a fresh coat of the so-called rock-varnish begins to form over the carved area. Thus if one is able to get to two surfaces, the one always exposed to elements and the one that has a younger coating after the carving, one can come to some conclusions about how long the carving has been there on the rock.

To do so, they scrape the varnish-like coating from the virgin rock surface and also from the carved surface, and obtain the ration between the positively charged ions [cations] in the samples. This ratio gives some idea of the age of the carving.

Cation Ratio dating is a relative method, and it has many uses, but it can never give absolute dating. Further, cation formation is affected by soil, moisture, and other chemical factors that affect it over the years. Thus tests are conducted on a large sample of rocks from a given geographical area [with some carvings, if possible, with a known date] and a calibration-chart is prepared. This chart then helps the investigators to come up with dates that are still relative, but which are more reliable.

Fluorine Dating:  Fluorine is an element found abundantly in groundwater in most places around the world. When men and animals are buried in soil rich with water content, the skeletal remains are inundated with a host of chemicals circulating through the ground water. Fluorine begins to accumulate in these bones through a complex chemical process. The accumulation of Fluorine is somewhat proportional to the time for which the skeleton remains buried underground.

This method for relative dating is now several decades old, and techniques are available for accurately assessing the amount of Fluorine that has accumulated in buried bones or implements made of bone [which are abundant in archeological remains]. Once a Fluorine profile of bones found in single location [or even an entire geographical area] is prepared, it can be used to place those skeletal remains in relation to each other in time.  Thus though this method offers only relative dating, it offers a highly accurate method for establishing the general chronology of skeletal finds in relation to each other.

The famous Piltdown Hoax was exposed with the help of this method. Piltdown Man is the name given to the hypothetical "Missing Link" in human evolution discovered in Piltdown, England. More than 500 learned works appeared on this missing link and even a monument was erected in the place of its discovery to commemorate this find. However, once the discover of this "missing link" died, the bones [so far zealously hidden from the scientific community, who were given only plaster casts for their study] came into the possession of the scientific community for the first time. A series of Fluorine dating, and they found this "ape man" was a composite fabricated by mixing bones from various ages. Thus even relative dating have substantial scientific contributions to make.

Obsidian Hydration Dating:   This is a relatively new dating method, developed around 1960. Though the primary purpose of this technique is to find relative dates, at times it gives dates that are as good as absolute. It also happens to be more easy to conduct, and cost effective in most cases.

Obsidian is a natural glass, formed by volcanic activity. During earlier part of the human civilization, when hardened metal implements were not available, Obsidian was highly prized for its ability to cut and shape implements. It has been found in the mountains of Americas, Europe, Near East to India, North East Asia to Japan and even New Zealand. A large number of Obsidian artifacts have been discovered in all these places.

The Obsidian Dating is based upon a special characteristic of this material. As soon as there is a fracture in this material. that new surface begins to absorb water [hydration] at a level that is almost constant with time. The thickness of this hydration layer increases with time, and this time can be determined by cutting a thin piece of this material which is then examined under microscope.

The method yields only relative dates, but they are more reliable than dates given by many other methods. The cost is also less. But it needs to be used with care as the rate of hydration can be affected by many factors. Even in the laboratory the test is often repeated after one week on the same sample before the final result is declared.

PatinationDating:  Many ancient artifact develop a thin outer layer of chemicals called the patina. The patina is the outermost surface of the artifact. This layer differs in color, texture, luster or composition from the rest of the artifact.  This layer is created as a result of chemical, physical or biological change in response to the surrounding soil and environmental condition. When a large number of artifacts with patina are found in the same location, this layer can be used to gauge their ages relative to each other.

A good  example of patination would be a flint artifact buried in some type of soil or sediment that causes its surface to be chemically altered and become white, yellow or brown. Another example would be the green crust that forms on bronze. Similar examples are known to even those who do not work with archeological samples.

So far five types of patination have been recognized and investigation. The first is bleaching, which is caused by the leaching out silica and replacement of it with lime salts. The second is induration of exposed surfaces, which is caused by the leaching out of soluble silica and redeposition of it at the surface forming a substance called silcrete. The third is limonite-penetration and staining which involves limonite clays and salts in the soil being absorbed by stone artifacts. The fourth can be called "desert-varnish" which is a condition created by extreme dryness and intense solar radiation affecting artifacts. Fifth  is the formation of a crust, caused by leaching out iron salts and redeposition at the surface.

