Degradation of mud brick houses in an arid environment: a geoarchaeological model

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Journal of Archaeological Science 38 (2011) 1135e1147

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Journal of Archaeological Science

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Degradation of mud brick houses in an arid environment: a geoarchaeologicalmodel

David Friesem a,b, Elisabetta Boaretto a,b, Adi Eliyahu-Behar b, Ruth Shahack-Gross a,b,*

aDept. of Land of Israel Studies and Archaeology, Bar-Ilan University, Ramat-Gan 52900, IsraelbKimmel Center for Archaeological Science, Weizmann Institute of Science, Rehovot 76100, Israel

a r t i c l e i n f o

Article history:Received 4 November 2010Received in revised form19 December 2010Accepted 24 December 2010

Keywords:Mud bricksSite formation processesDegradation processesFourier-transform infrared (FTIR)spectroscopyX-ray Fluorescence (XRF)Micromorphology

* Corresponding author. Dept. of Land of Israel StudUniversity, Ramat-Gan 52900, Israel.

E-mail address: ruth.shahack@weizmann.ac.il (R. S

0305-4403/$ e see front matter � 2011 Elsevier Ltd.doi:10.1016/j.jas.2010.12.011

a b s t r a c t

A common assumption in Near Eastern tell archaeology is that the majority of sediments originate fromdegraded mud bricks. Little is known about the mechanism of mud brick wall degradation. Here wepresent a detailed macro- and microscopic ethnoarchaeological study of the degradation of a mud brickhouse and propose a comprehensive mechanism for tell formation processes in arid environments. Thestudy took place in southern Israel by trenching a ca. 60 year old abandoned mud brick house, followedby extensive sediment sampling. Macroscopic observations showed that mud brick walls degrade bycollapse of single bricks and/or collapse of intact wall parts, either inwards or outwards. In addition, infillsediments within the house and outside it, in close proximity to its walls, form alternating sedimentarylayers of various colors and textures. The degraded mud brick material lost its distinctive macroscopicstructure, which makes it impossible to accurately identify this material by field observations alone.Mineralogical and elemental analyses established the sources of the house infill sediments, namely mudbricks and wind blown sediments. Alternating layers mostly originate from mixing between degradedmud brick material and wind blown sediments. Micromorphological observations revealed microscopicmechanisms of mud brick degradation and include processes of mud slurry gravity flows, sedimentcoatings and infillings, wind abrasion of walls, small-scale puddling, and bioturbation. This studyprovides a working scheme for site formation of abandoned mud brick structures in arid environments. Itprovides a set of criteria by which it is possible to differentiate floors from post-abandonment sedi-mentary features and thus improves the reliability of activity area research.

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1. Introduction

The study of human made mud bricks offers a wealth of archae-ological information. It contributes to our understanding of sitearchitecture, social issues related to buildings/houses, human selec-tion and procurement of soil raw material, site formation, sitestratigraphy, the influence of these activities on the landscape, andpost-abandonment processes (Goldberg, 1979; Goodman-Elgar,2008; Matthews et al., 1997; Rosen, 1986; Shahack-Gross et al.,2005; Stevanovic, 1997). Extracting archaeologically this wealth ofinformation is hampered by the fact that unfired mud bricks areprone todegradation.Athistorical tell sites in the southern Levant, forexample, mud brick walls are rarely preserved and architecturalreconstructions are often based on presence of stone foundationsonly. InNear Eastern tells it is often assumed thatmost sediments are

ies and Archaeology, Bar-Ilan

hahack-Gross).

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a result ofmud brick degradation (e.g., Davidson,1973; Goldberg andMacphail, 2006; Rosen, 1986) and the term “mud brick material” isoften used by field archaeologists to point out sediments that areassumed to be the degradation product of mud bricks. Field identi-fication of this so-called “mud brick material” is based on intuitionand lacks standardization and definition. Criteria for the identifica-tion of decayedmudbricks therefore vary amongexcavated sites, andeven among excavation areas at the same site. The study presentedbelow therefore aims at providing criteria for the identification ofmud brick degradation products, using macroscopic (field) andmicroscopic (laboratory based) characteristics. This was achieved byexamining the degradation of the walls of an abandoned mud brickhouse in an arid environment, and studying the accumulation of infillsediments within and around the house.

