FORMATION AND DEFORMATION PROCESSES
5.1 Introduction
The pile dwelling of Villaggio delle Macine, as already mentioned (Chapter 1), is located in central Italy, near Rome, across the northern shore of the volcanic Albano Lake. It is dated between the 19th and 16th centuries BC (Chiarucci 1985, 1986-88, 1995-6; Angle et al. 2002;
Zarattini 2003; Angle 2007; Angle et al. 2014). A more specific chronology is provided by recent radiocarbon dating as 2140-1490 BC cal. 2σ, derived from 7 pile samples, CEDAD, University of Salento (Angle et al. 2014). Although such lakeside settlements are quite widespread during this time-span in Northern Italy and, less extensively, in the Lazio region (at Lake Mezzano, for instance, as discussed in Sadori et al. 2004), the Villaggio delle Macine stands out in Tyrrhenian Italy for its width (between one to two hectares) (Angle et al. 2014:
315-6) as well as for the richness and variety of its archaeological remains, both ecofacts and artefacts. The ecofacts include unworked bones, seeds, fruits and ashes. In the artefact category fall Grotta Nuova facies ceramics, bronze artefacts (axes and daggers), a lithic industry (lithic cores, flakes and debitage), a bone industry (deer bones worked into axe handles and awls), piles, drying kilns, ambers, glassy faïence, clay fishing weights and a large number of millstones and grindstones (from which the site’s toponym derives).
The settlement was discovered in 1984, just below the surface water of the Albano crater Lake and was initially excavated as an underwater site. From 2001, a drastic contraction of the lake due to climatic factors and uncontrolled water taking led to the partial emersion of the site.
Consequently, surveys and excavation campaigns on certain key areas were carried out in 2001, 2003, 2009 and 2012 (Figure 110). As stated in Chapter 1, the material evidence retrieved during these surveys, and attributed to the last phase of site’s life and abandonment, is the cornerstone of this research. The spatial distribution of such observables, as well as the differences in frequency in more or less neighbouring locations, enable us to underline different concentrations (accumulations) of artefacts and ecofacts. They may be linked to specialised activities performed during the past in some functional areas of the site.
Figure 110 Spatial distribution of the surface surveys carried out during 2001, 2003, 2009 and 2012 at the Villaggio delle Macine.
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However, to support this assumption and thus correctly interpret the evidence, depositional and disturbance processes that actively contribute to the formation of the archaeological record have to be taken into consideration (the importance of these processes is fully explained in Chapters 2 and 3). Indeed “understanding the condition under which the material record is created helps us to develop methods for capturing important patterning in the archaeological record and interpret it in a meaningful terms” (Schmader & Graham 2015: 25). In short, this research aims to explore and clarify the role assumed by post-depositional processes in the spatial rearrangement of the material evidence. The reconstruction of such processes has to be preceded by a required overview of the depositional formation stages since, only if combined together, can these two aspects provide a much-needed increase of our knowledge and an improved understanding of the site.
Working towards this goal we faced some issues linked both to the nature of the settlement itself (pile-dwellings involve a preservation “challenge”) and to the limited funding resources.
For this reason, the site was only partially excavated and even surveys that were carried out on a wide scale have not covered the entirety of the settlement because of several natural obstacles (such as the lake itself and the presence of natural vegetation). Furthermore, the progressive site emersion involved a drastic loss of humidity that led to the decomposition of organic materials and the compression of stratigraphy, mostly near the lakeshore. There, the compacting of the archaeological record in one surface layer forced the undertaking of horizontal sampling.
Moreover, micromorphological analysis on the archaeological deposit has not yet been completed.
In spite of these limitations, a multidisciplinary approach integrating archaeological with palaeobotanical, archaeozoological and geological studies was achieved. Although these preliminary results are not exhaustive per se, together they provided a useful framework to identify as well as reconstruct possible formation and deformation processes acting on our archaeological context. Firstly, this chapter provides a general overview of these processes by showing the available data. Secondly, the current state of research on the microscale (site) as well as on the macroscale dimensions (outline of the peopling in Lazio region during the Middle Bronze Age) will be pinpointed. Furthermore, we briefly explore the methodological background related to the archaeological strategy adopted in this research, i.e. surface sampling, proving the validity of the method in the light of the aforementioned issues specific to the case study.
5.2 The pre-depositional or zero status of our wetland lacustrine archaeological context:
the formation of Lake Albano
The challenging task of past reconstruction starts from the analysis of the environmental setting which hosts the archaeological remains, the Lake Albano. It is located in the volcanic complex of the Alban Hills, South-East of Rome (Lazio, central Italy) (Figure 111), resulting from a polygenetic maar that took place during the Final Hydromagmatic phase produced this basin around 30-40 kyr BP (Fornaseri 1985; Andretta & Voltaggio 1988; De Rita et al. 1988;
Fornaseri & Cortesi 1989; Chondrogianni et al. 1996: 17; Giaccio et al. 2007; Bozzano et al.
2009: 1472). The activity of the Albano maar produced a series of eruptive units separated by paleosols.
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Figure 111 Geographic location of the study area in the framework of Alban Hills (and in a more general scale, in Italy) (from Bozzano et al. 2009: 1470, figure 1).
Albano hydromagmatic deposits are characterised by two typical lithofacies (Giordano et al.
