GIS based interpolation applied to distinguishing occupation phases of early prehistoric sites P. Spikins, C. Conneller, H. Ayestaran and B. Scaife Abstract Traditionally sites occupied by mobile groups, without clearly identifiable contexts or phases, 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 with a memory store, such as total stations, has become more common on these types of sites. However, the excavation methods and means of interpretation needed to link this type of three-dimensional resolution with stratigraphic levels has been lacking, particularly as ‘true’ 3d programs are not widely available to deal with this type of information. In this paper, a possible method for recording and modelling stratigraphic relationships using typical ‘almost 3d’ GIS programs is described. Keywords: Geographical Information Systems (GIS), Interpolation, Stratigraphic Interpretation, Hunter-gatherer sites, Mesolithic Introduction The methods used for excavating sites with few defined features or clear contexts – typically those left by repeated occupations of mobile populations – have evolved with time, however they have tended to have at the basis of any method a ‘vertical spit’ approach (e.g. Mellars 1987, Healy et al. 1992, Mithen and Lake 1996). Sites are rarely excavated stratigraphically as, although phases of occupation may exist, apparent differences in context often prove to be geomorphological in origin, or more commonly, clear differences in soil colour or texture (aside perhaps from charcoal lenses) 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 (figure 1(a)), ‘intact’ phases of occupation on a once sloped (figure 1(b)) or undulating (figure 1(c)) surface become separated into many different vertical ‘spits’, and artefacts related to each other may never be associated.

Figure 1: Illustration of effect of palaeosol on interpolated vertical spread of finds

In recent years, more and more attention has been focused on the retrieval and analysis of information from smaller and smaller scales within archaeological sites as it becomes easier and easier to record artefacts at higher and higher resolutions (and in three dimensions) with specialist survey equipment (e.g. Dibble and Lenoir 1995, Schadla-Hall and Lane forthcoming). However, the means of relating artefacts to potential stratigraphic levels (whether clearly visible or not) is far from straightforward (Harris and Lock 1996). The need to develop a method for interpreting phasing on early prehistoric sites has become more pressing, particularly with increasing interest in the repeated use of particular sites (often described as ‘persistent places’, Barton et al 1995). Identifying repeated occupation by groups with similar technologies depends on differentiating phases of occupation on excavated sites. Developing methods for excavating and modelling sites without visible phases. In the 1994-1996 seasons of excavations on Marsden moor (Spikins 1994, 1995a, 1995b, 1996, 1999, Conneller 1999, Spikins, Scaife and Conneller in prep., Spikins (ed.) in prep), two artefact scatters were selected for excavation by recording the artefact locations in three dimensions as well as a grid of points describing sedimentological boundaries (using laser theodolite based survey equipment). The analysis and interpretation of these two ‘sites’ – one from the Early Mesolithic period, and one from the Late Mesolithic – allowed the development of a method for linking artefact distributions to recorded stratigraphy, assessing the disturbance of artefacts, and formed the basis for interpretations of the nature of occupation at the two sites.

Site 1 In the 1994 season of excavations, an area of 3m by 4m at March Hill Carr (NGR 400760, 412853), called ‘Trench A’ were excavated. Within this area, a distinctive Late Mesolithic industry (of about 1000 pieces) was recovered – typical of what has been termed the ‘scalene triangle’ microlith, 'triangle site' (Radley et al 1974) or ‘March Hill’ industry (Jacobi 1976; 1979), common in the Pennines. Apparently associated with this assemblage were two clearly formed hearths, dated to approximately 5800bp1. Careful excavation began from 15cm above the base of the peat, with excavations being carried out under a specifically designed clear plastic tent. All artefacts over 5mm (or smaller if retouched) – 909 artefacts in total - were individually numbered and recorded in three dimensions using a Geotronics geodimeter 501 (with internal memory store) and planned on recording sheets. All excavated sediment was ‘hand sieved’ to check for artefacts (in the wet peat sediment or clay it is impossible to dry sieve sediment and thus this process involved systematically ‘flaking’ sediment into the sieve and checking this). Within each metre square, each four half metre squares were excavated separately. Wet-sieving was impossible in the field because of the nature of the deposits (because of the organic nature of the peat it required drying before being wet-sieved) so a large sample bag of sediment from one quadrant of each metre square was taken back to the laboratory for wet-sieving to check artefact recovery rates. Three major sedimentological changes typical of upland Pennine acid peat soils were visible in the field – first the base of a peat cover (about 80cm in depth) which overlay a grey mineral soil (effectively the old palaeosol), under which lay an interface between this mineral soil and the sandstone (often termed the ‘natural’) which it covers. A further lower level within the sandstone consisted of a very distinctive iron pan. The iron pan is likely to have formed after Mesolithic occupation, 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 2.) appeared to relate to distinctive activity patterns around the hearths (see Spikins, Ayestaran and Conneller 1995 and for a discussion of a later extension of the site, see Spikins 1996 and Conneller 1999). 'Gaps' in the distributions even appeared to represent individual knappers. The dimensions of the artefact concentrations accorded well with experimental data (Newcomer and Sieveking 1980, Barton and Bergman 1982, Collcutt, Barton and Bergman 1990) i.e. a tendency for concentrations of debris from blade production to spread over only about 1m diameter, rarely exceeding 2m in diameter. Moreover, the distance of gaps in the distribution (and thus 'potential flint knappers' from the hearths) accorded well with Men’s model (Binford 1983) with people at a distance of approximately one and a half meters from a central hearth. 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 had had a major influence on the distribution of artefacts, forming a chance association around the two hearths. Since upland Mesolithic sites 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

