11. Principles of stratigraphic analysis

Giorgio Buccellati – August 2009, June 2024

Introduction

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. 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. In point of fact, the situation is generally more complex, and, even more importantly, one must more sharply differentiate the two constitutive and very different aspects of stratigraphy, emplacement and deposition.

These two aspects interact with each other as, respectively, the static and the dynamic moments of one and the same situation. Emplacement is static in that it refers to the collocation of things in the ground. Deposition is dynamic in that it refers to the process whereby such collocation has come into existence.

Another fundamental aspect pertains to the way in which correlations can be established to an absolute space and time. We can accordingly dimension things as they are placed in measurable volumes (volumetry) or as their reciprocal and cumulative impact establishes a chain of events (sequencing).

The following chart summarizes the relative aspects of emplacement and deposition on the one hand, and of volumetry and sequencing on the other (the numbers refer to the order in which they are treated below):

	*static*	*dynamic*
*descriptive*	1. emplacement: internal characteristics and reciprocal contacts of things as they are in the ground.	3. deposition: inferences about how things have come to be placed where they are.
*dimensioning*	2. volumetry: metric measurements of things in space.	4. chronometry: relative intervals in time.

A full discussion of the concept of stratigraphy as used in the Urkesh Global Record is found in Chapter 5 of the Grammar (cf. also the companion website CAR). Here, only a few key points are summarized to help understand the presentation of the data.

Contact

The notion of contact presupposes the identification of discrete entities, the elements. The contact is not mere juxtaposition. From various factors, such as texture, alignment of components, organization of planes and volumes, etc., we may plausibly argue for different types of contact. In other words, the clustering is hierarchical, and supports the basic inferences about the depositional process that is to be assumed.

Clustering

Stratigraphic clustering refers to the way in which elements in contact, in the physical space, can be linked so as to denote temporal sequences.

The physical contact is what can in fact be observed and documented. As such it is the starting point of all archaeological analysis. The individual instances of contact are defined as part of emplacement, and are measured as part of volumetry. What lies beyond is the clustering of these points of contacts into groupings that subsume all the pertinent primary observations. From this we derive, in a properly arguable fashion, the depositional process and the overall sequencing.

Space/time

That space can be translated into time is the basic postulate that underlies the inferential process. For instance, having distinguished (through emplacement) two vertical planes as a cut vs. a face (texture, alignment, hardness, etc.), we may argue that a face is contemporary with the element behind it, whereas a cut is subsequent to it.

Strata

The notion of clustering finds its prime realization in the concept of stratum. This is a cluster of elements arranged according to the type of contact, and sorted according to nesting criteria that result in discrete wholes. These wholes are defined by the congruence of the elements in contact (e.g., a series of pits cut into a single accumulation), and by broad elements that extend to an entire volumetric unit (e.g., a floor that covers the entire surface of a locus).

There are three types of contact:

direct – physical contact between elements
indirect – contact mediated by a a third element (e. g., two floors on either side of a wall)
inferential – contact implied by the consonance of various factors, including typological analysis, across larger excavation areas (e. g. elements across several squares within the same unit).

For a detailed example see for now this file.

Integrative analysis

Phases and horizons extend the notion of clustering beyond the sphere of contact, reliying on typological and chronolgoical criteria. They are, in effect, non-contact clusterings of contact based clusters (the latter being represented by the strata).