With a site that has several layers of civilizations and a large series of objects from each layer, it is possible to observe obvious differences in the amounts of patina. With this knowledge the layer may be determined from the earliest to the latest civilization. However, work is going on to identify possible yearly-deposit-layers, so that more accurate dates might be obtained. However the work is still in the stage of growth.

Pollen Analysis:  As microscopic techniques became more refined, and as an increasing number of organic materials were microscopically analyzed, the researchers began identifying pollen grains embedded in these materials that might range from dried up varnishes up to woven clothes. Pollen analysis which led to relative dating was first done by the Swedish geologist Von Post around 1916.

Since that time many other researchers have analyzed samples of known and unknown origins and dates, and have made extensive charts about pollen distribution.  Using such pollen diagrams, information can be obtained about vegetation, floristic and climatic changes, sea level variations,  etc. which took place in the past. The difference in amount of pollen in 1cc can tell about the condition of the forest which produced it. If the amount is small, it might have come from tundra whereas larger amounts might indicate forests with vegetation which depends on pollen or spore reproduction.

Surprisingly, the tiny grains of pollen are very resistant to external factors, and survive almost unchanged for millennia, preserving an accurate record of history. Thus in addition to the relative dates, the pollen analysis, study of vegetation history using the microfossils (pollen grain and spores of size 15-50 um), can give us useful information about the target area's condition in the present and past.

Thus once a pollen-containing sample is examined, and the types of pollen, along with their density is determined, it is checked against standard charts for that region to arrive at relative dates and other information. This is a highly useful method in spite of its relative nature.

Rate Of Accumulation:  Archeological finds in most places are in the form of layers, with each layer representing one particular group/time of habitation.  The topmost layer will be the youngest, and the successive layers below it will be older. The same will be the chronological pattern of the artifacts found, with the youngest one in the topmost layer and the oldest one in the layer at the bottom.

The depth of the debris/mud/other materials can give some idea of age, and on comparison the relative dates of the layers can be guessed to some degree. If there are mounds sufficiently close, and if some interdependence can be demonstrated, then the layers in one place can be compared to the other and more reliable relative dates can be fixed for both through cross-checking and comparison.  If coins, or artifacts are discovered that can be dated more precisely, this relative dating can be made more accurate.

Rate of accumulation, though relative, has an important role to play in developing the history of succession in any given mound with multiple layers. It needs to be used with caution, because often only less than ten percent of  a given large mound is excavated to expose layers. Second, intrusion of one layer into another is common where there has been digging by men or animals. The researchers needs to be careful to choose an area where this has not happened.

Seriation:   This technique depends upon ceramics discovered from a given site. It has the advantage in that one does not need to know from which layer the ceramic came. For this kind of dating, the investigator takes all the available ceramics from a given place, and arranges them in a sequence that produces the most consistent pattering of that culture. This arrangement takes shape, technique, and usage-patterns of the ceramics to arrive at the relative chronology.

Ceramic artifacts all over the world have undergone change in shape, size, and manufacturing technology in a predictable pattern that has been understood relatively well due to the exceptionally large sample of ceramics discovered in situ for the last 150 years.

Among relative dating methods this has been a highly reliable method, used from the nineteenth century onwards, and has contributed much to the understanding of the relative dates of various cultures.

Varve Analysis:  Sediments are deposited by the rain/water cycle in many places. A type of these deposits is known as "varve". Counting the number of varves can give some idea of the relative age of a previously inhabited location and, by implication, of the culture. This techniques was developed by the Swedish scientist Baron de Geer in 1878, and has been refined further since then.  Audio-visual equipment and computers are now used to make the counting accurate.

A varve is made up of two layers: a thick light colored layer of slit and a fine sand layer. These layers are sufficiently distinct from each other to be counted.   Once the varve profile of a place is prepared, it can be compared with profiles in nearby area for cross-matching, and comparing of chronologies.

Varve-formation is  affected by a number of factors, and therefore it provided only relative ages, and a strict numerical accuracy is not possible.

Summary: One needs absolute dating techniques for developing a reliable and numerically accurate chronology in archeology, but often absolute dating techniques are more difficult and not available. Thus the importance of relative dating. In spite of this weakness, it is amazing the substantial increase in chronological understanding that has come with the help of relative dating techniques.

Absolute Dating Techniques

The following are the more important Absolute Dating techniques used in archeology:

Archeomagnetism:  Everyone knows that the earth has a magnetic field, and that this field is bound to create some effect upon things on the earth. It has been discovered that this magnetic field definitely affects materials, and even leaves an "imprint" on many of them. Using suitable equipment, that imprint can be discovered.

