302- STRATIFICATION PRINCIPLES
STRATIGRAPHY
Stratigraphy video
Stratigraphy is the study of strata or different layers in any site.
Stratigraphy practical demonstration
Principle of stratigraphy :
Archaeological stratigraphy is based on a number of axiomatic principles or laws, derived from the principles of stratigraphy in geology but have been adapted to meet the need of assessing the archaeological data. Some of its laws are hereunder :
1. Principle of superposition : According to this principle, in a series of layers, the upper most stratum is youngest and the lower most stratum is oldest unless the sequence has been overturned. since layers have been formed by depositing over each other for a long period of time.
2. Principle of relative dating : According to this principle, The time of layers can be no older than the age of the most recent artefact discovered with in them. That means the artefact found in the layer will can not be of later period than the deposition itself. This principle is quite useful in relative dating of the layer using artefact typologies and It is analogous to the geological principle of faunal succession.
3. The principle of original horizontality : in this law any archaeological layer deposited in an unconsolidated form will tend towards a horizontal deposition. the strata will always form in pre-existing basin of deposition.
Benefits of Stratigraphy analysis:
Stratigraphy is very beneficial in dating the layers : Incase the upper and lower layers date range is known then the date range of middle layer can also be reached at.
It is common knowledge that the lowest layer in a site represents the earliest occupation and the top-most layer the latest occupation. The human occupation of a site normally results in accumulation of one kind or the other.
Buildings crumble and new ones are built on the ruins. Objects lost or discarded get embedded in the earth. A flood may destroy a town and deposit a layer of alluvium.
Stratigraphical method of excavation is a surest method of determining the order of succession of events and cultures in a given site. The method implies the recognition of habitation layers during the excavation, so as to determine their sequence of formation. Thus stratigraphical excavation means, excavation layer by layer, keeping all the artifacts from each deposit in separate groups.
Procedure involves in Stratigraphic excavations :
The procedure is achieved by peeling off the successive strata first in control pit and then spread in entire trench. This procedure is repeated for every layer, thus pricisely following reverse order of deposition.
The identification of different layers in a habitation deposit is a difficult process requiring expertise, experience and commonsense. The colour, content, texture and compactness of different layers should be observed carefully.
A)MARKING LAYERS: As the excavation proceeds different layers of deposit are encountered. The variations in the deposit should be identified and distinguished by drawing a line along the layer with a knife. A layer may not run straight. Hence, the line drawn should follow all the ups and downs of the layer. Each layer thus separated is assigned a layer number running serially from top to bottom in serial numers (1,2,3,4).
D)STRATIGRAPHY AND DATING: Stratigraphy helps a great deal in dating the various finds and structures encountered in an excavation. During the excavation, all the time we may not be lucky to find datable objects like coins, inscriptions, etc. the problem becomes more complicated while dealing with prehistoric and protohistoric sites as we do not have coins and inscriptions to date firmly the different layers.
It is general observation that the bottom layers in a site are the earliest and the topmost layers the latest. So, depending on this principle we can date relatively a layer and with it the associated finds with reasonable accuracy. If fortunately, we find a datable object like coin, or inscribed article in a layer, that layer can be assigned the date suggested by that find. Consequently, the layer below this level can be dated to earlier period and the layers above can be dated to later periods.
In practice coins, inscribed slabs, copper-plate grants, inscribed pottery, Roman amphorae, NBP, PGW, Mauryan polish and various other objects have helped in dating particular layers and subsequently the other layers as well.
E)DISTURBANCE TO THE STRATA: There are many factors which cause disturbance to the strata, which have to be recognized by the excavator. Any refuse or storage pit may cut the earlier deposits. The articles found in this pit have to be dated to the period in which the pit has its origin or the layer which is sealing it. Similarly, post holes and robber-trenches also disturb the strata. In this case also care should be taken to demarcate such disturbances.
Stratigraphy is an important tool for identifying various periods and in reconstructing chronology. In fact the success of excavations largely depends on how carefully we observe the Stratigraphy.
Archaeological stratigraphy is based on a number of axiomatic principles or laws, derived from the principles of stratigraphy in geology but have been adapted to meet the need of assessing the archaeological data. Some of its laws are hereunder :
1. Principle of superposition : According to this principle, in a series of layers, the upper most stratum is youngest and the lower most stratum is oldest unless the sequence has been overturned. since layers have been formed by depositing over each other for a long period of time.
