The concept

Giorgio Buccellati – August 2009, April 2026

Stratigraphy

The term “stratigraphy” is ubiquitous in archaeological discourse, but the concept is not generally as rigorously defined as one might wish. In a loose sense, it is often used to refer to a variety of concrete field situations where different elements overlay or intersect each other.

The concept originated in geology and has remained a core feature of this discipline, with a variety of methodological approaches having arisen in recent years. Catuneanu 2026 provides a comprehensive synthesis of eight distinctive types of geological stratigraphy, two of which are particularly relevant for archaeology.

Allostratigraphy (Catuneanu, chapter 8) focuses on the interface among the constitutive elements – the term “allo” in the name referring to the discontinuities and bounding surfaces that are found among, and are thus “other than,” the building blocks of the system, i. e., the lithological elements which can be defined morphologically. This correponds to the types of contact among elements in archaeological stratigraphy.
Sequence stratigraphy (Catuneanu, chapter 9) focuses on the dynamics of events as they can be assumed on the basis of repetitive conformities especially in their surfaces as evidence of erosion and deposition. This is the most recent trend in geological stratigraphy, whereas it has been at the center of archaeological stratigraphy since the beginning, particularly in its effort at relating space and time as part of the same continuum.

Interestingly, no substantive mention is generally made, in discussions of geological stratigraphy, of archaeological stratigraphy (see. e. g., Mardon 2021). In effect, the latter differs in its essence from geological stratigraphy, even though the starting point is the same. The difference is instructive, and it needs to be brought out. A comparison is certainly useful for archaeology, as one would think it should be for geology as well.

Geological vs. archaeological stratigraphy

Archaeological stratigraphic analysis differs in three respects from its geological counterpart, and it is a radical difference. What is at stake is both the nature of the data and the method of analysis.

Natural vs. cultural build-up

The dynamics of the formation processes as can be inferred from the record as found in the ground is altogether different. The geological record reflects relatively few natural processes that affect wide geographical areas, whereas the archaeological record reflects a multiplicity of cultural (and occasionally natural) events that affect well defined and generally well contained spaces.

In particular, cultural deposition presupposes both intentional and accidental events, and in the intentional events we can infer purpose and function.

The same and the unique

The geological record is built on sameness. A given lithological element, definable in terms of distinct characteristics, is the same at different points in the record, and this implies a regional or global tectonic event.

Archaeological stratigraphic analysis, on the other hand, is built around uniqueness. Each element, however minute, has a “dignity” of its own (Buccellati & Kelly-Buccellati 2026). This does not mean that there are no similar events that can have identical effects on elements, or that there are no similar phenomena to be identified in the record. Obvioulsy, excavation of a pit or the construction of a structure such as a wall are similar and hence “repetititve” – and so is a conical cup similar to hundreds of other conical cups found dispersed in the “strata” that have been deposited at a given site. But each event and each element must be viewed in and of itself, as specific and unique. Similarity is not sameness.

Singularity is thus a distinctive feature of the archaeological record, and we must always be mindful of the uniqueness of each and every element that is exposed. This is not to say that we cannot generalize. Chronological horizons and typological assemblages are examples of how concrete single elements presuppose wider ranges into which they may fit. But each element retains its own particularity and must be treated as such.

The index and the whole

Any given point that is exposed in the geological record is an index to a wider whole: a given sedimentary facies partly exposed at a given location serves as an index to both a larger whole (the full sedimentary deposit still unexposed) and to a given event that caused teh sediment to occur.

In the archaeological record, on the other hand, every single element is a whole in itself. As such, it needs to be seen first in its relationship to any other eement with which it is in contact, and second with the typological universe proepr top the culture from which it originates.

Emplacement and deposition

It is as a result of the considerations just made that archaeological stratigraphic analysis rests on the two cardinal principles of emplacement and deposition.

Emplacement gives us the precise record of the location of each and every element, no matter how minute. It is the point of repose of a dynamic process which caused the emplacement.

From this evidence, we can infer how these elements came to be where they are. The argument is built on the presupposition of function, use, accidents, but rests uniquely on the objective documentation of the types of contact evidenced by their emplacement.

Types of interaction

At its simplest, one thinks of layers that are horizontally placed one on top of the other, and a layer cake is the most commonly used metaphor for this situation. This is the principle of superposition, which is correct especially in a chronological sense (later events affect earlier ones after these have left elements in a certain “position”). Given the nature of the context, archaeological stratigraphy is highly distinctive. Later events often do not just cause elements to “lay” on top of earlier ones, in a layer-like fashion. They often intrude and disturb the earlier “layers” so that their original disposition is altered.

Another important factor is that the process, unlike what happens in geology, is non repetitive. Resulting from cultural activities, the depositional process is highly unpredictable, and must therefore be observed and recorded according to distinctive concepts and procedures – according to a distinctive, archaeological grammar.

At the basis of such a grammatical approach lies a sharp distinction between emplacement and deposition. One must observe and document each element as it is found in the ground in order to infer from it how it got there in the first place. To this we will turn our attention the following pages.

References

Burgess & al 2021

ChatGPT 2026-420

Cateneanu 2006, 2026

Gavin

Harris

Mardon & al. 2021 esp. p. 111f

Wikipedia: Stratigraphy; Stratigraphy_(archaeology)