It has also been found via careful observations over the last four centuries, that the earth's magnetic field varies from time to time and place to place. The intensity (strength) and direction of the field are two factors that show significant variation.  Charts have been made of such variation for different places, and for different eras.  Once the magnetic factors of a new artifacts is determined, it can be compared with the magnetic charts for the location it was found, and its age can be determined with accuracy.

If no charts are available, the result would give a relative dating. But with scientists working in many fields around the world interested in archeomagnetism, Master Charts are being made and improved continually.  This in turn makes the absolute as well as relative dating more accurate.

Magnetic materials, especially if they were melted and cooled in the ancient world, record the orientation and strength of the magnetic field accurately. On obtaining such material, often from hearths, their orientation in relation to the current North Pole is recorded accurately. Then they are removed, and studied for the direction recorded in them, and also the strength of the field. In this manner reasonable accurate dating can be obtained for the entire period of human habitation of the earth.

Astronomical Dating: Astronomy is one of the most exact sciences, and astronomical dates of ancient events such as solar and lunar eclipse can today be calculated with precision. On the other hand, if any of the ancient records mentions such an event, its date can be calculated with unusual precision. Similarly, the date of construction of astronomically aligned buildings can also be calculated with accuracy, because with changes in earth's imaginary axis, the alignments are changing, providing a scale to determine dates.

Tables of known eclipses and their dates, tables of known angles and their dates, etc have been tabulated in great detail. Missing information can be filled in with great accuracy because here we are dealing with astronomical information that can be calculated precisely. Once available astronomical information from an archeological finding is compared with these tables, dates are known with a level of accuracy that will meet the strict demands of modern scientific investigation.

Dendrochronology: Many kinds of trees show somewhat concentric rings when cut across, polished and examined under microscopes. Generally these trees add one ring per year, though on rare occasions they can add more than one or none at all. However, since addition of one ring per year is the common behavior, these rings found on trees or their remains from archeological sites furnishes investigators with a very useful scale for determining time.

Tree-ring Example

Over the years investigators have studied a large number of samples, of many varieties of trees, originating in a number  of places, and spread over almost 5000 years. There is an attempt to extend the range, but the paucity of materials and other problems have made it difficult to obtain reliable dates beyond 5000 years BPE [before the present era].

Bristlecone Pines found in parts of America have provided a good amount of primary data to establish the calendar because these trees are able to survive the assault of the elements of nature for thousands of years. There has been much comparison and cross checking to solve the problem of multiple rings and missing rings.

The calendar is not as accurate as the Astronomical Dating system, but is sufficiently objective to date archeological discoveries with fascinating accuracy.  Thus remains of trees from archeological sites are carefully cleaned, sliced, rings examined and compared, and reasonably accurate dates are established. Much work yet remains to be done, but what has already been done is extremely helpful in coming up with good results.

Electron Spin Resonance:  There are random radiations all around, and electrons are liberated from atoms when they strike matter. In certain kinds of crystals these free electrons are trapped, and one can detect them using the method of ESR.

The older the sample, the larger will be the number of electrons trapped. Using samples of known age, extensive charts and lists have been compiled and standardized. Using this method, ages of a large number of quartz samples, fossilized teeth, flint, calcium carbonate in limestone, coral, and egg shells have been determined.

ESR Equipment

ESR dating has a very special advantage over many other methods in that it is non-destructive. Methods such as Thermoluminiscence and Opacity Stimulated Luminescence destroy the sample when it is dated. Thus there is no scope for retesting the sample. ESR, on the other hand, leaves the sample as it is, and the experiment can be repeated any number of times, giving a greater chance to eliminate experimental error.

Fission Track Dating:   This is a radioactive dating method, used in archeology to determine the ages of artifacts that contain uranium-bearing materials.

The atoms of many elements with high atomic weight, such as Uranium and Radium, break down spontaneously and this phenomenon is called Radioactivity.  The breakdown is also called fission. This fission produces two particles [alpha, beta] and an electromagnetic radiation [gamma]. The product of fission knock down electrons, and produce ionization in a series when they pass through substances. Using special techniques, these paths can be seen as tracks, called "fission tracks".  Obviously, the older a sample is, the greater would be the number of fission-tracks in it.

Natural and manufactured glass, stones used in hearths and in heating, and fired ceramics and tiles. They start with zero fission tracks at the time they are formed, and accumulate tracks in proportion to their age.  Using special methods, these tracks are then detected, counted and the age is determined.