1.1. Previous research

The most common construction with earthen materials in theNear East is by using a box-shaped unit made of soil which is calleda mud brick. While studies on the taphonomy of mud bricks are

D. Friesem et al. / Journal of Archaeological Science 38 (2011) 1135e11471136

scant (see below), relatively many studies were conducted on thepreparation of bricks, building techniques, and sourcing of mudbricks at archaeological sites.

Construction with mud bricks in the Near East dates back to theearly Pre-Pottery Neolithic period, where in sites such as NetivHagdud, Jericho and Gilgal (all located in the Jordan Valley) wallswere built of plano-convex mud bricks (Bar-Yosef, 1995). Ethno-graphic and archaeological studies show that raw material for mudbrick preparation is mostly acquired from local soil exposuresaround settlements (Canaan, 1932e33; Dalman, 1928e42;Mcintosh, 1974). Once collected, the raw material is manipulatedby sorting, sieving, and mixing with materials such as sand, straw,dung or gravel in order to improve the mechanical strength of themud brick (Rosen, 1986; Torraca et al., 1972). The resulting sedi-ment is then mixed with water and put into a wooden mold whichis lifted and the wet brick is left to dry (Canaan, 1932e33; Koulidou,1998; Spencer, 1979).

Sun-dried mud bricks inevitably degrade because the earthenmaterial of which they are composed reacts with the environment.Previous research points out that the major agent in the degrada-tion process of mud bricks is water from rain and/or rising dampand it introduces soluble salts into the earthen material whichcause swelling and splitting of bricks upon dehydration (Carter andPagliero, 1966; Mcintosh, 1974; Torraca et al., 1972). The degrada-tion process of mud brick walls is also affected by wind erosion(Carter and Pagliero, 1966), biological activities such as penetrationof plant roots, bird nesting within mud brick walls, and burrowingby rodents and insects (Goodman-Elgar, 2008; Torraca et al., 1972).After abandonment, the degraded brick material accumulates onthe regional sediment outside the house, or on the floor inside thehouse. This accumulated brick material usually cannot be distin-guished by the naked eye from the regional sediments. In archae-ology, this results in problems of field interpretation and inability totrace the contours of long-degraded mud walls.

Pioneering ethnographic observations onmudwall decay and anexcavation of modern decaying mud structures in West Africa wereconducted by McIntosh in the 1970s (1974; 1977). McIntosh (1974)observed that rain splash and capillary movement of salt-contain-ing water at wall bases caused undercutting of the lower part of themud walls. This process lead to outward wall collapse. In addition,he observed that degradedbrickmaterial accumulated onboth sidesof the degrading walls sometimes forming thin films of sediment.Most other studies of mud bricks focused on particle-size analysis(i.e., granulometry) in order to investigate the properties of varioustypes of sediments, their composition, selection of rawmaterial, andsourcing of the mud brick material (Davidson, 1973; Emery andMorgenstein, 2007; Goldberg, 1979; Kemp, 2000; Nodarou et al.,2008).

Only two geoarchaeological studies touch upon the issue of mudbrick degradation. Koulidou (1998) excavated two abandonedmodern mud structures in Northern Greece in order to investigatethe depositional patterns of mud wall degradation using particle-size analysis. She noted a reduction of the grain sizes within the fillsediments toward the center of the studied room (Koulidou, 1998).The second study was conducted by Goodman-Elgar (2008) whoexamined the degradation of abandoned earthen dwellings inBolivia through micromorphological analysis. Goodman-Elgar’smicromorphological work enabled her to identify accumulation oforganic matter, burnt sediment, building material and to identifypost-depositional processes such as bioturbation (Goodman-Elgar,2008). The studies by Koulidou (1998) and Goodman-Elgar (2008)were pioneering, but used only one technique each (particle-sizeanalysis and micromorphology, respectively).