1 Hearth 1, 5790±35 OxA-6296, 5813±22 UB-4050, hearth 2, 5835±35 OxA-6297, 5824±28 UB-

4051.

the context of the specific activities which might be reconstructed, but also in terms of the potential for recovering other similar upland sites.

Figure 2: Artefact refit patterns at March Hill Site 1 (Trench A)

One accepted method of assessing the integrity of these types of sites is to assess the vertical displacement of artefacts (see for example Barton 1987). The vertical displacement of the finds from the 1994 season's excavations at site 1 is shown in figure 3. A major problem exists with this method however – the vertical displacement of the artefacts is taken from a flat horizontal datum (in effect sea-level), however we know that the original positions of the artefacts were on an old palaeosol, which was neither flat nor horizontal (in fact the mineral soil surface was noted not only to be gently sloping, at approximately 5°, but also to be notably undulating).

Figure 3: Vertical displacement of finds from Site 1 with no interpolated palaeosol surface

A GIS based method provided a potential solution to these questions. Points on each of the soil interfaces had been recorded as the area was excavated, in a 0.5m spaced grid (as the area was excavated according to half metre squares, the interfaces were recorded in the sections of these squares, with readings being taken on several occasions to give an average for each point). First, the gridded points taken from each sediment interface was interpolated to produce three surfaces (see figure 4) corresponding to the soil interfaces. The method used for this interpolation is essentially the same as that for modelling much larger scale landscape surfaces, a very common use of GIS (for examples see Allen, Green and Zubrow 1990, Gaffney and Stancic 1991, Lock and Stancic 1995, Aldenderfer and Maschner 1996, and for a discussion of techniques see Christopherson, Huertin and Kunzman 1993, Haigh 1993, Kvamme 1990; 1992, Harris 1998). In this case, the points were entered into ArcInfo as a series of points used to form a TIN (triangular irregular network) surface and interpolated using quintic interpolation to calculate a surface from which the z co-ordinates of any point could be determined.

Figure 4: Surface interpolating of stratigraphic levels at Site 1

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 (figure 1(d)). This is done within GIS by ‘projecting’ the artefacts onto each surface and subtracting the ‘projected’ height from the actual excavated height. In effect, by calculating the height of each soil surface at each x,y point (for each artefact) and then the difference between this height and that at which the artefact was recovered. The finds had very similar vertical concentration in relation to each surface, displaying a bell-shaped distribution with a standard deviation consistently less than 3.4cm (ranging from 3.19 for the sandstone/mineral soil interface, 3.27cm for the iron pan and 3.35cm for the peat/mineral soil interface). The vertical distribution of finds was remarkably tightly concentrated, shown with reference to the sandstone layer in figure 5(a). We may assume that maximum vertical concentration of artefacts marks the past land surface on which they were deposited (in this case approximating to the peat/mineral soil interface).

