Soil Micomorphology, In Encyclopedia of Geoarchaeology

830

SOIL MICROMORPHOLOGY

Schaetzl, R. J., and Anderson, S., 2005. Soils: Genesis and Geomorphology. New York: Cambridge University Press. Stafford, C. R., 1995. Geoarchaeological perspectives on paleolandscapes and regional subsurface archaeology. Journal of Archaeological Method and Theory, 2(1), 69–104. Van Andel, T. H., 1998. Paleosols, red sediments, and the Old Stone Age in Greece. Geoarchaeology, 13(4), 361–390. Vreeken, W. J., 1975. Principal kinds of chronosequences and their significance in soil history. Journal of Soil Science, 26(4), 378–394. Yaalon, D. H., 1971. Soil-forming processes in time and space. In Yaalon, D. H. (ed.), Paleopedology: Origin, Nature and Dating of Paleosols. Jerusalem: International Society of Soil Science and Israel Universities Press, pp. 29–39. Yaalon, D. H., 1975. Conceptual models in pedogenesis: can soilforming functions be solved? Geoderma, 14(3), 189–205. Yaalon, D. H., 1983. Climate, time and soil development. In Wilding, L. P., Smeck, N. E., and Hall, G. F. (eds.), Pedogenesis and Soil Taxonomy: Part 1, Concepts and Interactions. Amsterdam: Elsevier. Developments in Soil Science 11A, pp. 233–251.

Cross-references Geomorphology Landscape Archaeology Site Formation Processes Soil Stratigraphy Soil Survey Soils Stratigraphy

SOIL MICROMORPHOLOGY Panagiotis Karkanas1 and Paul Goldberg2 1 Ephoreia of Palaeoanthropology & Speleology of Southern Greece, Athens, Greece 2 Department of Archaeology, Emeritus at Boston University, Boston, MA, USA

Definitions Birefringence fabric (b-fabric): patterns of orientation and distribution of interference colors in the micromass seen in crossed-polarized light. Fabric (micro): the spatial arrangement of the soil constituents, including solid material, pores, and their shape, size and frequency. Groundmass: the coarse and fine material that forms the basic material of the soil in thin section. Microfacies: the body of sediment seen in thin section with microscopic characteristics such as composition, grain size, and sedimentary structures that are recognizably different from surrounding sediments. Pedofeature: discrete fabric units in soil material. They are characterized by different concentrations in one or more components or internal fabric from the adjacent groundmass.

Petrographic or polarized light microscope: a microscope equipped for observation of thin sections in transmitted polarized light. Sedimentary structures: bedding and surface features produced at the time of deposition. Structure (micro): size, shape, and arrangement of particles, voids, and aggregates of the soil. Soil micromorphology: the study of undisturbed soil and related materials at the microscopic level. Thin section: a thin slice (ca. 30 mm thick) of intact material glued onto a glass slide.

Introduction Soil micromorphology is the microscopic study of the soil, and since it usually employs the use of petrographic thin sections, it is similar to the geological discipline of petrography. The basic analytical equipment of soil micromorphology is the petrographic or polarized light microscope. Invented in the nineteenth century, the petrographic microscope was initially used to identify rock-forming minerals, and its application to sediments (sedimentary petrography) was undertaken by the English geologist Henry Clifton Sorby in the 1860s. Nowadays, petrographic microscopy is applied to numerous disciplines, including pedology, biology, archaeology, and environmental as well as material sciences. The application of petrographic microscopy to geoarchaeological contexts is relatively recent, but it is a corollary of the development of soil micromorphology and the interest of pedologists and geologists in archaeology. History of application In pedology, the use of the petrographic microscope began with Kubiëna (1938), who was primarily interested in using the internal organization of a soil to interpret its genesis. Soils are generally fine grained and form by sub-macroscopic processes, such as vertical transportation of fine material, solution and colloidal movements, and chemical alterations. The soil groundmass is part of a dynamic system that responds to these processes and leads to the formation of microscopic fabrics and pedofeatures that are related to soil development and origin. Therefore, the microscopic study of soils is a physical continuation of macroscopic observations of their morphology. A considerable body of literature exists on the application of soil micromorphology in pedology, including studies of fossil soils (paleosols) that have provided significant data for the study of Quaternary environments (Macphail, 1986; Macphail et al., 1987; Goldberg and Macphail, 2006). As early as the end of the nineteenth century, petrographic methods were used to understand the genesis of limestone, and later, in the early 1950s, the concept of microfacies was employed in the study of carbonate and similar sediments (Flügel, 2004). However, clastic sedimentology is first concerned with field observation of bedding and sedimentary structures. Most sedimentary

SOIL MICROMORPHOLOGY

831

Soil Micromorphology, Figure 1 Micromorphological sampling. Carved out blocks of sediment (a) are jacketed with gypsum cloth (b) to ensure safe removal. Note that the lowermost sample (no. 157221) was encased in plaster of Paris to prevent collapse of the loose sand in its lower part. Caves PP5-6, Mossel Bay, South Africa.

environments are characterized by a variety of textures, and fine-grained sediment represents a fraction of the continuum. Therefore, very few petrographic studies of finegrained sediment outside of carbonate sediments have been conducted. Such studies are mainly focused on marine muds (Förstner et al., 1968; Kuehl et al., 1988, 1991) or colluvial and mass wasting deposits (Mücher et al., 2010, and references therein). Cornwall (1958) was the first to apply micromorphology in an archaeological context, but it was not until the 1980s that micromorphology really began to be applied in archaeology (Goldberg, 1980; Courty et al., 1989). The need for a contextual approach in archaeology has found its implementation in micromorphological analysis. Archaeological deposits, in most cases, are difficult to study and interpret through field observations alone. They have a complex macrostructure, are mostly fine grained, have diverse organic and minerogenic compositions, and commonly lack obvious macroscopic sedimentary structures. Thus, microscopic study is the most logical tool to provide the basis for characterizing archaeological deposits. Similarly, depositional processes can be studied to provide the initial and basic framework for applying other techniques that can further elucidate details of formation processes. Micromorphological applications in archaeology have increased markedly during the last three decades, resulting in increased recognition of anthropogenic sedimentary processes. A new dimension in the application of micromorphology in archaeology is the introduction of microfacies as used in sedimentology (Courty, 2001). Realization has gradually emerged that, in order to provide a better integration of microscopic techniques into the archaeological record, concepts and methods of sedimentology have to be adopted. Sediments dominate archaeological settings, and therefore microfacies analysis provides a new tool for refining visual classification of features. Classification of

facies across strata is based on morphological and lithological similarities that are assumed to have similar origins and relate to the same mode of deposition (Courty, 2001). More and more studies on site formation processes are using the concept of microfacies with successful results (Macphail et al., 2004; Goldberg et al., 2009; Kourampas et al., 2009; Díaz and Eraso, 2010; Karkanas et al., 2011).