Herewe present geoarchaeological research that was conductedat a pre-modern abandoned mud house e hereafter referred to as

the Gvulot mud house e in order to gain more insights into theprocesses involved in mud brick degradation, the resulting “mud-brick material”, and the mixing of degraded brick material withregional sediments and the house floor. Overall we present a modelof mud brick house degradation, fromwalls to infill sedimentation.The study area is within an arid environment as such environmentsprevail throughout the Near East. Future research will focus onwetter environments.

1.2. The study area

The mud house chosen for this study is located near KibbutzGvulot in the northern part of the western Negev, Israel (the Besorarea; Fig. 1). The climate in this area is semi-arid, with an average of150e200 mm of rain per year (Bitan-Buttenwieser, 1967). The rainyseason is short (usually October to March) and rain showers areusually brief but strong. The topography slopes gently fromwest toeast at 60e160 m above sea level.

The Gvulot mud house was built by Bedouins (nomadic pasto-ralists), who settled in the region during the 19th and early 20thcenturies, under the Ottoman and the British mandatory regimes. Inthe first half of the 19th century large populations of Egyptian peas-ants and Bedouins migrated from the Sinai Peninsula to the Besorregion encouraged by the economical relationships between theagricultural farms of the area with the city of Gaza. During the 19thcentury the tribal conflicts in the area diminished under the Ottomanregime contributing to stability of agricultural farms. The OttomanSultans encouraged the nomadic Bedouins to settle down, gave themrights to cultivate the land and helped in designing their newsettlements (Gazit, 2000). Due to the encouraged sedentarization ofthe Bedouins, their farm houses had an architectural plan similar tothat of the black tent. These houses included a living sectioncomposed of two rooms, one for the men and the other for thewomen (Gazit, 1986). They were built frommud bricks, did not haveany windows, and the roof was flat andmade from a braid of vegetalstems (e.g., dry reeds, palm leaves, thorn bushes, or cornstalks) andwooden beams. This vegetal braid was covered by mud mixed withstraw (Canaan, 1932e33; Gazit, 1986). In front of the rooms a rect-angular yard was built surrounded by low walls of bricks or stone(Gazit, 1986).

The mud house chosen for this study was identified by localarchaeologist Dan Gazit, who also attributed it to the early 20thcentury based on the geographic history of the region, the archi-tecture of the house and the abundance of blackegray Gaza Waresherds typical of the local Bedouin material culture at the 19th andearly 20th centuries (Gazit, 1986). The Gvulotmud house, likemanyother Bedouin houses in the region, was abandoned in 1948 as theBesor area suffered from the outcomes of war between Egypt andIsrael. Since the early 1950s the region has been used by the Israeliarmy for training. The studied mud house was left to decay, withminor human activity in its vicinity.

2. Materials and methods

2.1. Fieldwork strategy

The research included a small-scale excavation in the aban-doned Gvulot mud house.

The housewasmapped using a hand-held GPS (Garmin eTrex H)by UTM coordinates and height above sea level, accompanied bymeasuring each feature noticeable in the field using a tape. Thestudy areawas divided into a 1�1m grid and two 1mwide paralleltrenches were opened, traversing the house along its width (ona northesouth axis, Fig. 2a). Trench H traversed the roofed areawhile Trench K traversed the open courtyard area. The trenches

Fig. 1. Map showing the general location of Gvulot in southern Israel, and a photograph showing the mud house before excavation (April 2008). Length of wall in the background isca. 8 m.

D. Friesem et al. / Journal of Archaeological Science 38 (2011) 1135e1147 1137

were dug to a depth of a few centimeters below the presumedhouse floor.

Continuous systematic sediment sampling was conducted, inwhich samples were taken from a column, one above the other.Selective sampling was employed on specific features of interestwhen a specific question arose in the field (Courty et al., 1989). Thesamples were collected according to sediment color, texture andhardness. Control sediments (i.e., regional sediments) were sampledoutside the site. The local soil was sampled in a pit excavated ca.50 m east of the site. Wind blown sand dune sediments weresampled in excavated pits ca. 200 m south and ca. 500 m west ofthe site. Bulk samples were registered with running numbers andput in plastic vials using a metal spoon. Undisturbed blocks for

Fig. 2. Drawing of the excavated mud house. (a) Above ground features before exca-vation, showing the placement of trenches, one within the roofed area (western part ofthe structure) and one within the courtyard area (eastern part of the structure).(b) Above and below ground features following the excavation, showing the depth ofwalls, erecting the fallen walls, and extrapolating the extent of the house floor.

micromorphological analysis were sampled selectively based oncontextual considerations.