Figure 5. March Hill Site 1: a) The vertical distribution of finds through surface interpolation of the sandstone layer b) The vertical distribution of the largest size class - cores and core fragments (solid grey line) - and the smallest – microliths and debitage (solid black line) in reference to the interpolated surface

Other lines of evidence also support the idea of a minimal vertical dispersal of artefacts from the original land surface. Microexcavation, and wet sieving using a 1mm mesh size, of a block of sediment in 1993 (Conneller 1994) revealed the same distribution patterns for micro-debitage as shown for all finds above. Likewise the results of pollen concentration analysis at this site demonstrated that pollen, spores and charcoal had not moved down the profile and become concentrated at the base of the deposits (Brayshay 1994).

In order to test the relative movement of different size classes of artefacts, the vertical distribution from the modelled stratigraphy of the largest size class - cores and core fragments - was considered separately from the smallest – microliths and debitage – see figure 5(b). The mean difference in depth between the two classes was 0.002m (95%CI from -0.006m to 0.010m); a t-test on the difference in the mean depth between the two size classes gave P=0.651. 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 peat formation, the deposition of artefacts may have coincided with a low intensity of biological processes such as earthworm activity (MacHugh 1994, Brayshay 1994). It is clear that the GIS method used provides a ‘better’ means of assessing disturbance than simply considering vertical heights (as shown in figure 3). 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. Whilst being cautious about the possibility of significant horizontal disturbance, a number of different activities and sequences of knapping activity, associated with specific refitted reduction sequences could be suggested (Conneller 1996; 1999). Moreover, the issue could be raised of the possibility of recovering other upland sites, with similar, apparently exceptional conditions of preservation. The relationship between artefact distributions and stratigraphic levels is also relevant to other questions. The questions raised by the excavations at site 2 for example were distinctively different. However, once again, a GIS method for modelling sedimentological levels and relating these to artefact distributions proved a valuable tool. Site 2 A further series of excavations were carried out at Lominot to the south (site 2) as part of the 1996 field season of the West Yorkshire Mesolithic Project. At this site (NGR 400631, 412330), the assemblage, consisting of over 500 finds excavated over 14m2 was apparently associated with a number of features, including a small but clear stakehole (see figure 6). The artefacts were made up of a combination of two subtly different raw material and artefact types. One consisted of pieces of comparably large size, made of a distinctive white or grey flint known as ‘wolds flint’ on which the diagnostic artefact types were those normally associated with the Early Mesolithic. The other, with typically smaller pieces, made on darker local ‘drift’ flint material was associated with artefact types typically diagnostic of the Late Mesolithic. However, aside from the feeling in the field that the former type seemed generally to be recovered at lower levels than the latter (an observation recorded by Francis Buckley in his nearby excavations in the 1920s, Buckley unpubl.) there was no contextual difference between the two. Without any stratigraphic evidence to suggest two (or at least two) separate phases of activity it is thus difficult to justify separating the two assemblages purely on the basis of raw material type, and also impossible to relate the features to any specific occupation or series of activities. Although the two distinct raw material types are generally associated with pieces diagnostic of the two periods, analysed assemblages come from museum collections of much antiquity which are probably quite ‘mixed’, with very few assemblages available from recent controlled excavations to confirm the purity of assemblages from each phase.

Figure 6: Plan of March Hill Site 2 (Trench C)

The sedimentological levels noted at site 2 were somewhat different from those at site 1. In this neighbouring location, soils were typically a peaty gley, rather than the typical peaty gleyed podzol encountered at site1. That is, underlying the peat and mineral soil/palaeosol layers was a gleyed grey clay, and a deeper level of gley blue clay. As for site 1, the locations of all artefacts were recorded in three-dimensions and gridded points at 0.5m intervals were recorded for each of the sedimentological levels. In principle the GIS based method described above could also be used to differentiate different phases of occupation of a site – if enough sedimentation occurred between the two phases and if the displacement of artefacts from their original levels (modelled through modern sedimentological levels) was sufficiently minimal. The same process of interpolation of the surfaces and calculation of the relationship of the finds to these surfaces was carried out as that described above for site 1. However, the distribution of the artefacts from the mineral soil interface at site 2 proved very different from that at site 1, not only were the artefacts more widely distributed vertically from this surface, but also the distribution appeared to be a bimodal one (see figure 7(a)). In order to test if the two peaks represented distinct phases of occupation, ‘Early’ and ‘Late’ activity, the displacement of artefacts identifiable to different raw material or typological types were considered separately.

