Home > Archaeology, Pyla-Koutsopetria Archaeological Project, Survey Archaeology > A Comparison Between a Survey Assemblage and an Excavation Assemblage

A Comparison Between a Survey Assemblage and an Excavation Assemblage

For the past few months, David Pettegrew and I have been “publishing” the preliminary results of some experimental analysis conducted over the past year at the Pyla-Koutsopetria Archaeological Project on Cyprus.  As part of the experimental component to our project we were interested in documenting the relationship between the surface assemblage and the assemblage of material produced by excxavation

The archaeological fieldwork conducted on the elevated height of Vigla provided us with an opportunity to compare assemblages produced by intensive pedestrian survey and the excavation of a trench in the survey area.

Longstanding critiques of survey have suggested that the relationship between the surface assemblage and the subsurface material is too problematic for survey to be a technique used to produce a comprehensive view of the landscape. While it is true that there are more variables in the formation processes that impact the creation of a surface assemblage, we should be aware of the potential for a false dichotomy. Excavated assemblages are every bit as much a product of formation processes as those on the surface and as a result, we always have to temper our interpretation of past events with the understanding of the archaeological record as the product of a whole range of physical and cultural transformations. The goal of this comparison then is not to test the surface assemblage against the subsurface material, but rather to suggest that their correspondence indicates that the area may have endured similar archaeological processes.

As with all of our experimental units, the comparison is influenced by significant differences in the spatial comparison between the two sample areas. The surface area of our trench EU 8 represented only 6 sq meters; The two survey units 500 and 500.1 combined to covere over 6000 sq m. Any comparison of area, however, is problematic; the trench had volume and the relatively two-dimensional surface of the survey area did not.

SurveyAndExcavation  

The excavation unit produced significantly more ceramic material. The excavation unit produced over 4000 artifacts. By comparison, we counted anywhere from 366 to close to 1000 artifacts from our survey of various areas on the top of Vigla (depending on surface conditions and the number of walkers available), and these samples allowed us to estimate an overall artifact density of between 15,000 – 11,000 artifacts per ha. These are astronomical densities by any reckoning.

While we counted every artifact visible in our 20% sample of the surface, we collected artifacts using the chronotype sampling strategy which required us only to collect each unique type of sherd from each swath.  Using this technique in two campaigns of field walking on Vigla, we collected 963 artifacts with a weight of 27.6 kg.  In contrast, we collected and analyzed every artifact from the excavation area and this resulted in over 4000 artifacts, but this assemblage weighed less than 10 kgs more (37.0 kg) than the assemblage collected from survey.

The nature of the chronotype sampling method used in the survey makes it difficult to find a metric to compare the quantity of material collected from the survey against the quantity of material collected from excavated contexts. The key point for evaluating the correspondence between the two assemblages is not necessarily the quantities of material but rather the presence or absence of material indicating particular activity, periods, or material types present in the area.

Comparing the period date between the two collection strategies reveals that the survey collection produced more chronotype period categories (16 compared to 14) and nine of the periods represented in the survey assemblage were also represented in the excavation assemblage. In general, the survey material represented a longer chronological range with material from later periods present on the surface including material from the Late Roman, Medieval-Modern, and Modern periods. The excavated area, in contrast, produced more material from narrower periods and at least one object from a period earlier than those represented in the survey, a sherd potentially dating to the Bronze Age (for more on broad and narrow periods, see here). This artifact appears to pre-date the earliest phases of architecture present in our trenches and may not represent a past activity on the site. In general, the material from both the survey and the excavation overlap, but the excavation material offered slightly more chronological resolution than the material from the survey.