2002). The first one, representing the majority of Albano maar deposits, is in a plane parallel to low angle cross-stratified alternation of scoria lapilli beds and ash-rich layers generally cemented (by zeolitization). The second lithofacies is represented by massive, ash-matrix supporting deposits up to 30 cm thick that contain block-sized xenoliths (again by zeolitization).
The subaerial geological frame is completed by recent talus slope and shore deposits that cover the lowest parts of the subaerial inner slopes. Lacustrine sediments cover the lake bottom (Bozzano et al. 2009: 1472).
The first bathymetric surveys of Lake Albano, realised in 1917 and 1986 (Caputo et al. 1986) did not allow for a detailed morphologic survey of submerged slopes, but rather only for the recognition of main large-sized landforms (Figure 112). In contrast, the multibeam swath bathymetric survey of Lake Albano realised in 2005 (Anzidei et al. 2007) provided contour maps and shaded relief that show the roughness and complexity of the crater (Figure 113).
Figure 112 Bathymetric maps of Lake Albano : a)from Agostini (1917); b) from Caputo et al. (1986) (from Bozzano et al. 2009: 1471, figure 3).
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Figure 113 Hillshade and morphometric maps derived from high-resolution bathymetry (Bozzano et al. 2009: 1476, figure 8).
The lake’s surface area lies at an altitude of 293 m a.s.l.; the crater rim rises generally to ca. 130 m above the lake in the west and reaches a maximum height of ca. 260 m in the south-east (Chondrogianni et al. 1996: 19). It is a hydrologically closed basin receiving water mainly from atmospheric precipitation and underwater springs. The combination of subaerial and submerged morphology permits a complete view of the Albano polygenetic maar (Figures 114A and B), whose shape is the result of the coalescence of different craters. The overall morphology is characterised by a low aspect ratio edifice distinguished by gently dipping outer slopes and steep inner slopes that correspond to the crater walls (Bozzano et al. 2009: 1473).
Figure 114 A) Three-dimensional perspective view of the volcanic depression partially filled by Lake Albano (from Bozzano et al. 2009, p. 1470, figure 2). B)Main subaqueous landslide scars (white outlines). The white numbers refer to the landslide ID of Table II; the black circles include the four areas described in the text. The viewpoints of the 3D perspective figures of the lake floor are indicated (from Bozzano et al. 2009: 1477, figure 9).
The European funded Palaeoenvironmental Analysis of Italian Crater Lake and Adriatic Sediments (PALICLAS) Project aimed at the reconstruction of the environmental evolution of central Italy within the last climatic cycle (i.e. the last 30,000 years). It consisted of physical,
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geochemical and biological studies of sediments from crater lakes and from the adjoining Adriatic Sea. Several piston cores were collected from the Albano Lake as part of this (PALB 94/1E, PALB 94/1C, PALB 94/3A, PALB 94/3B PALB 94/6A, PALB 94/6B) (Figures 115A and B). These samplings were collected at different water depths, in particular spatial locations and differ in length:
Core PALB 94/1C- PALB 94/1E (~1400 cm long, taken at a depth of 70 m) Core PALB 94/6A- PALB 94/6B (~ 840 cm long, taken at 30 m depth) Core PALB 94/3A- PALB 94/3B (~ 1100 cm collected at 120 m depth)
Cores in position 3 provide the widest chronological sequence, while those from 6 contain only late Pleistocene sediments. Finally, cores PALB 94/1C-1E cover both Holocene and Late Pleistocene lacustrine sediments (Chondrogianni et al. 1996a: 24).
Figure 115 A) locations of the analysed cores from Albano and Nemi lakes and from central Adriatic Sea (from Calanchi et al. 1996: 249, figure 1). B)Study area with the location of PALICLAS cores (dots) (from Alvisi &
Vigliotti 1996: 286, figure 1).
In particular, cores 1C and 1E showed alternation of silt layers, rich in organic matter (I) with a 2 cm thick grey tephra layer (t1) and in calcite (V-VI) with muds level (II-III-IV), interposed by a diatom layer (II). Unsorted sands and fine gravel with a coarse gravel base complete the stratigraphy (Chondrogianni et al. 1996a: 25-26) (Figure 116). The bottom of the core is composed of coarse volcanic fragments, related to a phase of Alban Hills volcanism, with fine-grained volcanic material derived from the weathering of catchment rocks occurring throughout the core (Chalanchi et al. 1996: 249-50).
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Figure 116 Lithological description of the cores P.ALB 94-1C and -1E from Lake Albano, including tephra chronology (t1, t2: calibrated ages; t3: (Ar/Ar) and radiocarbon dating (uncalibrated ages) (from Chondrogianni et al.
1996a: 25, figure 3).
In cores 3A and 3B, predominant mud layers are intercalated with diatom levels (IV), laminated intervals (V) and both of these (II, III). They end with a silt basal layer (Chondrogianni et al.
1996a: 26-29) (Figure 117). Below the lag deposit that represents the Holocene-Pleistocene boundary, the final cores (6A and 6B) showed layers predominantly composed of silt (I, II, III) intercalated with laminated muds (II), carbonates (III) and calcareous sands (IV). A detrital sand layer with a fine to medium gravel base completes the stratigraphy (a tephra layer) (Chondrogianni et al. 1996a: 30-31) (Figure 118).