2. Principle of relative dating : According to this principle, The time of layers can be no older than the age of the most recent artefact discovered with in them. That means the artefact found in the layer will can not be of later period than the deposition itself. This principle is quite useful in relative dating of the layer using artefact typologies and It is analogous to the geological principle of faunal succession.
3. The principle of original horizontality : in this law any archaeological layer deposited in an unconsolidated form will tend towards a horizontal deposition. the strata will always form in pre-existing basin of deposition.
Benefits of Stratigraphy analysis:
Stratigraphy is very beneficial in dating the layers : Incase the upper and lower layers date range is known then the date range of middle layer can also be reached at.
It is common knowledge that the lowest layer in a site represents the earliest occupation and the top-most layer the latest occupation. The human occupation of a site normally results in accumulation of one kind or the other.
Buildings crumble and new ones are built on the ruins. Objects lost or discarded get embedded in the earth. A flood may destroy a town and deposit a layer of alluvium.
Stratigraphical method of excavation is a surest method of determining the order of succession of events and cultures in a given site. The method implies the recognition of habitation layers during the excavation, so as to determine their sequence of formation. Thus stratigraphical excavation means, excavation layer by layer, keeping all the artifacts from each deposit in separate groups.
Procedure involves in Stratigraphic excavations :
The procedure is achieved by peeling off the successive strata first in control pit and then spread in entire trench. This procedure is repeated for every layer, thus pricisely following reverse order of deposition.
The identification of different layers in a habitation deposit is a difficult process requiring expertise, experience and commonsense. The colour, content, texture and compactness of different layers should be observed carefully.
A)MARKING LAYERS: As the excavation proceeds different layers of deposit are encountered. The variations in the deposit should be identified and distinguished by drawing a line along the layer with a knife. A layer may not run straight. Hence, the line drawn should follow all the ups and downs of the layer. Each layer thus separated is assigned a layer number running serially from top to bottom in serial numers (1,2,3,4).
 |
| This section drawing,
made by Mortimer Wheeler in 1934, is one of the earliest to contain
'layer numbers' (from Wheeler 1943: fig. 10; courtesy of the Society of
Antiquaries of London). |
B)CULTURAL SEQUENCING: the different layers identified, as representing different cultural period, the layers are assigned cultural denotations starting from bottom to top, and marked in Roman numerals (I, II, III, IV).
Therefore, the layer numbers run from top to bottom, whereas the cultural period assignments run from bottom to top. If sub-periods are identified within a single period, they are denoted by English alphabets (A, B, C,).
C)RECORDING OF STRATIGRAPHY: The various layers identified in the excavation and their contents should be recorded properly for future reference and Report preparation. To distinguish the composition of the different layers and the contents thereof, different symbols are used to prepare sectional drawings, which present an unambiguous picture before the reader of an excavation report. For the purpose the following symbols are used in the section drawings:
D)STRATIGRAPHY AND DATING: Stratigraphy helps a great deal in dating the various finds and structures encountered in an excavation. During the excavation, all the time we may not be lucky to find datable objects like coins, inscriptions, etc. the problem becomes more complicated while dealing with prehistoric and protohistoric sites as we do not have coins and inscriptions to date firmly the different layers.
It is general observation that the bottom layers in a site are the earliest and the topmost layers the latest. So, depending on this principle we can date relatively a layer and with it the associated finds with reasonable accuracy. If fortunately, we find a datable object like coin, or inscribed article in a layer, that layer can be assigned the date suggested by that find. Consequently, the layer below this level can be dated to earlier period and the layers above can be dated to later periods.
In practice coins, inscribed slabs, copper-plate grants, inscribed pottery, Roman amphorae, NBP, PGW, Mauryan polish and various other objects have helped in dating particular layers and subsequently the other layers as well.
E)DISTURBANCE TO THE STRATA: There are many factors which cause disturbance to the strata, which have to be recognized by the excavator. Any refuse or storage pit may cut the earlier deposits. The articles found in this pit have to be dated to the period in which the pit has its origin or the layer which is sealing it. Similarly, post holes and robber-trenches also disturb the strata. In this case also care should be taken to demarcate such disturbances.
Stratigraphy is an important tool for identifying various periods and in reconstructing chronology. In fact the success of excavations largely depends on how carefully we observe the Stratigraphy.
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