Methodology and techniques The major methodological difference between a petrographic thin section and micromorphological thin section is in the preparation of the samples: petrography normally employs rocks and indurated materials, whereas micromorphological samples are typically nonconsolidated. The first step in micromorphology is to take an undisturbed, oriented sample from excavated or natural profiles, or even cores (Figure 1). Several techniques are employed, each having its limitations (Goldberg and Macphail, 2003). One of the most typical sampling techniques is the use of Kubiena boxes, metal boxes with double lids. During sampling, one lid is removed, and the frame of the box is inserted into the soil. Then, the frame is dug out, and the lid is replaced. Kubiena boxes are suitable for relatively firm and stone-free soils or sediments. However, archaeological deposits are very heterogeneous and not always consolidated. There is substantial lateral and vertical variation, and sediments can change from very coarse to fine grained over only a few mm; they can also commonly contain coarse clasts of rock, pottery, lithics, or bones, which interfere with sampling. Complex layering and lamination as well as inclined contacts are often observed in archaeological profiles. In order to understand how these changes were formed, they must be included in a single sample that preserves all features intact. It is thus not practical to use Kubiena boxes, and a large monolith is obviously required (Figure 1).

832

SOIL MICROMORPHOLOGY

Soil Micromorphology, Figure 2 Photomicrograph of compound layered dusty clay and silt infilling and juxtaposed silt coating; left: plane-polarized light (PPL) and right: crossed-polarized light (XPL). Note the bright red birefringence due to orientation of clay laminae in XPL. Such pedofeatures have been attributed to human-induced soil disturbances (e.g., cultivation). Vashte¨mi, Albania.

There are several techniques for sampling monoliths, such as cutting blocks of appropriate dimensions using hammer and chisel out of strongly consolidated sediments or carving blocks using a sharp knife in relatively firm sediment, or applying plaster of Paris or gypsum cloth to the surface of blocks carved from loose stony sediments (Figure 1) (Goldberg and Macphail, 2003). The dimensions of the sampled blocks vary according to the type of sediment, the stratigraphy of the site, the aim of the analysis, and the size of the finished thin section. Although monoliths of 15
15
40 cm are commonly collected, 10
10
15 cm-size blocks are more typical. It also follows that the stratigraphy of the site will dictate the number and location of samples and if the sampling will be systematic or selective. The samples are oven-dried at 50  C for several days and then impregnated – under vacuum if a large enough chamber exists – with polyester resin diluted with styrene or acetone. Finally, petrographic thin sections of various large formats (7
5 cm up to 8
15 cm) are prepared. The finished thin sections are studied with stereomicroscopes and petrographic microscopes at magnifications ranging from 1 to 500
. It is best to examine the thin sections first over a large area with a stereomicroscope, which permits observation of the nature of peds (natural soil particulate aggregates) in soils and the geometry of some relatively large features often encountered in archaeological deposits. Indeed, several of the patterns of arrangement of microscopic elements are best observed with a stereomicroscope or by observation of high-resolution scans of the thin sections (Arpin et al., 2002). Polished slabs of the blocks should also be examined before the thin sections are studied for the same reason. In addition, the same thin sections or polished parts of them can be studied

using an SEM to magnifications of several thousand times; at the same time, selected spots can be analyzed chemically for their elemental content with electron microprobe techniques. One of the main limitations of micromorphology in archaeology is the representation of results (see, e.g., Weiner, 2010, 74). The size of a thin section is relatively small in relation to the distribution of relevant variations observed in the sampled unit, and therefore the scale of these variations should also influence the sampling strategy. However, field observation is a prerequisite of good micromorphology, so the best sampling strategy is to establish while in the field the main facies that constitute the stratigraphy. The number and types of facies will determine the number of samples and the type of sampling. Microscopic examination of the main facies types eventually will lead to the creation of sub-facies, and in this way a refinement of the original sampling strategy will follow. As has been summarized by Courty (2001, Figure 8.3), a long-term iterative field/laboratory strategy provides the best representation of materials for interpretation.

Micromorphological analysis Under the microscope, the coarser grains (sand size and larger) are examined for mineral and organic composition, abundance, size, shape, and distribution. The finer matrix material (silt and clay) can be observed only with respect to its internal organization, which is expressed under crossed-polarized light by interference colors and birefringence. For instance, clay particles in fine textured sediments are horizontally oriented as a result of gradual settling, and this orientation displays birefringence orientation in the form of parallel extinction when observed in thin section between crossed polarizers (Figure 2).

SOIL MICROMORPHOLOGY

833

Soil Micromorphology, Figure 3 Examples of shallow sheet wash sediments: (a) Macroscan of a thin section showing laminae of well-sorted silt and sand inside crudely sorted fine-grained sediment. The sand fraction consists of single grain and aggregated material. Theopetra Cave, Greece. (b) Interbedded clay silt laminae (C), moderately sorted single-grained sand (S), and unsorted sandy-silt clay (U). Grading is observed in the lower part. PPL, Makri, Greece.