2.2. Laboratory techniques

Bulk samples were analyzed using FTIR spectroscopy and X-RayFluorescence (XRF) spectrometry, the former in order to identifyorganic and mineral components and the latter in order to searchfor patterns using chemical elements. Representative FTIR spectrawere obtained from all samples (n ¼ 112) by grinding a few tens ofmicrograms of sample using an agate mortar and pestle. About0.1 mg or less of the samplewasmixed with about 80mg of KBr (IR-grade). A 7 mm pellet was then made using a hand press. Thespectra were collected between 4000 and 250 cm�1 at 4 cm�1

resolution using a Thermo Nicolet 380 spectrometer and inter-preted using an internal library of infrared spectra of archaeologicalmaterials (Weiner, 2010).

Quantitative bulk chemical compositions were obtained by Ene-rgy Dispersive X-Ray Fluorescence (ED-XRF), using a Spectro-XEPOSbench-top instrument, with a Palladium (Pd) anode equipped witha series of secondary targets. Evaluationof resultswasdoneusing theXEPOS method for powder materials. Fifty-eight representativesediment samples were analyzed. Approximately 3 g of sedimentwere lightly homogenized using a mortar and pestle. The measure-ments were taken in an air environment. Under these conditions,elements with an atomic mass lower than aluminum could not bemeasured. Results are presented as percentage by weight (wt%) ofthe element’s oxide form.Measurements were conducted in batchesof 12, from which one sample was a Certified Reference Material(CRM): GSS-1; Geological Soil Sample (also called GBW-07401)produced by the Institute of Geophysical and Geochemical Explora-tion (IGGE), Ministry of Geology, and the Institute of Rock andMineral Analysis (IRMA) in China. The elemental nominal values ofthe GSS-1 standard were compared to the results obtained from thestandard in each batch of measurements conducted in this study. Inorder to test the reproducibility and to estimate the error of themeasurements, 2 archaeological samples as well as the standard(GSS-1) were measured in triplicates. Upon analysis of the results, itbecame clear that only 4 of themeasured elementswere informativefor this study (Al, Si, Ca, Fee see Results section). The reproducibilityof the measurements for these 4 informative elements is better than10% (Table 1).

Table 1XRF results of the standard, triplicate and sedimentological groups studied. Values and averages are reported inwt%. Coefficient of variation (CV) is calculated as the percentageof the standard deviation from the average value. Note that the analytical sum is always lower than 100% due to presence of unmeasured light elements. The results are thusreported without correction or normalization.

Sample Al2O3 SiO2 CaO Fe2O3 Sum of analysis

GSS-1 nominal values 14.18 62.6 1.72 6.6GSS-1 measured values (n ¼ 6) Average 17.56 63.14 2.04 5.68 92.86

Std 0.81 2.45 0.01 0.02 3.31CV 4.59 3.89 0.50 0.35 3.56

Archaeological sediments triplicates Mud brick Average 9.90 39.07 17.02 4.16 73.20Std 0.10 1.64 0.99 0.24 0.73CV 1.03 4.19 5.82 5.72 1.00

Infill sediment Average 9.35 59.80 5.10 1.65 77.98Std 0.15 2.26 0.48 0.14 1.62CV 1.65 3.78 9.36 8.67 2.08

Control e Wind blown sediment (n ¼ 5) Average 9.09 59.17 5.43 1.59 77.32Std 0.49 7.35 1.65 0.39 5.24CV 5.35 12.41 30.37 24.67 6.78

Control e Husmas soil (n ¼ 1) 7.71 30.96 17.20 3.34 61.26Control e Nahal HaBesor sediment (n ¼ 1) 5.71 19.84 14.10 4.71 46.28Control e Mud bricks (n ¼ 6) Average 9.81 37.40 12.75 4.25 66.86