The diversity of chronological periods in the survey material would appear to extend to the chronotypes represented in each unit. The excavation produced 54 chronotypes, while the survey unit produced 57. There are 30 overlapping chronotypes between the two collection methods. While the different sampling techniques make it difficult to compare the assemblages in a meaningful way, the quantity of material from each area nevertheless provides a very basic matrix for comparing the relative quantity of various types of material from each unit. The survey and excavation both produce a significant number of artifacts from the three rather general chronotypes: ‘Coarse ware, ancient historic’, ‘medium coarse ware ancient historic’, ‘kitchen ware ancient historic’.  The excavation also produced a significant proportion of material from two additional chronotype that were poorly represented in the surface assemblage: ‘animal bone’ and ‘fineware, Hellenistic-Roman, Early’ which made up 6.6% and 5.5% of the excavated material respectively, but less than 1% of the material from the survey. The absence of animal bone on the surface of the ground could be an issue with visibility (white and tan bones do not stand out as well against the buff colored soil) and certainly preservation. 

It is notably harder to compare the potential range of activities present in the area. The chronotype method of collection privileges larger, better preserved sherds (walkers will often discard small or poorly preserved sherds if they find larger examples of the same chronotype). It also tends to under represent very common chronotypes in proportion to the total assemblage. In other words, there are fewer examples of chronotypes such as “medium coarse body sherd, ancient historic” in the survey sample in part because field walkers were instructed not collect multiple examples of this very common type of artifact. In the excavation, excavators collected every example of a “medium coarse body sherd ancient-historic” causing sherds of this type to make up a larger proportion of the total assemblage.

This tendency can be seen in the relative size of artifacts collected from the survey and excavation. From the survey, the collected artifacts were much larger and this probably reflects both our field walkers’ tendency to select larger sherds more frequently than smaller sherds for collection and the difficulty seeing the smallest sherds on the ground from a standing posture. These two tendencies combined to produce an average survey artifact weight almost 30 g as compared to the average size of an excavation sherd that was under 9 g.

The fabric groups present show some significant differences in the assemblage that we can largely trace to different sampling strategies. The survey unit preserved more coarse ware
(47%) whereas the majority of material from the excavated unit was medium coarse ware. The weight of the two fabric groups as a percent of the total assemblage sheds more light on the situation. Medium Coarse wares from the excavation represented 53% by volume, but only 22% of the assemblage by weight. In fact, the average weight of a medium coarse ware sherd is less than 4 grams. In other words, many of the medium coarse fragments of pottery from the excavation are quite small, and these sherds are the most likely to be overlooked during survey. Cooking/kitchen ware, coarse ware, and amphora represented the other significant parts of the excavation assemblage. As the chart below indicates the percentage of weight is significantly different from the proportions determined by counts. In weight amphora and coarse wares combine to make up the majority of material.

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The material from survey shows different proportion, but these proportions are significantly biased by our sampling technique that suppressed the collection of redundant artifacts.

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Coarse ware is the most common fabric group by quantity and makes up the majority of material by weight. Amphora sherds, which tended to be handles or very large body sherds, represent a massive quantity by weight, but significantly lower percentage by quantity. The opposite is true of medium coarse ware and kitchen/cooking ware.

Similar tendencies are visible from rim-base-handle-sherd analysis (for more on R-B-H-S Analysis, see here). 

image

The results of this comparison suggest that for the height of Vigla the most major differences between the assemblage produced by survey and that produced by excavation are tied to the different sampling strategies used in these different contexts. At the same time, the basic patterns present in the survey assemblage were also present in the assemblage from the excavation.  The presence of material from the Classical and Hellenistic period, the presence of fine ware, kitchen/cooking ware, and utility wares, and the almost complete absence of earlier material allows us to argue that the site was first occupied in the Archaic to Classical period, saw domestic activities, and then was used less intensively in later periods.  This close correlation of survey and excavation assemblages reflects, in part, the stability of the soils on Vigla and the relative lack of erosion, on the one hand, and the lack of intensive activity during later periods, on the other.  In other words, the surface assemblage and excavation assemblage enjoyed similar sets of formation processes which produced similar assemblages. 

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