The results of considering the distribution of ‘wolds’ (typically considered to be primarily used in the Early Mesolithic) and ‘drift’ (typically considered to be primarily used in the Late Mesolithic) flint and diagnostically ‘Early’ and ‘Late’ pieces are shown in figure 7(b) and (c). Whilst each phase presents a wider distribution that than recorded for Site 1, two phases of artefact deposition are nonetheless distinct.

Figure 7: a) Distribution of artefacts from mineral soil surface at March Hill Site 2 b) Distribution of drift flint (solid black line) and wold flint (solid grey line) c) Distribution of Late Mesolithic (solid black line) and Early Mesolithic (solid grey line) artefacts

A simple t-test (table 1) shows a statistically significant difference between the elevation above

sea level for Wolds and drift flint. There is a mean difference of 65cm (95%CI from 52cm to

76cm). Using the depth below soil surface we again see a statistically significant difference

(P <0001) but we see a greater difference in depths: 70cm (95%CI from 60cm to 81cm). Using

the interpolation method means we see a 05cm greater difference in the depths. If we consider the two typologically different groups (table 2) we still see a statistically significant difference between the elevation above sea level for Early and Late artefacts. There is a mean

difference of 70cm (95%CI from 49cm to 92cm). Using the depth below soil surface we once

again see a statistically significant difference (P <0001) but we see a greater difference in depths:

82cm (95%CI from 63cm to 100cm). Using the interpolation method means we see a 12cm greater difference in the depths. Table 2: The mean difference (with 95% CI) in level of artefacts made using Wolds and Drift flint by the two different measuring schemes (P value is for associate t-test).

Variable Source N Mean (m) Difference From To P (95% CI)

Elevation above sea level

Wolds 257 434.484 -0.065 -0.076 -0.052 <0.001

Drift 113 434.549

Depth beneath soil surface

Wolds 257 0.064 0.070 0.060 0.081 <0.001

Drift 113 -0.006

Table 2: The mean difference (with 95% CI) in level of early and late artefacts by the two different measuring schemes (P value is for associate t-test).

Variable Period N Mean (m) Difference From To P (95%CI)

Elevation above sea level

Early 84 434.486 -0.070 -0.092 -0.049 <0.001

Late 40 434.557

Depth beneath soil surface

Early 84 0.075 0.082 0.063 0.1 <0.001

Late 40 -0.006

Table 2: In both cases, since the stratigraphic levels sloped only slightly, and were relatively flat a distinction between the two phases is also apparent form the vertical distribution of artefacts (above sea level) alone. However the margin of certainty in distinguishing the two distributions is

better using stratigraphic interpolation. We get an increase of approximately 05cm to 10cm in the mean difference. This difference could be critical in conditions where such accurate recording is not possible or where the slope of the stratigraphic levels is greater. The clear distinction between the two levels revealed by the stratigraphic interpolation method proved useful in making interpretations about activities on the site. The two apparent phases of occupation of the site could be discussed separately (the two phases separated on the basis of raw material type are shown in figures 8(a) and (b)). This separation revealed an Early occupation largely covering the north and east of the excavated area, with the Late being very concentrated around a patch of burnt soil in the south. Specifically, it was also possible to suggest that the stakehole is most likely to belong to the Early phase, being apparently spatially associated with a cluster of Early material.

Figure 8: Phases at Site 2 separated according to raw material type a) inferred Late Mesolithic occupation b) inferred Early Mesolithic occupation

The results were also significant in a broader context since the method may provide a possibility for identifying the re-occupation of other sites where clear contextual differences between phases are not identifiable – a common situation in the case of hunter-gatherer or mobile Neolithic occupations for example, where at the same time the issue of the use of ‘persistent places’ is often important. This and the previous example clearly illustrate that GIS based stratigraphic interpolation can be a useful method for testing first the effect of vertical post-depositional processes (site 1) and secondly attempting to identify different phases of occupation (site 2). However there may potentially be a wider range of applications under conditions and at scales not considered here. It may be helpful to outline some pointers towards potential developments of the technique. Further considerations for using GIS based stratigraphic interpolation The two applications described above provide an illustration of the usefulness of the method developed here, however the technique used could also be valuable in other contexts or using slightly different methods. In the above examples, GIS based stratigraphic interpolation was used as part of the post-excavation analyses of a small excavation but clearly it could also be a useful technique either for preliminary analyses of certain sites or conversely for interpretation of much larger scale or more complex contexts. Thus the technique could conceivably be used routinely to provide a means of 'prior testing' of vertical post-depositional processes on a sample of certain sites prior to excavation. Equally, it may provide a means of identifying multiple phases in large complex sites, such as many multi-occupation cave sites or other types of major excavations such as shell middens. Alterations to the methods described may be appropriate in certain circumstances. For example, a more precise model of surfaces could be generated using a smaller grid size and higher density of points. However a compromise needs to be reached between the advantages of a smaller ‘grid’ of recorded soil interfaces in terms of accuracy of the surface models and the potential limitations or