At a higher level of order is the fabric, which describes the total organization of the constituents described above, including their spatial arrangement, shape, size, and frequency of occurrence. Features that reflect the history of the material can be grouped into three types: 1. Sedimentary features relate to the source of sediments, mode of transport, deposition of clastic grains, or chemical accumulations. Deposition produces sedimentary structures, which are the direct manifestation of the depositing medium (air or various types of fluid) and energy conditions prevalent at the time of deposition (Reineck and Singh 1980, 8). They include all the bedding and surface features produced during sediment deposition (Figures 3 and 4). 2. Pedologic and postdepositional features refer to modifications of existing materials by biological, mechanical, or chemical processes. Examples include clay coatings (in voids and around grains or aggregates), excrements, and precipitation of carbonates or oxides resulting in the formation of nodules and mottles (Figure 2). 3. Anthropogenic features result from human activities and are manifested mainly by ashes, charcoal, bone, organic matter, lithics and pottery, and construction materials (Figures 5, 6, and 7). The modern terminology of soil micromorphology is largely descriptive (Bullock et al., 1985; Stoops, 2003) and commonly uses similar descriptive approaches found

Soil Micromorphology, Figure 4 Photomicrograph of sedimentary crusts (PPL). Each crust has a coarse texture at the bottom and grades upward to finer material. Kolona, Aegina, Greece.

in sedimentology. This objective terminological approach is unlike the heavily genetic one first conceptualized by Brewer (1964), which was designed for the needs of describing soils. As such, it is quite unsuited to describing

834

SOIL MICROMORPHOLOGY

Soil Micromorphology, Figure 5 Photomicrograph of burnt remains, (a) in PPL and (b) in XPL, showing burnt bone (B), charcoal (C), and oxidized burnt soil aggregates (S) inside a dark gray (in PPL) calcitic mass consisting of ash crystals with dotted appearance (in XPL) that have begun to recrystallize (light grey areas in XPL). Lakonis Cave, Greece.

sediments or even the sedimentary aspects of soils. The textbook on soil micromorphology in archaeology by Courty et al. (1989) used a more balanced approach, however, and more recent publications also use terms derived from sedimentary petrography and even from metamorphic petrology (Phillips et al., 2011).

Micromorphology and other techniques Micromorphology is often combined with other instrumental techniques to further decipher the nature of non-recognizable microscopic features. For example, the nature and origin of amorphous phosphate features in archaeological deposits have been recognized through synchrotron X-ray scattering analysis of thin sections (Adderley et al., 2006) or microprobe analysis (Karkanas et al., 1999; Macphail and Goldberg, 2000). Furthermore, there are several examples where data derived from other disciplines have been integrated with those of micromorphology to provide a more holistic interpretation of site formation processes (e.g., phytolith analysis (Albert et al., 2008), isotopic analysis (Shahack-Gross and Finkelstein, 2008; see also Weiner, 2010). However, it is important to know how the objects under analysis are organized within the sediment. For example, spores and seeds recovered from bulk, homogenized samples cannot inform us as to whether they come from layers associated with stabling remains or with burnt remains, even though they themselves are not burnt. Thus, we need to know the context of these remains, for without it, the interpretation is not only incomplete but could be erroneous. It is thus the thin section of the intact deposits that can provide the context of these organic remains. A common strategy involves systematic geological sampling of the profiles whereby sedimentological analysis of bulk samples yields quantitative information.

Bulk samples are taken back to the laboratory where a variety of analytical methods are used, such as grain-size analysis, clay and heavy mineral determination, phosphate content, organic matter and acidity, carbonates, iron content, and magnetic susceptibility among others. Although some of these methods can provide valuable information on strictly naturally deposited layers, they are of limited value in studying cultural deposits. We cannot interpret excavated earth by treating it as bulk material, because there is no possibility of unraveling the compound effects of two successive events superimposed on the same material, and we cannot differentiate between materials that produce the same analytical measurements (Courty et al., 1989). For example, wood ash and calcareous pedogenic features consist of the same mineral, calcite. Wood ash can be recrystallized to produce indurated features resembling cemented calcareous silt sediments (Karkanas et al., 2007; Figure 5). A more recent advance in micromorphology is the use of image analysis techniques (Goldberg and Whitbread, 1993; Adderley et al., 2006). Processed images are used to identify pores, grains, and dark (organic) material and to measure area, number or frequency, and shape and size parameters of objects and voids. One way of using image analysis is to compare features like void space between different microfacies or to enhance the visibility of subtle fabrics like deformation features. Quantification measurements provide a more secure basis for interpretation, but as Goldberg and Macphail (2006) acutely notice, researchers must know exactly what they are counting.

Applications The analysis of microstratigraphy and microstructure of archaeological sequences as well as the examination of

SOIL MICROMORPHOLOGY

835

Soil Micromorphology, Figure 6 Photomicrographs of plaster floors with characteristic dense mosaic fabric. The overall homogeneity is correlated with the degree of processing of the material in antiquity. (a) Pure lime replastering (L) between impure lime floors (M). Note the dusty appearance of the lower floor due to the large amounts of finely dispersed, flaky charcoal and ash inclusions. All surfaces are covered by dark organic-rich microstratified debris. The lower one (FL) is much better developed, consisting of finely laminated decayed organic matter interbedded with coarser sediment having a dense mosaic fabric. (b) Red clay finishing coats on well-prepared lime floors. The upper one was laid on a replastering surface. (c) Surface of a poorly prepared floor enriched in lime (II) relative to its clay-rich substrate (III). The overlying material is loose, mostly ashy debris (I). Note also the general dirty appearance of the floor and the occurrence of some vughs. PPL, Makri, Greece.

relationships among construction features, sediments, and their archaeological findings has been employed successfully to interpret natural depositional processes and paleoenvironmental changes, human-induced soil formations and disturbances, land management, the use of space, and the structure of sites.

Human-induced soil formations and disturbances One of the earliest applications of soil micromorphology in archaeology was the study of soil development throughout the Holocene and how humans have affected this pedogenesis (Macphail, 1986; Macphail et al., 1987). Early Neolithic cultivation resulted in extensive disturbance of parent soil material. The direct effect of tillage is reworking of the fabric, and, consequently, mobilization and translocation of loose soil material by water and

formation of pedofeatures such as dusty clay coatings, void infills, and intercalations (Figure 2) (Macphail et al., 1987). Eventually, such processes led to the depletion of soil nutrients and the formation of acid soils (podzolization). In northern European countries, the woodland cover was succeeded by poor heath lands caused by clearance, burning, and cultivation or grazing (for a review see Goldberg and Macphail, 2006, 193–210). Land management practices in the past, like manuring and disposal of urban waste in arable lands, have been successfully recognized with soil micromorphology (Davidson and Carter, 1998; Adderley et al., 2006). Evidence of manuring may include higher amounts of organic fragments with compositions indicating that they are derived from humic layers, animal dung, or hearth ashes. This activity may lead to overthickened homogeneous

836

SOIL MICROMORPHOLOGY

to high sediment concentration, such as shallow sheet wash (overland flow) along sloping surfaces, where poor separation of bedload and suspended particles is expected (cf. Bertran and Texier, 1999). Microscopically stratified deposits with angular clasts showing inclined, preferred orientations parallel to the slope and floating in a dense, finer, poorly sorted, sandy-silt matrix are interpreted as flow of liquefied sediments (Karkanas and Goldberg, 2010). In urban sites, sedimentary crusts are among the most secure evidence for the identification of outdoor facies (Matthews, 1995). They consist of alternating fineand coarse-grained laminae with evidence of grading (Figure 4). They can also be associated with vesicles and horizontal planar voids.

