Stratification (archeology)
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In archaeology, especially in the course of excavation, stratification is a paramount and base concept. It is largely based on the Law of Superposition. When archaeological finds are below the surface of the ground (as is most commonly the case), the identification of the context of each find is vital to enable the archaeologist to draw conclusions about the site and the nature and date of its occupation. It is the archaeologist's role to attempt to discover what contexts exist and how they came to be created. Archeological stratification or sequence is the dynamic superimpostion of single units of stratigraphy or contexts. contexts are single events or actions that leave discreet detectable traces in the archaeological sequence or stratigraphy, these can be deposits such as the back-fill of a ditch, structures such as walls and "zero thickness surfaciques" better know as "cuts". Cuts represent actions that remove other solid contexts such as; fills, deposits and walls, an example would be a ditch "cut" through earlier deposits. Stratigraphic relationships are the relationships created between contexts in time representing the chronological order they were created, an example would be a ditch and the back-fill of said ditch. the relationship of "the fill" context to the ditch "cut" context is "the fill" occurred later in the sequence, you have to dig a ditch first before you can back-fill it. A relationship that is later in the sequence is sometimes refereed to as "higher" in the sequence and a relationship that is earlier "lower" though the term higher or lower does not itself imply a context needs to be physically higher or lower. It is more useful to think of the higher term as it relates to the contexts position in a Harris matrix which is a two dimensional representation of a sites formation in space and time.
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[edit] Principles or "laws" of archaeological stratigraphy
The Law of Superposition In a series of layers and interfacial features, as originally created, the upper units of stratification are younger and the lower are older, for each must have been deposited on, or created by the removal of, a pre-existing mass of archaeological stratification.
Law of Original Horizontal Any archaeological layer deposited in an unconsolidated form will tend towards a horizontal disposition. Strata which are found with tilted surfaces were so originally deposited, or lie in conformity with the contours of a pre-existing basin of deposition.
Law of Original Continuity Any archaeological deposit, as originally laid down, will be bounded by the edge of the basin of deposition, or will thin down to a feather edge. Therefore, if any edge of the deposit is exposed in a vertical plane view, a part of its original extent must have been removed by excavation or erosion: its continuity must be sought, or its absence explained.
Law of Stratigraphic Succession Any given unit of archaeological stratification takes its place in the stratigraphic sequence of a site from its position between the undermost of all units which lie above it and the uppermost of all those units which lie below it and with which it has a physical contact, all other superpositional relationships being regarded as redundant.
[edit] Combining stratigraphic contexts for interpretation
Understanding a site in modern archaeology is a process of grouping single contexts together in ever larger groups by virtue of their relationships. The terminology of these larger clusters varies depending on practitioner but the terms interface, sub-group and group are common. An example of a sub-groups could be the three contexts that make up a burial; the grave cut, the body and the back-filled earth on top of the body. in turn sub-groups can be clustered together with other sub groups by virtue of there stratigraphic relationship to form groups which in turn form "phases". A sub-group burial could cluster with other sub groups burials to form a cemetery which in turn could be clustered with a building such as church to produce a " phase". Phase is the most easily understood grouping for the layman as it implies a near contemporaneous Archaeological horizon representing "what you would see if you went back to time X". the production of phase interpretations is the first destination of stratigraphic interpretation and excavation. Digging "in phase" is not quite the same as phasing a site. Phasing a site represents reducing the site either in excavation or post excavation to contemporaneous horizons where as "digging in phase" is the process of stratigraphic removal of archaeological remains so as not to remove contexts that are earlier in time "lower in the sequence" than other contexts that have a latter physical stratigraphic relationship to them as defined by the law of superposition
[edit] See also
- Excavation
- Archaeological context
- Archaeological association
- Relationship (archaeology)
- Archaeological phase
- Reverse stratigraphy
[edit] References
- Harris, E. C. (1989) Principles of Archaeological Stratigraphy, 2nd Edition. Academic Press: London and San Diego. ISBN 0-12-326651-3el:Στρωματογραφία (αρχαιολογία)