Std 0.87 3.82 1.74 0.64 3.08CV 8.87 10.22 13.62 15.01 4.60

White layer (house floor) (n ¼ 5) Average 3.61 21.78 26.11 1.79 54.87Std 1.02 5.66 4.33 0.23 3.20CV 28.35 25.99 16.58 12.71 5.83

Yellow infill sediment (n ¼ 12) Average 8.99 55.15 7.06 1.70 74.97Std 0.73 8.54 3.18 0.25 5.83CV 8.13 15.49 45.09 14.80 7.78

Yellowegray infill sediment (n ¼ 5) Average 9.18 51.19 7.56 2.43 72.53Std 0.65 9.06 2.87 0.81 5.72CV 7.08 17.70 38.01 33.24 7.89

Gray infill sediment (n ¼ 8) Average 9.08 40.21 11.26 3.27 66.21Std 0.89 8.04 3.31 0.63 6.10CV 9.85 19.99 29.37 19.26 9.22

Brown infill sediment (n ¼ 6) Average 9.86 36.75 12.41 4.49 54.98Std 0.56 2.56 1.63 0.44 2.13CV 5.71 6.97 13.13 9.81 3.87

Gray infill sediment above white layer (n ¼ 6) Average 6.79 28.57 13.73 3.79 54.98Std 0.80 1.71 1.33 0.48 2.13CV 11.85 5.98 9.67 12.78 3.87

D. Friesem et al. / Journal of Archaeological Science 38 (2011) 1135e11471138

Since the 58 sediment samples were measured only once, anaverage and a standard deviation could not be obtained per sample,but as samples generally belong to various sedimentological groups(see results section below), such values can be calculated per sedi-mentological group (i.e., average and standard deviation of eachsedimentological group). The standard deviations calculated persedimentological group are generally larger compared to the stan-dard deviations of the experimental triplicates, and those betweenthe nominal and measured values of the standard, reflecting thenatural heterogeneity of the sediments (Table 1). Note that theanalytical sum of measured elements in the various sedimentolog-ical groups is less than 100%, but that the standard deviation of thesum of analyses per sedimentological group is low (Table 1). Theseobservations indicate that the low values of sum of analysis do notreflect the quality of the analyses but the presence of light elementsin the sediments. Results are thus reported without correction ornormalization.

Undisturbed monolithic sediment blocks were prepared for mic-romorphological analysis following conventional procedures (Courtyet al., 1989). The blocks were dried in an oven at 50 �C for three daysand then impregnated using a 9:1 mixture of polyester resin andacetone. Pre-cut sample slices were prepared to 30 mm thickness,2 � 3 inch, thin sections by a commercial company (Quality ThinSections, Tucson, Arizona). The prepared thin sections (n ¼ 19) werestudied using polarizing light microscopes (Nikon Labophot2-LOPandNikonEclipse50iPOL) at variousmagnifications (20�, 40�,100�,200� and 400�). Micromorphological descriptions employ theterminology of Bullock et al. (1985) and Stoops (2003).

3. Results: macroscopic field observations

3.1. House location, shape and size

The Gvulot mud house is located at 36-640-135 E/34-510-049 Nin UTM coordinates, 2.5 km south of Kibutz Gvulot, and 147m abovesea level. The house has a rectangular shape, oriented on a north-westesoutheast axis. For simplicity, cardinal directions will be usedthroughout the text, whereas the longerwalls (forming the length ofthe rectangle) are the north and south ones, and the shorter walls(forming the width of the rectangle) are the east and west ones.

Thehouse includes two clearwalled spaces. BasedonGazit (1986;personal communication, 2009) and on the height of preservedwalls, the larger space (ca. 9 � 8.5 m) on the east is interpreted asa courtyard, and the smaller space (ca. 5 � 8.5 m) on the west isinterpreted as the roofed living quarters. No doorways have beenidentified. According to Gazit (1986) the roofed area should includetwo separate rooms, however the excavation in Trench H did not cutthrough a separating brick wall. It is possible that in the studiedhouse the division between men and women quarters was made bya screen such as cloth or vegetal material, which is not expected toleave a visible trace after degradation. It is also possible that a thinmud-brickwall existed, not traversed by the excavation if it parallelsone of the baulks that were left standing during the excavation.