Soil Micromorphology, Figure 7 A photomicrograph from Sibudu Cave, South Africa, showing the contact between laminated organic matter and charcoal at the base, and a weakly bedded phytolith layer above it; trampled bone at the top occurs in a partly disaggregated phytolith-rich layer. PPL.

dark gray upper soil horizons known as plaggen soils (Courty et al., 1989, 134). Such material may later be used in site constructions, which can be readily seen in thin sections (Simpson et al., 2006). Micromorphological data on cultivation practices have to be treated with caution, however, because other processes can also produce features suggestive of cultivation. Goldberg and Macphail (2006, 203) suggest that all human and environmental factors have to be taken into consideration when studying cultivated soils. Furthermore, such micromorphological studies are often supplemented by other methods and techniques like pollen, chemical, grain-size, and image analysis, which provide additional evidence on cultivation and manuring.

Natural processes in archaeological sites In archaeological sites, natural formation processes contribute significantly to the accumulation of sediment and to the preservation or destruction of archaeological patterns. Aeolian, colluvial, high-energy, or low-energy water flow features are easily identified by micromorphology, even when they occur as mm-thick layers inside a predominantly anthropogenic deposit. Fine-scale grading, crude sorting, and orientation of particles are revealed through the microscope (Figures 3 and 4). Each of these features can be attributed to a particular natural sedimentation process, and thus the depositional regime can be identified (Courty et al., 1989). For instance, lenses of laminated and well-sorted increments of juxtaposed mineral sand and well-rounded sand-sized soil aggregates are common inside generally massive fine-grained sediment (Figure 3; Karkanas, 2001; Goldberg et al., 2007). They are related to flow events with relatively moderate

Construction materials Various construction materials include natural soil or sediments and manufactured materials (Macphail and Goldberg, 2010, and references therein). Natural sediments and soils can be in their raw state or mixed with mineral and plant tempers to produce daub, mud brick, floors, walls, roofs, and other constructions. Anthropogenic sediments like ash, charcoal, dung, bone, and organic refuse have been used in varying proportions in construction materials (Milek and French, 2007). When the context is not clear, or when constructions have decayed or been reworked, their identification is not easy. Micromorphology can aid us to identify these materials, which are usually anomalous, exotic, or characterized by unique features (e.g., straw imprints) and can place the associated archaeological findings in the right context. Furthermore, deciphering the techniques used for producing these materials may lead to inferences on craft specialization and cultural interchange (Goren and Goldberg, 1991; Karkanas, 2007). Most construction materials are characterized by microscopic features that reflect intentional human preparation. Dense mixing of constituents in the wet state produces a characteristic mosaic fabric where coarser components are embedded in a dense fine groundmass. The overall microscopic appearance, however, can be quite homogeneous because of even distribution of all clast sizes (Figure 6). Furthermore, puddling and working of material in a semi-plastic state can produce domains with oriented fabrics, silty or clayey intercalations, vughs, and vesicles (Macphail and Goldberg, 2010). Adding of plant temper is also characteristic of some construction materials like mud bricks and daub (Courty et al., 1989, 119–120). Tubular-shaped voids that are pseudomorphs of the plant temper are readily observed in thin sections. Lime plasters and mortars are characterized by a dense recrystallized fine calcitic matrix with partially burnt carbonized lime lumps that are well welded in the groundmass (Figure 6; Karkanas, 2007). It has to be stressed that in all cases, differentiation between types of construction materials is site specific. For instance, mud bricks, daub, and clay floors

SOIL MICROMORPHOLOGY

can be very similar. In each site, the best-preserved constructions have to be studied as a reference, and the sampling strategy should focus upon establishing the sequential decay of all types of construction material (Goldberg, 1979; Friesem et al., 2011). At the same time, the geometry and spatial distribution of the decayed construction features in the field have to be taken into consideration in addition to the micromorphological results in order to identify the original construction type.

Use of space Different human activities can be clearly demonstrated from the content and fabric of the sediments themselves. In prehistoric, non-constructed sites, cultural deposits are commonly burnt (Figure 5). In the Paleolithic site of Kebara Cave, Israel, distinct types of fire-related features have been identified together with remains of in situ burning as well as sediments that were dumped or moved aside in the process of cleaning and modifying living areas (Goldberg et al., 2007; Meignen et al., 2007). Burning features in undisturbed, primary context are characterized by a bright red (rubified), clay-rich substrate overlain by a black, thin, charcoal-rich layer and an often thicker, bedded, whitish ashy layer with burnt bone and red soil (rubified) inclusions. Microscopically, pristine ash consists of calcite pseudomorphs after plant structures (Wattez and Courty, 1987; Canti, 2003). The composition of raked-out hearths is similar, but the arrangement of the constituents is totally different. Bone, charcoal, calcareous ashes, and reddened soil can occur in the same stratigraphic unit or can be mixed between stratigraphic units. In addition, porosity is elevated. Trampled hearths resemble raked-out hearths, but they are more compacted and thus display reduced porosity (Meignen et al., 2007). In the Middle Stone Age of Sibudu Cave, South Africa, individual anthropogenic activities were identified, including the construction of hearths and bedding, as well as the maintenance of occupational surfaces through the sweep out of hearths and the repeated burning of bedding. Overlapping series of laminated microfacies were identified, consisting of microlaminated charred or humified organic fibers that often contained stringers of crushed charcoal or phytoliths oriented parallel to the bedding and associated with partially dissolved plant ash (Figure 7). These features were interpreted as intentionally burnt plant material used for surface preparation (bedding) (Goldberg et al., 2009). In sites characterized by human constructions, such as tells, detailed micromorphological studies of living floors, their maintenance, and the associated occupational debris have provided clues to the use of space at the site (Matthews, 1995; Matthews et al., 1994; Shahack-Gross et al., 2005; Karkanas and Efstratiou, 2009) as well as insights into pyrotechnological activities (Berna et al., 2007). Spatial and contextual variation in the type, thickness, and frequency of plaster floors and occupational deposits within and between buildings has been attributed to different uses of space (Matthews et al., 1996).

