Describing and Comparing Archaeological Spatial Structures Case Study Meymanat Abad

Traditionally, occupation phases, without clearly identifiable contexts, have been excavated according to arbitrarily defined vertical spits. The disadvantages of this approach are obvious—where occupation occurred on an undulating or sloped surface, stratigraphic levels or activity horizons, if they existed, are often unlikely to be identified and it becomes almost impossible to differentiate different phases of occupation within any period. Recently, three-dimensional recording of artefact locations with survey equipment, such as total stations, has become more common on these types of sites. In this paper, this method for recording and modeling stratigraphic relationships using 3D analysis a ”Arcmap” programs is applied.


Introduction
Interest in the analysis of patterns of spatial distribution of artifacts on prehistoric occupation floors has been growing rapidly in recent years. Virtually all archaeological examples of analysis of spatial patterns have been based upon inspection and impressionistic interpretation (de Lumley et al., 1969).
The methods used for excavating sites with few defined features or clear contexts have evolved with time, however they have tended to have at the basis of any method a "vertical spit" approach (Mellars, 1987). Sites are rarely excavated stratigraphically as, although phases of occupation may exist, apparent differences in context often prove to be geomorphologic in origin, or more commonly, clear differences in soil color or texture are not apparent. Given the problems with their definition, any stratigraphic (or rather sedimentological) levels are often left recorded only as sections, although their relationship to artefact distributions is obviously important. The disadvantages of this system are obvious. Unless the palaeosol was perfectly level, "intact" phases of occupation on a once sloped or undulating surface become separated into many different vertical "spits", and artefacts related to each other may never be associated (Figure 1).
In recent years, more and more attention has been focused on the retrieval and analysis of information from smaller scales within archaeological sites as it becomes easier to record artefacts at higher resolutions (and in three dimensions) with specialist survey equipment (Dibble & Lenoir, 1995).
However, the means of relating artefacts to potential stratigraphic levels (whether clearly visible or not) is far from straightforward (Harris & Lock, 1996). Significant progress has been made since the 1980s on visualizing three-dimensional relationships in excavations, such as using solid modeling techniques (Reilly & Shennan, 1989) or linking databases to graphics facilities (Reilly, Locker, & Shennan, 1988), an area of research made more feasible recently by developments in three-dimensional Computer Aided Design packages. Displaying three-dimensional relationships can be an important aid in understanding stratigraphical relationships and identifying potential patterning.
However the further step towards three-dimensional spatial analysis is proving a serious challenge. The need to develop a method for analyzing phasing on prehistoric sites has become more pressing, particularly with increasing interest in the subsequent occupation of particular sites. Identifying repeated occupation by human communities with similar technologies depends on differentiating phases of occupation on excavated sites. appears that, the site was deliberately damaged by bulldozers and ploughing, particularly on the eastern side. As a result of these site formation processes, it is particularly difficult to estimate how large Tepe Meymanatabad was before the recent damage, and this makes it virtually impossible to estimate how large the site was in antiquity. The site consists of two low mounds hereafter called northern mound and southern mound.

Operation at Trench 1 at Tepe Meymanatabad
Preliminary excavations at Tepe Meymanatabad were carried out in late summer of 2011. The initial aim of this excavation was to expose a stratigraphically defined sequence of occupation at the site, and when this was combined with the results of the excavations at Tepe Ghabrestan (Fazeli et al., 2005(Fazeli et al., , 2009Matthews & Fazeli 2004;Majidzadeh, 1976Majidzadeh, , 1981, it was hoped that this would provide a preliminary insight into the ceramic sequence and the occupational history of the Northern Central Iranian Plateau as a whole during the 4 th millennium B.C. Furthermore, an area of 5 m by 5 m at Tepe Meymanatabad, hereby called "Trench 1" was excavated. Excavation proceeded by the identification and removal of discretely stratified layers or "units", whether they were originally produced by natural deposition processes or as a result of human action. A unit can be any type of stratified deposit, such as pit fill, a wall, foundation material, floor surface, bench, hearth, collapse, fill, and wash etcetera.
During the excavation, each stratigraphic unit was referred to as a Locus, which was delimited, excavated separately, and allocated a sequential ID number, in this case, from 1001 to 1054. Each locus was recorded on a separate data sheet, where the nature of the deposit was characterized through the selection of a relevant tick-box and a written description. The location and extent of each locus was also drawn in plan, and absolute levels were taken so that it could be defined in three-dimensional space.