feasibility of smaller ‘box’ sizes in excavations. Equally field conditions may also pose other limitations necessitating a more ‘coarse-grain’ approach, the lack of precision 3d recording equipment for example being one possible problem. Nonetheless, even where this type of equipment is not available similar results can be achieved through excavating in very shallow spits (as described in Spikins, Ayestaran and Conneller 1995) again recording the stratigraphy in 0.5m grid sections. In general terms of course the success of any application would depend on factors such as the clarity of soil distinctions, and in the case of identifying different phases on the extent of post-depositional movement of artefacts or the rate of sedimentation between phases. Nonetheless, there seems to be a case for using the method even where much post-depositional disturbance or minimum distinctions between phases are suspected in order that these ideas can be 'tested' (in the cases described above the level of integrity of the site was surprising, and had not the method been used other low-precision excavation methods might have been seen as appropriate). Even where the soil distinctions are not visible in the field, a good case may be made for linking three-dimensional artefact distributions to potential surfaces using GIS – it is possible for example to suggest the location of past palaeosols not visible in the field using projection pursuit clustering techniques. Conclusions Careful excavation, three-dimensional recording and the use of GIS to model sedimentological levels jointly proved very valuable tools in the analysis of the two Mesolithic sites described above. The results from the careful, albeit slow and painstaking excavation and three-dimensional recording of the two sites 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 (Heywood, Cornelius and Carver 1998), 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 left by mobile groups, 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. Acknowledgements The excavations described above were made possible by the financial support of English Heritage, under the management of West Yorkshire Archaeology Service (with particular thanks to Dave Berg at West Yorkshire Archaeology Service). We would particularly like to thank the field teams in the 1994 and 1996 seasons mentioned here, without whom the success of the project would not have been possible. Penny Spikins would like to acknowledge the support of a Sir James Knott research fellowship at the University of Newcastle, and in the final editing stage a Leverhulme study abroad grant.

Figures Figure 1. The effect of palaeosol topography on the interpreted vertical distribution of artefacts.

(a) The perceived vertical distribution of artefacts with a level palaeosol. (b) The perceived vertical distribution of artefacts with a sloping palaeosol. (c) The perceived vertical distribution of artefacts with a undulating palaeosol. (d) The calculated vertical distribution of artefacts from an interpolated surface.

Figure 2. Site 1 (March Hill Carr, Trench A) excavations in 1994 showing refit patterns Figure 3. The vertical displacement of artefacts from site 1 according to height asl (above sea level) Figure 4. Interpolated stratigraphic surfaces at site 1. Figure 5. (a) The distribution of finds at site 1 with reference to the interpolated stratigraphy (the

top of the sandstone). (b) The distribution of microliths and debitage v. cores and core fragments at site 1, with reference to the interpolated stratigraphy (the top of the sandstone)

Figure 6. Artefact distributions at the Site 2 excavations (Lominot Trench C) Figure 7. (a) Vertical distribution of artefacts at site 2 on the basis of interpolated stratigraphy.

(b) Vertical distribution of artefacts at site 2 on the basis of interpolated stratigraphy separated for 'wold' and 'drift' raw material types. (c) Vertical distribution of artefacts at site 2 on the basis of interpolated stratigraphy separated for diagnostically 'Early' and 'Late' artefacts.

Figure 8. (a) Distribution of 'wolds' flint artefacts (earliest occupation phase) (b) Distribution of 'drift' flint artefacts (latest occupation phase)

Table 1. The mean difference (with 95% CI) in level of artefacts made of Wolds and drift flint by the two different measuring schemes (P value is for associated t-test)

Table 2: The mean difference (with 95% CI) in level of early and late artefacts by the two different

measuring schemes (P value is for associated t-test) Authors P. Spikins (for correspondence) Department of Archaeology, University of Newcastle-upon-Tyne, NE1 7RU, UK. Museo de Rada Tilly, Martín García 176, Rada Tilly, 9001 Chubut, Patagonia, Argentina C.Conneller Department of Archaeology, University of Cambridge, Downing Street, Cambridge, UK H. Ayestaran Avenida Armada Argentina 438, Rada Tilly, 9001 Chubut, Patagonia, Argentina. B. Scaife Sub-Unit for Medical Statistics, Nuffield Institute for Health, 71-75 Clarendon Road, Leeds, LS2 9PL, West Yorks, UK.

References Aldenderfer, M. & Maschner, H.D.G. (eds) (1996). Anthropology, Space, and Geographic

Information Systems. New York: Oxford University Press.

Allen, K.M.S., Green, S.W. & Zubrow, E.B.W. (eds.) (1990). Interpreting Space: GIS and archaeology. London: Taylor & Francis.

Barton R.N.E. (1987). Vertical Distribution of Artefacts and Some Post-Depositional Factors Affecting Site Formation. In Rowley-Conwy P., Zvelebil M. & Blankholm H.P., (eds.). Mesolithic North-West Europe: Recent Trends. John R. Collis. pp. 55/62

Barton, R.N.E. & Bergman, C.A., (1982). Hunters at Hengistbury: some evidence from experimental archaeology. World Archaeology 14.2. pp 237/248.

Barton, R.N.E., Berridge, P.J., Walker, M.J.C. & Bevins, R.E. (1995). Persistent places in the Mesolithic Landscape: an example from the Black Mountain Uplands of South Wales. Proceedings of the Prehistoric Society 61. pp 81/116.

Brayshay, B. (1994). Pollen analysis from hearth and peat deposits, March Hill, Marsden Moor: an interim report. In Spikins 1994.

Buckley, F. (unpublished) Notebooks. Tolson Memorial Museum. Huddersfield. pages not numbered.

Christopherson, G.L., D.P. Guertin, M.R. Kunzmann et al. (1993). Comparison of Interpolation Algorithms for Digital Elevation Model Generation and Subsequent Viewshed Analysis. In Rowlands, P.G., C. Van Riper III & M.K. Sogge (eds) Proceedings of the First Biennial Conference on Research in Colorado Plateau U.S. National Parks. Transactions and Proceedings, Series 10. Denver: U.S. National Park Service, Natural Resources Publication Office. pp. 226/233.

Collcutt, S.N., Barton, R.N.E. & Bergman, C.A. (1990). Refitting in context: A taphonomic case study from a Late Upper Palaeolithic site in sands on Hengistbury Head, Dorest, Great Britain. In E. Cziesla (ed) The Big Puzzle. Bonn: Holos. pp 219/235

Conneller, C. (1994). Microexcavation: March Hill Carr. Appendix 6 of P. A. Spikins West Yorkshire Mesolithic Project 1993. Internal publication West Yorkshire Archaeology Service.

Conneller, C. (1996). Lithics Report, West Yorkshire Mesolithic Project 1995 season. In Spikins 1996

Conneller, C. (1999). March Hill Mesolithic Project, Overview of the lithic industries, West Yorkshire Archaeology Service.

Dibble, H.L. & Lenoir, M. 1995 The Middle Palaeolithic site of Combe-Capelle-Bas, France. University of Pennsylvania, Philadelphia

Gaffney, V. & Stancic, Z. (1991). GIS approaches to regional analysis: A case study of the island of Hvar. Ljubljana: Znanstveni inštitut Filozofske fakultete, University of Ljubljana, Yugoslavia, (reprinted 1996).

Haigh, J.G.B. (1993). Practical Experience in Creating Digital Terrain Models. In Andresen, J., T. Madsen & I. Scollar (eds) Computing the Past: Computer Applications and Quantitative Methods in Archaeology 1992. Aarhus: Aarhus University Press. pp. 67/73.

Harris, T.M. (1988). Digital Terrain Modelling and Three Dimensional Surface Graphics for Landscape and Site Analysis in Archaeology and Regional Planning. In (Ruggles, C.L.N. & S.P.Q. Rahtz eds.) Computer Applications and Quantitative Methods in Archaeology 1987. BAR International Series 393. Oxford: British Archaeological Reports. pp. 12/16.

Harris, T.M. & Lock, G.R. (1996) Multi-dimensional GIS: exploratory approaches to spatial and temporal relationships within archaeological stratigraphy, in H. Kamermans and K. Fennema Interfacing the Past: Computer Applications and Quantitative Methods in Archaeology CAA95 (vol II), Analecta Praehistorica Leidensia 28, University of Leiden

Healy, F., Heaton, M. & Lobb, S.J. 1992 Excavations of a Mesolithic site at Thatcham, Berkshire. Proceedings of the Prehistoric Society 58, 41-76

Heywood, I. , Cornelius, S. & Carver, S. (1998) An Introduction to Geographical Information Systems, Addison Wesley Longman

Jacobi, R. M. (1976). Aspects of the Postglacial Archaeology of England and Wales. unpublished PhD Thesis. Cambridge.

Jacobi, R. M. (1979). Early Flandrian hunters in the south-west. Proceedings of the Devon Archaeological Society 37. pp 49/88.

Kvamme, K.L.. (1990). GIS Algorithms and Their Effects on Regional Archaeological Analysis. In (Allen, K.M.S., S.W. Green & E.B.W. Zubrow eds.) Interpreting Space: GIS and Archaeology. London: Taylor & Francis. pp. 112/126.

Kvamme, K.L.. (1992). Terrain Form Analysis of Archaeological Location Through Geographic Information Systems. In (Lock, G.R. & J. Moffett eds.) Computer Applications and Quantitative Methods in Archaeology 1991. BAR International Series 577. Oxford: Tempus Reparatum. pp. 127/135.

Lock, G. & Stancic, Z. (eds.) (1995). Archaeology and Geographical Information Systems: a European Perspective. London: Taylor & Francis.

MacHugh, M. (1994). Micromorphology report, March Hill 1993 season. In Spikins 1994.

Mellars, P. 1987 Excavations on Oronsay: Prehistoric human ecology on a small island. Edinburgh University Press, Edinburgh.

Mithen, S. & Lake, M. 1996 The Southern Hebrides Mesolithic Project. In (T. Pollard & A. Morrison eds.), The Early Prehistory of Scotland, Edinburgh University Press, Edinburgh, pp.123-151.

Newcomer, M.H. & Sieveking, G. de G. (1980). Experimental flake scatter-patterns: a new interpretative technique. in Journal of Field Archaeology 7. 345-352.

Radley, J. Tallis, & Switzur, V.R. (1974). The excavation of three Narrow Blade Mesolithic sites in the Southern Pennines, England. Proceedings of the Prehistoric Society 40: 1-19.

Schadla-Hall, T. & Lane, P (forthcoming) Hunter-gatherers in the landscape: archaeological and palaeoenvironmental investigations in the Vale of Pickering N. Yorkshire 1976-1997.

Spikins, P. A. (1994). West Yorkshire Mesolithic Project Site Report: 1993 season. West Yorkshire Archaeology Service Rep. 168.

Spikins, P. A. (1995a). West Yorkshire Mesolithic Project Lithics Report. West Yorkshire Mesolithic Project Site Report 1994 Season. West Yorkshire Archaeology Service Rep. 259.

Spikins, P. A. (1995b). West Yorkshire Mesolithic Project Site Report 1994 season, West Yorkshire Archaeology Service Rep. 259.

Spikins, P. A. (1996). West Yorkshire Mesolithic Project Site Report 1995 season, West Yorkshire Archaeology Service Rep. 403

Spikins, P. A. (1999). West Yorkshire Mesolithic Project Site Report 1996 season, West Yorkshire Archaeology Service.

Spikins, P. A., Ayestaran, H. E. & Conneller, C. (1995). Meaningful patterns or mere pictures: The influence of collection strategy on the interpretation of lithic scatters. In (J. A. Schofield ed.) Lithics in Context: 125-137. Lithics Studies Society Occasional Papers no. 5. Lithics Studies Society.

Spikins, P. A.., Scaife, B., & Conneller, C.J. (in prep). West Yorkshire Mesolithic project website and CD-ROM

Spikins, P.A. (ed.) in prep. Mesolithic hunter-gatherers in the Central Pennines – excavations at Saddleworth-Marsden moor