837

In Neolithic Makri, Greece, it was noted that a series of well-prepared lime-plastered floors reoccurred at relatively regular intervals over large areas of the settlement (Karkanas and Efstratiou, 2009). It was also noted that these floors were kept exceptionally clean, that they often preserve a finishing coat of red clay or laminated debris of dusty, dark organic-rich material (Figure 6), and that, rarely, a lamina of articulated phytoliths is recovered that may represent decayed organic matting (cf. Gé et al., 1993; Matthews, 1995). Between these well-prepared lime floors, layers of overlapping and randomly recurring, poorly prepared floors were identified. The top of some of these layers occasionally preserved smooth slaked surfaces, enriched in lime, that resulted from final finishing of the top of a floor or lime replastering (Figure 6c). In addition, it was possible to define microlaminated organic-rich debris on top of some of the compacted layers, particularly when these were protected by the construction of a well-prepared floor above (Figure 6a). The identification of such planar structures was a decisive criterion for defining them as in situ floors (see Macphail et al., 2006). In the investigation of ancient pastoral activities, micromorphology enables us to differentiate between animal species and possibly food sources and grazing processes on the basis of differences in the nature of the components as well as the structure and arrangement of dung remains (Figure 8) (Courty et al., 1991; Boschian and Montagnari-Kokelj, 2000; Macphail et al., 1997; Karkanas, 2006). Further progress in the understanding of stabling deposits was made by characterizing soil microfabrics formed in contemporary abandoned pastoral sites (Shahack-Gross et al., 2003, 2004). The Neolithic cave of Arene Candide in Liguria, Italy, comprises a sequence of gray, homogeneous, and stratified sediments (Macphail et al., 1997). Detailed micromorphological analysis indicates that the cave was used both for herbivore stabling and for domestic occupation. The dung layers consist of a basal, phosphate-rich, stained sub-layer of mainly uncharred plant material. This sub-layer is overlain by ashed and semi-ashed material with burnt, coarse convolute fragments of sheep and goat coprolites and finally by wood ashes. This sequence suggests that the stabling remains were frequently burnt most likely for cleaning purposes. The homogeneous sequence represents mainly domestic occupational deposits that consist of multiple layered, articulated phytoliths and plant tissues used for domestic bedding and thin red soil layers with indications of processing in a wet state. The spatial and temporal organization of domestic occupation and herbivore stabling enabled an interpretation of the changes in cave use during the Neolithic.

Postdepositional alterations Sediments are affected by a large variety of physical and chemical transformations after they have been deposited. From both sedimentological and archaeological

838

SOIL MICROMORPHOLOGY

Soil Micromorphology, Figure 8 Photomicrographs (a) PPL and (b) XPL of a slightly charred ovicaprine dung fragment inside loosely aggregated sediment consisting mainly of calcitic ashes. Bright spots in the dung shown in XPL are dung spherulites (silt-sized, 5–15 mm calcareous spheres with a pseudo-uniaxial interference under crossed-polarized light; see Shahack-Gross et al., 2004). Kouveleiki Cave, Greece.

perspectives, pedogenesis can also be included in postdepositional alterations (Courty et al., 1989). Physical, chemical, or biological processes produce certain features that are recognizable in thin sections. Each kind of microfauna produces excrements of specific shape and sometimes size (Bullock et al., 1985). Movement of materials through the sediment or soil produces microscopic textural features like void coatings and infillings (Stoops, 2003). Crosscutting relationships between these micromorphological features provide evidence for the sequence of mineral development in soils. Moreover, minerals in the process of alteration document the progress of chemical reactions (Karkanas, 2010). Analysis of all these processes contributes significantly to understanding paleoenvironmental conditions and provides insights into the completeness of the archaeological record. Commonly, archaeological deposits of Pleistocene age are affected by cryogenic processes. Evidence of freezing in sediments is revealed by a characteristic platy and lenticular microstructure (van Vliet Lanoë, 2010). In Theopetra Cave, Greece, freeze-thaw and chemical alteration have acted on the same deposits, producing a complex sequence of postdepositional events (Karkanas, 2001). In some layers, authigenic phosphate minerals fill cryogenic cracks that postdate the freezing event. In other layers, however, phosphatic features are themselves affected by freeze-thaw activity (Figure 9). Therefore, the spatial distribution of microscopic frost features and chemical alteration features permits differentiation of the superimposed cryogenic events and thereby enables a better understanding of the paleoclimatic changes in the area. Moreover, the presence of certain phosphate minerals is associated with the dissolution of bone and alteration of calcareous materials such as wood

ash (Karkanas et al., 2000). Instrumental mineralogical and microchemical techniques have been used to identify the mineral phases seen in the thin sections. In old sites, stratigraphic gaps are not readily identified by field observations due to postdepositional alterations. Identifying and separating the sequence of events that have affected the same sediment is of major importance in reconstructing the depositional history of a site. An example comes from Geißenklösterle Cave, Germany, where micromorphological analysis was able to confirm a major change in the diagenetic regime between the Middle and Upper Paleolithic sequences (Goldberg and Berna, 2010). Middle Paleolithic phosphatized sediments are sharply overlain by unweathered, calcareous Upper Paleolithic sediments. This finding helped to elucidate the nature of the so-called Middle–Upper Paleolithic transition at this particular site and placed finite constraints on what can be said about it.

Summary Applications of micromorphology in archaeology have witnessed a steady increase over the last 30 years. The microscopic study of soils and paleosols within and surrounding archaeological sites continues to provide important information for paleoenvironmental reconstructions and insights into the role of humans in shaping the environment. Human-induced soil formation and disturbances are especially relevant in this respect, and micromorphology provides basic information about how soils are constructed and how they develop. The application of micromorphology to the study of site formation processes has proved to be a very powerful tool in placing archaeological findings in their proper context.