Opacity Stimulation Luminescence:   Many minerals within sediments release electrons when they are exposed to certain kinds of light waves. When the number of electrons in a given sample, after exposing them to suitable kind of light,  are compared with the number in a sample of known age, the age of the first sample can be determined.

OSL is suitable for more recent samples that have been deposited by silty and sandy sediments, glacial deposits, etc. that have never been heated, and which have not had much exposure to light. This is a more recent dating method, and is still undergoing refinement and calibration, but is already yielding good results.

OxidizableCarbon Ratio:  Less accurate than the methods discussed previously, it is still one of the more useful methods of absolute dating. The method depends upon Humus and Charcoal, that are gradually oxidized but only slowly and in a strictly predictable manner.

Thus when suitable samples are discovered, the ratio of carbon left with oxidizable carbon is found out and compared with calibrated charts to find out dates. This method can be used not only to find the ages of individual finds, but also to establish the age-relationship of many biological objects.

OCR and Radio Carbon methods have also been compared carefully, giving greater accuracy to OCR, and this method of dating has therefore become quite common.

Racemization:  This technique is used to find ages of things that had an organic origin [humans, animals, plants]. All organic life has Amino Acids as its constituent. These acids are of two type, the L and D.

All living organisms essentially have the L type amino acids, which begin to change to D type after they die. This is known as racemization, and it the rate at which this happens is known accurately. Thus the level of racemization in a given sample can be compared with calibrated charts to find when the particular sample died.  This method can be applied to human and animal bones, teeth, plants, ostrich egg shells, mollusks, marine sediments, freshwater and marine shells, oyster shells, carbonate shells, calcareous sediments, and peats.

Some care is required because rate of racemization is affected by temperature. Thus though this is a method of absolute dating, it needs to be used in conjunction with other methods.

Thermoluminescence: This is a method of absolute dating, but still in a state of development. All natural materials are exposed to natural radiation, which dislodges electrons from the materials. Most of these electrons recombine with atoms, but a few of them remain trapped in locations that are known in solid-state physics as "imperfections". Heating of these samples releases these electrons, which produce a certain kind of light on doing so.

The method is used for dating ceramics, cooking hearths, rocks lying in hearths, and rocks that have deliberately been heated [such as flint or chert, a silica rich crystal]. Materials made of quarts, feldspar, diamond and calcite also lend themselves to this method of dating.

Radio Carbon Dating:  There is practically none who has not heard of this method. So important has this discovery been that WF Libby was given the Nobel Prize for it.

Carbon is a stable element with an atomic weight of 12. However, a small amount of carbon with the atomic weight of 14 is produced in the atmosphere due to cosmic ray bombardment. C14 is radioactive, and decays at a known rate. All air-breathing organisms have a definite C12, C14 ratio in their bodies. However, once they die, the amount of C14 begins to decrease due to radioactive breakdown. Thus if we can determine the ratio of C12 to C14 in an organic sample, one can compare it with calibrated charts and find the age when that organism died [or when the tree was cut down].

A Mass-spectrometer Used In Radiocarbon Dating

Radio-carbon dating gives highly precise dates in samples upto 5000 years BPE, and unreliable dates in samples older than that. The methods gives erroneous results in those samples which have an abnormally low or high accumulation of C14, but with increasing investigations and calibrations such abnormal cases can be ruled out in most cases.

Radio Carbon dating has turned out to be the most helpful and accurate method of dating in discoveries that yield organic samples. Archeology would never have been the same were it not for Radio Carbon Dating.

Summary: Dating or date-determination is both a science as well as art which can give excellent results if all the available data and determination-methods are correlated carefully. Such work has helped archeologist to correlated ages of artifacts with history and such correlation has given gratifying results for those who study Biblical archeology.

Table of Contents

Biblical Archeology, Volume 2 Dating Techniques in Archeology: An Intro

Dr. Johnson C. Philip Dr. Saneesh Cherian

Introduction

Initial Problems Faced In Dating:

Development Of Dating In Archeology

Dating Techniques Used By Archeologists

Introduction To Relative Dating Methods

Cultural Affiliation Dating:

Cation Ratio Dating:

Fluorine Dating:

Obsidian Hydration Dating:

Patination Dating:

Pollen Analysis:

Rate Of Accumulation:

Seriation:

Varve Analysis:

Absolute Dating Techniques

Archeomagnetism:

Astronomical Dating:

Dendrochronology:

Electron Spin Resonance:

Fission Track Dating:

Opacity Stimulation Luminescence:

Oxidizable Carbon Ratio:

Racemization:

Thermoluminescence:

Radio Carbon Dating: