Stratigraphy and Stratigraphic Analysis

In principle, stratigraphic analysis is the study of the deposits at an archaeological site. The word ‘stratigraphy’ itself is a modern compound linking a Latin term (which may be understood here as relating to ‘layers’) with a Greek term (which may be understood here as relating to the recording of such material); the etymology implies that ‘stratigraphy’ is the documentation and thus differs from the ‘stratification’ which is the material thus ‘recorded’, but like geologists, archaeologists frequently refer to ‘stratigraphy’ as being synonymous with ‘stratification’ (i. e., confusing the records with the actual sequence of layers visible on the edge of an excavation as opposed to the drawing of the section). Thus, in practice if not in principle, ‘stratigraphic analysis’ should be understood as being more interpretive and ‘stratigraphy’ more graphic, descriptive, or analytical; both aspects will be treated here as components of ‘stratigraphy’.

In practice, for archaeology today, stratigraphy is viewed as a matter of ‘sequencing’. These sequences are generally viewed as being of chronological importance, although it is recognized that the content of the layers can also provide information about climate, construction techniques, and the use of the site.

Broadly speaking, ‘archaeology’ is the study of the material culture and traces left by mankind, with a view to understanding the human experience; ‘stratigraphy’ is one of the two fundamental and specifically archaeological tools, the other being ‘typology’, the study of artifacts and types. Common to both stratigraphy and typology is that their subject matters (layers, objects) are not only the means by which archaeology approaches its human subjects, but are themselves the products of human activity. In this sense, both stratigraphy and typology differ fundamentally from their geological and biological counterparts, where the phenomena (geological formations, living creatures) being classified are not intentionally created by the very subject of the study.

As archaeological tools, the two should complement each other, with typological analysis pursued separately from stratigraphic analysis. Stratigraphic analysis should be used exclusively with respect to the analysis of the deposits and the sequence of deposits at an archaeological site. Typological analysis should be applied to the artifacts and monuments. Both should contribute independently to the conclusions of archaeological work.

Stratigraphic analysis allows the excavator to gain access to decisive information about the formation, use, and relative chronological sequence of an archaeological site. In the publication of archaeological excavations, it is ultimately this analysis which is the basis of the interpretation of the architectural history, the context of individual small finds, and the arguments about dating, etc. Thus only the correct identification of stratigraphic units ‘during the excavation’ can assure that the ‘published’ analysis of the finds is assured sufficient material support for argumentation.

Thus, in principle, (1) the analysis of stratigraphic deposits during the excavation should serve to guide excavations by endeavoring to follow and excavate stratigraphic units, and (2) the analysis of the stratigraphic records made during the excavation should be the point of departure for the interpretation of the excavation. However, the analysis of the stratigraphy is usually associated with chronology and sequences rather than architecture, etc.

Less Technically Correct Utilization of ‘Stratigraphy’

There are two other fashions in which archaeologists use the term ‘stratigraphy’ which are strictly speaking incorrect, but the logical result of the understanding of ‘stratigraphy’ as merely a variant of ‘chronology’: so-called ‘horizontal stratigraphy’ and so-called ‘reversed stratigraphy’.

In general, ‘horizontal stratigraphy’ is used to describe the chronological development of a cemetery (or similar arrangements where a series of similar structures are spread across a site) whereby the earliest tombs are located in one area and the latest in another, and a gradual spreading of the cemetery can be followed between the two areas. Occasionally, later tombs are actually sunk into earlier tombs and thus the sequence is clear - but it is equally evident that this is ‘stratigraphy’ in the sense of ‘the superposition of layers’ and thus ‘stratigraphy’ in the sense understood in this article.

Usually, however, the use of the term ‘horizontal stratigraphy’ is related to the means of identifying the development of the cemetery based upon the typological analysis of the offerings in the tombs: the offerings are assigned relative chronological dates and the spread of the cemetery thus established in chronological terms. In fact, therefore, ‘horizontal stratigraphy’ refers to a procedure which is exactly the opposite of stratigraphy in terms of depositional layering, since stratigraphic analysis refers to the study of the sequence of layers more or less independently of the objects. The study of the objects and their interpretation is ‘typology’. In principle, conclusions based upon stratigraphic analysis should play a role in attributing dates to objects; the use of the typological analysis of the objects alone to determine chronological relations and development of sites is not stratigraphic analysis, but rather typology. (However, the term ‘horizontal stratigraphy’ is so widespread that there is no reason to dispense with it; one must merely view it as a chronological rather than a stratigraphic tool.)

Technically equally incorrect is the term ‘reversed stratigraphy’, which is based upon the same conceptual understanding of stratigraphy as a means of studying chronological sequences via typological analysis. The term is usually used to refer to the situation in which the most recent overlying material is at the base of a deposit and the earliest material at the top of the deposit, as, for example, in the spoil heaps from an excavation (either due to construction or to an archaeological excavation). In fact, of course, the sequence of the deposition of the layers is chronologically correct in that the deposition of the lowest layer preceded the deposition of the highest. Usually the character of the deposit is betrayed by the presence of older objects in upper levels and younger objects in lower levels, and thus the chronological interpretation is based upon the typological analysis of the objects rather than the stratigraphic sequence. In general, the typological analysis leads to a detailed review of the stratigraphic sequence and the recognition of the fact that the deposit consists of reworked archaeological deposits. In theory, it would be better if an analysis of the stratigraphic deposits were to lead to the recognition of the situation immediately, but it must be stressed that the stratigraphic sequence is not always as clear cut as one would wish, hence the need to study the stratigraphy constantly.

Levels of Stratigraphic Analysis

Stratigraphic analysis in archaeology involves four distinctly different activities. Two of these are related to excavation in the field, two to publications and debate.

The first, primarily geological-pedological but also architectural, is the analysis of deposits as related to the processes of site formation (see Sites: Formation Processes). The second, primarily artifact-typological, is the identification of deposits with the object of specifying the origin of the objects recovered in an archaeological excavation.

The first of these goals depends upon the identification of the deposits in geological or pedological terms. The second depends upon relating such deposits to the units employed in an excavation. The two must always be done in conjunction, yet the difficulties of stratigraphic analysis in archaeology arise primarily because it is impossible to excavate in units which invariably correspond exactly to the stratigraphic deposits. This obstacle is compounded by the fact that it is frequently impossible to actually recognize and classify the deposits correctly during the excavation.

Unfortunately, however, the success of an archaeological excavation depends upon the mastery of the stratigraphic sequences and the publication of the results in a scientifically compelling fashion, since only the published results are available to other scholars.

The third, analytical and interpretive, is precisely the presentation of the sequences and the arguments in the publication of the excavation. The fourth, interpretive and polemic, involves the incorporation of the stratigraphic sequences in the interpretations of historical events and developments, chronological reconstructions, and the discussion of artifact types in larger comparative frameworks.

Any argument about the results of an excavation usually ultimately centers on the interpretation of the stratigraphic relations. Even an impeccable presentation of results can lead to a dispute if there is disagreement about the interpretation. Such disagreements can range from details such as the context of a find (e. g., the relative value of a find in primary context, in situ on a floor, as opposed to a tertiary context such as ‘fill’) to the identification of artifact classes used to provide a chronological framework (e. g., Perigordian points).

Thus stratigraphic analysis in the field is of equal importance to correct and speedy publication (and very frequently the publication of excavation reports is delayed due to inadequate stratigraphic observation and recording during excavation).