SOIL MICROMORPHOLOGY

839

Soil Micromorphology, Figure 9 Examples of postdepositional alterations: (a) phosphates (Ph) filling planar cracks produced by freeze-thaw action; (b) frost cracks (with arrows) crosscutting phosphate deposits (Ph). PPL, Theopetra Cave, Greece.

Archaeological sites comprise a complex array of natural and anthropogenic processes, and therefore, petrographic and micromorphological methods, including ideas and concepts from different earth science disciplines, should be combined in order to yield the best results. Applying micromorphology to the study of archaeological deposits provides valuable results because the structure and fabric of sediment constituents reflect the forces and agents that deposited them. Organization of the coarser components can be readily seen with the naked eye, but the finer fractions can be seen only under the microscope. The study of archaeological sediments will greatly benefit from observations at all scales.

Bibliography Adderley, W. P., Simpson, I. A., and Davidson, D. A., 2006. Historic landscape management: a validation of quantitative soil thinsection analyses. Journal of Archaeological Science, 33(3), 320–334. Albert, R. M., Shahack-Gross, R., Cabanes, D., Gilboa, A., Lev-Yadun, S., Portillo, M., Sharon, I., Boaretto, E., and Weiner, S., 2008. Phytolith-rich layers from the Late Bronze and Iron Ages at Tel Dor (Israel): mode of formation and archaeological significance. Journal of Archaeological Science, 35(1), 57–75. Arpin, T. L., Mallol, C., and Goldberg, P., 2002. A new method of analyzing and documenting micromorphological thin sections using flatbed scanners: applications in geoarchaeological studies. Geoarchaeology, 17(3), 305–313. Berna, F., Behar, A., Shahack-Gross, R., Berg, J., Boaretto, E., Gilboa, A., Sharon, I., Shalev, S., Shilstein, S., Yahalom-Mack, N., Zorn, J. R., and Weiner, S., 2007. Sediments exposed to high temperatures: reconstructing pyrotechnological processes in

Late Bronze and Iron Age strata at Tel Dor (Israel). Journal of Archaeological Science, 34(3), 358–373. Bertran, P., and Texier, J.-P., 1999. Facies and microfacies of slope deposits. Catena, 35(2–4), 99–121. Boschian, G., and Montagnari-Kokelj, E., 2000. Prehistoric shepherds and caves in the Trieste karst (northeastern Italy). Geoarchaeology, 15(4), 331–371. Brewer, R., 1964. Fabric and Mineral Analysis of Soils. New York: Wiley. Bullock, P., Fedoroff, N., Jongerius, A., Stoops, G., and Tursina, T., 1985. Handbook for Soil Thin Section Description. Wolverhampton: Waine Research Publishers. Canti, M. G., 2003. Aspects of the chemical and microscopic characteristics of plant ashes found in archaeological soils. Catena, 54(3), 339–361. Cornwall, I. W., 1958. Soils for the Archaeologist. London: Phoenix. Courty, M.-A., 2001. Microfacies analysis assisting archaeological stratigraphy. In Goldberg, P., Holliday, V. T., and Ferring, C. R. (eds.), Earth Sciences and Archaeology. New York: Kluwer, pp. 205–239. Courty, M.-A., Goldberg, P., and Macphail, R. I., 1989. Soils and Micromorphology in Archaeology. Cambridge: Cambridge University Press. Courty, M.-A., Macphail, R. I., and Wattez, J., 1991. Soil micromorphological indicators of pastoralism with special reference to Arene Candide, Fianle Ligure, Italy. Rivista di Studi Liguri, 57 (1–4), 127–150. Davidson, D. A., and Carter, S. P., 1998. Micromorphological evidence of past agricultural practices in cultivated soils: the impact of a traditional agricultural system on soils in Papa Stour, Shetland. Journal of Archaeological Science, 25(9), 827–838. Díaz, A. P., and Eraso, J. F., 2010. Same anthropogenic activity, different taphonomic processes: a comparison of deposits

840

SOIL MICROMORPHOLOGY

from Los Husos I & II (upper Ebro basin, Spain). Quaternary International, 214(1–2), 82–97. Flügel, E., 2004. Microfacies of Carbonate Rocks: Analysis, Interpretation and Application. Berlin: Springer. Förstner, U., Müller, G., and Reineck, H.-E., 1968. Sedimente und Sedimentfüge des Rheindeltas im Bodensee. Neues Jahrbuch für Mineralogie (Abhandlungen), 109, 33–62. Friesem, D., Boaretto, E., Eliyahu-Behar, A., and Shahack-Gross, R., 2011. Degradation of mud brick houses in an arid environment: a geoarchaeological model. Journal of Archaeological Science, 38(5), 1135–1147. Gé, T., Courty, M.-A., Matthews, W., and Wattez, J., 1993. Sedimentary formation processes of occupation surfaces. In Goldberg, P., Nash, D. T., and Petraglia, M. D. (eds.), Formation Processes in Archaeological Context. Madison, WI: Prehistory Press. Monographs in World Archaeology, Vol. 17, pp. 149–163. Goldberg, P., 1979. Geology of the Late Bronze Age mudbrick from Tel Lachish, Tel Aviv. Journal of the Tel Aviv Institute of Archaeology, 6(1), 60–71. Goldberg, P., 1980. Micromorphology in archaeology and prehistory. Pale´orient, 6(1), 159–164. Goldberg, P., and Whitbread, I., 1993. Micromorphological study of a Bedouin tent floor. In Goldberg, P., Nash, D. T., and Petraglia, M. D. (eds.), Formation Processes in Archaeological Context. Madison, WI: Prehistory Press. Monographs in World Archaeology, Vol. 17, pp. 165–188. Goldberg, P., and Macphail, R. I., 2003. Strategies and techniques in collecting micromorphology samples. Geoarchaeology, 18(5), 571–578. Goldberg, P., and Macphail, R. I., 2006. Practical and Theoretical Geoarchaeology. Oxford: Blackwell. Goldberg, P., and Berna, F., 2010. Micromorphology and context. Quaternary International, 214(1–2), 56–62. Goldberg, P., Laville, H., and Meignen, L., 2007. Stratigraphy and geoarchaeological history of Kebara Cave, Mount Carmel. In Bar-Yosef, O., and Meignen, L. (eds.), Kebara Cave, Part 1. Cambridge: Peabody Museum of Archaeology and Ethnology Harvard University, pp. 49–89. Goldberg, P., Miller, C. E., Schiegl, S., Ligouis, B., Berna, F., Conard, N. J., and Wadley, L., 2009. Bedding, hearths, and site maintenance in the Middle Stone Age of Sibudu Cave, KwaZulu-Natal, South Africa. Archaeological and Anthropological Sciences, 1(2), 95–122. Goren, Y., and Goldberg, P., 1991. Petrographic thin sections and the development of Neolithic plaster production in northern Israel. Journal of Field Archaeology, 18(1), 131–138. Karkanas, P., 2001. Site formation processes in Theopetra Cave: a record of climatic change during the Late Pleistocene and early Holocene in Thessaly, Greece. Geoarchaeology, 16(4), 373–399. Karkanas, P., 2006. Late Neolithic household activities in marginal areas: the micromorphological evidence from the Kouveleiki caves, Peloponnese, Greece. Journal of Archaeological Science, 33(11), 1628–1641. Karkanas, P., 2007. Identification of lime plaster in prehistory using petrographic methods: a review and reconsideration of the data on the basis of experimental and case studies. Geoarchaeology, 22(7), 775–796. Karkanas, P., 2010. Preservation of anthropogenic materials under different geochemical processes: a mineralogical approach. Quaternary International, 214(1–2), 63–69. Karkanas, P., and Efstratiou, N., 2009. Floor sequences in Neolithic Makri, Greece: micromorphology reveals cycles of renovation. Antiquity, 83(322), 955–967. Karkanas, P., and Goldberg, P., 2010. Site formation processes at Pinnacle Point Cave 13B (Mossel Bay, Western Cape Province,