2011)
The small size of the sounding sometimes meant that individual deposits were excavated in a number of different parts, which were each allocated their own locus number, but which could be combined later. The stratigraphic relationships between each locus were also recorded, and the relationships for all of the deposits in the sounding are illustrated using a standard Harris matrix. After digitally recorded, all cultural artefacts, animal bone or carbonized material and pottery sherds recovered from a locus was placed in a clean plastic bag together with a separately bagged label marked with the date, site name, the trench number, the sequential locus number and a description of the type of object. Apparently associated with these artefacts were three occupation phases, dated to approximately 3400 to 3200 B.C based on pottery classification. Careful excavation began from 1052.993 m above the sea level. All artefacts with no exception-3699 artefacts in total-were individually numbered and recorded in three dimensions using a Total Station, TS02-7 and planned on recording sheets (Table 1).   (Table 2).  , 1137, 1139, 1142, 1150, 1197, 1198,1199, 1200, 1201, 1221, 1222, 1224, 1225, 1226, 1262, 1263, 1264, 1273, 1274 1138, 1140, 1141, 1143, 1144, 1145, 1146, 1147, 1148, 1151, 1152, 1154, 1155, 1156, 1271 1149, 1160, 1175, 1178, 1243, 1245, 1239, 1279,  The silt pan is likely to have formed after before the occupation initiated, its formation relating to the development of the peat. However (as is often observed) the undulations of this level were clearly related to the structure of the upper two surfaces. The spatial distribution of artefacts themselves and in relation to the features proved particularly interesting. The artefact re-fit patterns (shown in Figure 5) appeared to relate to distinctive activity patterns on the floor of the first occupation phase. The dimensions of the artefact concentrations accorded well within the first apparent level. An obvious query thus arose as to the integrity of site-in effect whether a coherent explanation could be put forward to explain the apparent distribution patterns, or whether in fact, post-depositional processes www.scholink.org/ojs/index.php/ac Archaeology and Culture Vol. 1, No. 1, 2018 had had a major influence on the distribution of artefacts, forming a chance association in the upper deposits. Since the upper levels at many of low mounds are often assumed to be fairly disturbed contexts, a site of this type with minimal post-depositional disturbance and a coherent "story" could be significant not only in the context of the specific activities which might be reconstructed, but also in terms of the potential for recovering other similar late Chalcolithic sites. One accepted method of assessing the integrity of these types of sites is to assess the vertical displacement of artefacts (Barton 1987). The vertical displacement of the finds from the 2010 season's excavations at Trench 1 is shown in (Figure 7 & 8). Points on each of the soil interfaces had been recorded as the area was excavated.

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First, the gridded points taken from each sediment interface was interpolated to produce three surfaces (see Figure 8) corresponding to the soil interfaces. The method used for this interpolation is essentially the same as that for modeling much larger scale landscape surfaces.  In this case, the points were entered into ArcInfo as a series of points used to form a TIN surface and interpolated using quantic interpolation to calculate a surface from which the z coordinates of any point could be determined. These surfaces (which had similar forms, although at different heights) provided a model of the shape of the past land surface, and as such a guide to the original relative locations of the artefacts. By calculating the vertical disturbance of each artefact from each of the surfaces (which would have been "parallel" to the past land surface) we can get a measure of the relative displacement from the past land surface on which they were deposited. This is done within GIS by "projecting" the artifacts onto each surface and subtracting the "projected" height from the actual excavated height.  We may assume that maximum vertical concentration of artefacts marks the past land surface on which they were deposited. Other lines of evidence also support the idea of a minimal vertical dispersal of www.scholink.org/ojs/index.php/ac Archaeology and Culture Vol. 1, No. 1, 2018 artefacts from the original land surface. Micro-debris analysis and micro-morphology studies revealed the same distribution patterns for micro-debris as shown for all finds above. Likewise the results of pollen concentration analysis at this site currently undertaken by Dr. Maghsudi from Tehran University demonstrated that pollen, spores and charcoal had not moved down the profile and become concentrated at the base of the deposits (Personal communications).

Zoshk, 2011)
In order to test the relative movement of different size classes of artefacts, the vertical distribution from the modeled stratigraphy of the largest size class-big Pottery sherds and bones-was considered separately. The mean difference in depth between the two classes was 0·006 m (89% CI); a t-test on the difference in the mean depth between the two classes gave P=0·711. As the confidence interval included 0 and the P value was very large it is safe to conclude that there is no significant difference between the two classes. A possible explanation for the minimal influence of post-depositional processes may lie in the timing of occupation of the site. If occupation occurred at the time of incipient www.scholink.org/ojs/index.php/ac Archaeology and Culture Vol. 1, No. 1, 2018 peat formation, the deposition of artefacts may have coincided with a low intensity of biological processes such as earthworm activity. It is clear that the GIS method used provides a "better" means of assessing disturbance than simply considering vertical heights (as shown in Figure 8). The results are particularly important in demonstrating the high integrity of the site, with apparently only a minimal influence of post-depositional processes in disturbing artefact locations, at least where the vertical movement of artefacts is concerned.

Result and Decoction
Careful excavation, three-dimensional recording and the use of GIS to model sedimentological levels jointly proved very valuable tools in the analysis of occupation phases at Tepe Meymanatabad. The results from the careful, albeit slow and painstaking excavation and three-dimensional recording of the site described above clearly justify the time involved in excavation. Whilst widely available and easy to use "truly three dimensional" programs for site analysis are still not available, we suggest that the GIS based method described above might provide a useful tool for the interpretation of many sites. It can provide a means of assessing the integrity of the site and the influence of post depositional processes where only a limited span of occupation has taken place, and the potential for identifying different phases of occupation where these phases are vertically separated. We recommend the use of this technique for most sites, at least as a preliminary study used before selecting an appropriate excavation method and look forward to seeing new applications and developments in this field.