The house and close area surrounding it is slightly elevatedrelative to the general surroundings, forming a minor tell. Moresedimentaccumulated inside thewalled area thanoutside thehouse,i.e., the house serves as a “dust trap”. In addition, more sediment

Fig. 3. Macroscopic mechanisms of mud brick wall degradation in the study area.(a) Disintegration and collapse of single bricks. (b) Collapse of intact wall partsoutwards. (c) Collapse of intact wall parts inwards, and their subsequent burialunder infill sediments. Scale bar ¼ 20 cm.

D. Friesem et al. / Journal of Archaeological Science 38 (2011) 1135e1147 1139

accumulated in the roofed area relative to the courtyard, indicatingthat more wall material was present in the roofed area.

3.2. Brick description and wall preservation

The mud bricks in the site are ca. 33 � 19 � 17 cm. They arecomposed of brown (Munsell dry: 10YR 5/3e6/3) hard sediment,including visible straw fragments and/or straw voids. The twotrenches opened during field work cut through and next to thesouthern and northern walls at four points, revealing the depth towhich the walls were built. This depth accords with a horizontalcalcareous layer interpreted as the house floor, which furtherallows extrapolating the height of walls below surface around thehouse also in the unexcavated parts (Fig. 2b).

The preservation of the mud brick walls varies around the site.Where someof thewalls preserved to a considerable height (close to2 m above surface), others had degraded so much that nothing isvisible on the surface except for a minor elevated sediment heap.Wall disintegration seems to occur by two mechanisms: the first isthe disintegration of single bricks (Fig. 3a) and the second is collapseof intact wall parts either outwards (Fig. 3b) or inwards (Fig. 3c). Athird, microscopic, degradation mechanism was observed withinthe house infill sediments (see details below).

3.3. Regional sediments and soils

Three different types of regional sediments were identified andsampled in the vicinity of the site:

A) Wind blown sediments: Yellow (Munsell dry: 10YR 7/4e7/6)loose dune sand, covering the landscape surface and reachinga depth of ca. 30 cm below surface. These sandy sedimentsoriginate from stabilized Pleistocene dunes that are covered byeolian shifting sands (Dan et al., 2007).

B) Husmas soil: Husmas is a local name for a red sandy soil withcalcareous concentrations (Calcic Rhodoxeralf) formed oneither calcareous eolianite sandstones (locally known as Kur-kar) or on sanddunes,most frequently found in the coastal plainof southern Israel (Singer, 2007). This paleosol was identified inthe study area in a test pit excavated 15 m east of the site. It isa brown (Munsell dry: 10YR 7/3) hard loam with white calcar-eous nodules whose concentration increases with depth.

C) Alluvial sediments: The closest alluvial channel to the studyarea is Nahal HaBesor. It is a perennial stream that currentlydrains sewage. About 6 km northeast of the site the stream isclosest to the abandoned house. HaBesor riverbed sediment isbrown (Munsell dry: 10YR 4/3) loam.

3.4. House infill sediments

The excavation in both trenches revealed 4 main types of sedi-ments (Fig. 4). The lowermost sediment in both trenches is white(Munsell dry: 10YR 8/1e8/4) and its upper surface as exposed in theexcavated trenches is semi-horizontal. The local bedrock and soil donot exhibit these characteristics. Therefore this sediment is eitherlocal calcareous bedrock that we did not encounter outside the sitethat was cut flat for the purposes of the house building, or non-localsediment that was brought to the site for construction purposes. Inany case, because its color and texture differ markedly from theregionalwindblown sediment and because Bedouin artifacts (metalobjects aswell as GazaWare pottery)were found lying just on top ofit, this white surface is interpreted as the house’s floor.

Three main types of infill sediments were identified above thewhite floor. The infill sediments are bedded and alternate randomly.

They include artifacts that are assigned to the Israeli army training inthe area after 1948 (e.g., metal cans and barrels, plastic bags, etc.).The infill sediment types are (Fig. 4):

A) Yellow sandy loose sediment, similar to the local wind blownsediments. This sediment is found in the house infill as patchesand layers between other sediment types in the excavatedareas and on the surface.