South Africa): resolving stratigraphic and depositional complexities with micromorphology. Journal of Human Evolution, 59 (3–4), 256–273. Karkanas, P., Kyparissi-Apostolika, N., Bar-Yosef, O., and Weiner, S., 1999. Mineral assemblages in Theopetra, Greece: a framework for understanding diagenesis in a prehistoric cave. Journal of Archaeological Science, 26(9), 1171–1180. Karkanas, P., Bar-Yosef, O., Goldberg, P., and Weiner, S., 2000. Diagenesis in prehistoric caves: the use of minerals that form in situ to assess the completeness of the archaeological record. Journal of Archaeological Science, 27(10), 915–929. Karkanas, P., Shahack-Gross, R., Ayalon, A., Bar-Matthews, M., Barkai, R., Frumkin, A., Gopher, A., and Stiner, M. C., 2007. Evidence for habitual use of fire at the end of the Lower Paleolithic: site-formation processes at Qesem Cave, Israel. Journal of Human Evolution, 53(2), 197–212. Karkanas, P., Pavlopoulos, K., Kouli, K., Ntinou, M., Tsartsidou, G., Facorellis, Y., and Tsourou, T., 2011. Palaeoenvironments and site formation processes at the Neolithic lakeside settlement of Dispilio, Kastoria, northern Greece. Geoarchaeology, 26(1), 83–117. Kourampas, N., Simpson, I. A., Perera, N., Deraniyagala, S. U., and Wijeyapala, W. H., 2009. Rockshelter sedimentation in a dynamic tropical landscape: Late Pleistocene-early Holocene archaeological deposits in Kitulgala Beli-Lena, southwestern Sri Lanka. Geoarchaeology, 24(6), 677–714. Kubiëna, W. L., 1938. Micropedology. Ames, IA: Collegiate Press. Kuehl, S. A., Nittrouer, C. A., and DeMaster, D. J., 1988. Microfabric study of fine-grained sediments; observations from the Amazon subaqueous delta. Journal of Sedimentary Research, 58(1), 12–23. Kuehl, S. A., Hariu, T. M., Sanford, M. W., Nittrouer, C. A., and DeMaster, D. J., 1991. Millimeter-scale sedimentary structure of fine-grained sediments: examples from continental margin environments. In Bennett, R. H., Bryant, W. R., and Hulbert, M. H. (eds.), Microstructure of Fine-Grained Sediments. From Mud to Shale. New York: Springer-Verlag, pp. 33–45. Macphail, R. I., 1986. Paleosols in archaeology: their role in understanding Flandrian pedogenesis. In Wright, V. P. (ed.), Paleosols: Their Recognition and Interpretation. Oxford: Blackwell Scientific Publications, pp. 263–290. Macphail, R. I., and Goldberg, P., 2000. Geoarchaeological investigation of sediments from Gorham’s and Vanguard Caves, Gibraltar: microstratigraphical (soil micromorphological and chemical) signatures. In Stringer, C. B., Barton, R. N. E., and Finlayson, J. C. (eds.), Neanderthals on the Edge. Oxford: Oxbow Books, pp. 183–200. Macphail, R. I., and Goldberg, P., 2010. Archaeological materials. In Stoops, G., Marcelino, V., and Mees, F. (eds.), Interpretation of Micromorphological Features of Soils and Regoliths. Amsterdam: Elsevier, pp. 589–622. Macphail, R. I., Romans, J. C. C., and Robertson, L., 1987. The application of micromorphology to the understanding of Holocene soil development in the British Isles, with special reference to early cultivation. In Fedoroff, N., Bresson, L.-M., and Courty, M.-A. (eds.), Micromorphologie des sols; Actes de la VIIe Re´ union internationale de micromorphologie des sols, Paris, juillet 1985. Paris: Association Française pour l’Étude du Sol, pp. 647–656. Macphail, R. I., Courty, M.-A., Hather, J., and Wattez, J., 1997. The soil micromorphological evidence of domestic occupation and stabling activities. In Maggi, R. (ed.), Arene Candide: A Functional and Environmental Assessment of the Holocene Sequence (Excavations Bernabò Brea-Cardini 1940–50). Roma: Memorie dell’Istituto Italiano di Paleontologia Umana, Nuova serie 5, pp. 53–88.

SOIL STRATIGRAPHY

Macphail, R. I., Cruise, G. M., Allen, M. J., Linderholm, J., and Reynolds, P., 2004. Archaeological soil and pollen analysis of experimental floor deposits; with special reference to Butser Ancient Farm, Hampshire, UK. Journal of Archaeological Science, 31(2), 175–191. Macphail, R. I., Linderholm, J., and Karlsson, N., 2006. Scanian pithouses; interpreting fills of grubenhäuser: examples from England and Sweden. In Engelmark, R., and Linderholm, J. (eds.), Proceedings from the VIII Nordic Conference on the Application of Scientific Methods in Archaeology, Umea° 2001. University of Umeå, Archaeology and Environment 21, pp. 119–127. Matthews, W., 1995. Micromorphological characterization and interpretation of occupation deposits and microstratigraphic sequences at Abu Salabikh, Southern Iraq. In Barham, A. J., and Macphail, R. I. (eds.), Archaeological Sediments and Soils: Analysis, Interpretation and Management. London: Institute of Archaeology, University College, pp. 41–74. Matthews, W., Postgate, J. N., Payne, S., Charles, M. P., and Dobney, K., 1994. The imprint of living in an early Mesopotamian city: questions and answers. In Luff, R. -M., and RowleyConway, P. (eds), Whither Environmental Archaeology? Oxford: Oxbow Monograph 38, pp. 171–212. Matthews, W., French, C. A. I., Lawrence, T., and Cutler, D., 1996. Multiple surfaces: the micromorphology. In Hodder, I. (ed.), On the Surface: Catalhöyük 1993–95. Cambridge: The MacDonald Institute for Research and British Institute of Archaeology of Ankara, pp. 301–342. Meignen, L., Goldberg, P., and Bar-Yosef, O., 2007. The hearths at Kebara Cave and their role in site formation processes. In Bar-Yosef, O., and Meignen, L. (eds.), Kebara Cave, Mt. Carmel, Israel: The Middle and Upper Paleolithic Archaeology. Part I. Cambridge, MA: Peabody Museum, Harvard University. American School of Prehistoric Research, Bulletin, Vol. 49, pp. 91–122. Milek, K. B., and French, C. A. I., 2007. Soils and sediments in the settlement and harbour at Kaupang. In Skre, D. (ed.), Kaupang in Skiringssal. Aarhus: Aarhus University Press, pp. 321–360. Mücher, H., van Steijn, H., and Kwaad, F., 2010. Colluvial and mass wasting deposits. In Stoops, G., Marcelino, V., and Mees, F. (eds.), Interpretation of Micromorphological Features of Soils and Regoliths. Amsterdam: Elsevier, pp. 37–48. Phillips, E., van der Meer, J. J. M., and Ferguson, A., 2011. A new ‘microstructural mapping’ methodology for the identification, analysis and interpretation of polyphase deformation within subglacial sediments. Quaternary Science Reviews, 30(19–20), 2570–2596. Reineck, H.-E., and Singh, I. B., 1980. Depositional Sedimentary Environments, with Reference to Terrigenous Clastics. Berlin: Springer-Verlag. Shahack-Gross, R., and Finkelstein, I., 2008. Subsistence practices in an arid environment: a geoarchaeological investigation in an Iron Age site, the Negev Highlands, Israel. Journal of Archaeological Science, 35(4), 965–982. Shahack-Gross, R., Marshall, F., and Weiner, S., 2003. Geo-ethnoarchaeology of pastoral sites: the identification of livestock enclosures in abandoned Maasai settlements. Journal of Archaeological Science, 30(4), 439–459. Shahack-Gross, R., Marshall, F., Ryan, K., and Weiner, S., 2004. Reconstruction of spatial organization in abandoned Maasai settlements: implications for site structure in the pastoral Neolithic of East Africa. Journal of Archaeological Science, 31(10), 1395–1411. Shahack-Gross, R., Albert, R.-M., Gilboa, A., Nagar-Hilman, O., Sharon, I., and Weiner, S., 2005. Geoarchaeology in an urban context: the uses of space in a Phoenician monumental building

841

at Tel Dor (Israel). Journal of Archaeological Science, 32(9), 1417–1431. Simpson, I. A., Guttmann, E. B., Cluett, J., and Shepherd, A., 2006. Characterizing anthropic sediments in north European Neolithic settlements: an assessment from Skara Brae, Orkney. Geoarchaeology, 21(3), 221–235. Stoops, G., 2003. Guidelines for Analysis and Description of Soil and Regolith Thin Sections. Madison, WI: Soil Science Society of America. Van Vliet-Lanoë, B., 2010. Frost action. In Stoops, G., Marcelino, V., and Mees, F. (eds.), Interpretation of Micromorphological Features of Soils and Regoliths. Amsterdam: Elsevier, pp. 81–108. Wattez, J., and Courty, M.-A., 1987. Morphology of ash of some plant materials. In Fedoroff, N., Bresson, L.-M., and Courty, M.-A. (eds.), Micromorphologie des sols; Actes de la VIIe Re´ union internationale de micromorphologie des sols, Paris, juillet 1985. Paris: Association Française pour l’Étude du Sol, pp. 677–683. Weiner, S., 2010. Microarchaeology: Beyond the Visible Archaeological Record. Cambridge: Cambridge University Press.

Cross-references Anthrosols Chemical Alteration Electron Spin Resonance (ESR) in Archaeological Context Hearths and Combustion Features Kebara Cave Microstratigraphy Pastoral Sites Petrography Scanning Electron Microscopy (SEM) Site Formation Processes Soils Tells

SOIL STRATIGRAPHY Vance T. Holliday1, Rolfe D. Mandel2 and Timothy Beach3 1 Anthropology and Departments Geosciences, University of Arizona, Tucson, AZ, USA 2 Department of Anthropology, University of Kansas, Lawrence, KS, USA 3 Department of Geography and the Environment, The University of Texas at Austin, Austin, TX, USA

Introduction Soil stratigraphy or pedostratigraphy is a way of grouping and correlating sediments and rocks based on soil-related, or pedogenic, criteria. This contrasts with lithostratigraphy (classification based on lithological characteristics such as color or grain size), chronostratigraphy (classification based on age of deposits or rocks), and biostratigraphy (classification based on biological characteristics such as pollen or vertebrate fauna) (see the entry on “Stratigraphy” in this volume). It has been defined as “the study of different soil associations formed in an area during past periods of varied soil-forming conditions” Catt