B) Gray (Munsell dry: 10YR 7/1e7/3) soft and hard, loamy sedi-ments. These sediments accumulated inside the house as thinlaminae. Despite their gray color, no ash was observed associ-ated with these infill sediments.

C) Brown hard loamy sediment (Munsell dry: 10YR 5/3e6/3),mostly adjacent to the inner part of the walls. This sediment issimilar macroscopically (based on color and compactness) tothe house’s mud bricks. During the excavation several bricks

Fig. 5. Plots showing sediment accumulation patterns within the trench that traversesthe roofed area. (a) Thickness of sediment types along three columns in the trench, oneclose to the southern wall, one close to the north wall, and one in between the othertwo in the center of the roofed area. Note that the total thickness of all sediments issimilar in the three columns, forming a semi-horizontal surface. (b) Cumulativethickness in the three columns according to sedimentological groups showing thatbrown sediments are thicker next to walls and thinnest in the central area while thegray sediments are thickest in the center and thinner next to walls. At the same time,the yellow sediments show a rather uniform thickness along the studied section. (Forinterpretation of the references to color in this figure legend, the reader is referred tothe web version of this article.)

Fig. 4. Photograph showing the main sedimentological groups at Gvulot mud house.(a) White horizontal homogenous surface interpreted as the house floor. (b) Massivebrown. (c) Yellow soft sandy sediment interpreted as originating from wind blowndust and (d) Gray laminated sediments, interpreted as originating from decayed mudbricks. Scale bar ¼ 20 cm. (For interpretation of the references to color in this figurelegend, the reader is referred to the web version of this article.)

D. Friesem et al. / Journal of Archaeological Science 38 (2011) 1135e11471140

were exposed far from the walls after they fell and rolledtoward the center of the house.

Various shades of gray have been identified in the field anddescribed as yellowegray, grayebrown, and black sediments.

3.5. General infill sedimentation patterns

The thickness of the three main types of infill sediments wasmeasured inthe trench in the roofedarea.Thicknessesweremeasuredalong three columns arbitrarily chosen on the eastern section of thetrench, one close to the southernwall, one in themiddle of the roofedspace and one close to the northern wall. All measurements wereconducted relative to the topmost level of the white layer (Fig. 5a).

The cumulative thickness of each infill sediment type, above thefloor level is presented in Fig. 5b. The yellow wind blown sedimentdoes not change significantly across the three columns, with a rangeof 25e29 cm, indicating an even distribution across the space. Aninverse relationship is found for the grayand brown infill sediments.While near the walls the thickness of the gray infill sediment is low,the thickness of the brown infill sediment is highest.

3.6. Biological activity within the sediments

At the macroscopic scale, arthropods (e.g., beetles, spiders, scor-pions, etc.), rodents, snakes and gazelleswere observed either on siteor in its vicinity during the oneweek of excavation. In addition to thefauna, plants and their roots are abundant in and around the site.Another biological activity, that had a most significant impact on thesite’s integrity, is the post-abandonment soldier activity. The soldiersseem to have camped at the site, based on the refuse related to foodand other activities. Even though it cannot be proven, the soldiersmay have deliberately brought down parts of walls and the roof.

4. Results: laboratory-based analyses of the sediments

4.1. Mineralogical characterization of bulk samples via FTIRspectroscopy

Based on their infrared spectra, sediments in the study areaare rather similar mineralogically, being composed of quartz, clayand calcite in various ratios. Sediments sampled around the site

(i.e., control samples) include soft yellow (Munsell dry: 10YR7/4e7/6) wind blown sandy sediment. The major mineral compo-nent in this sediment is quartz, followed by clay and small amountsof calcite (Fig. 6a). Compacted yellow sandy sediments found a fewcm below surface have a similar composition as the soft sandysediments. Crusts on top of sandy deposits are composed mainly ofclay and quartz. Below surface, compacted dune sands includewhite nodules and these sediments are dominated by calcite. Theyseem to correspond with the local Husmas soil, having varyingamounts of clay and calcite according to depth (Fig. 6b). Lastly, thealluvial sediment from Nahal HaBesor riverbed is composed mainlyof clay and calcite, and traces of quartz.

Controls from within the site are in the form of the mud bricksthemselves. Based on the infrared analyses, mud bricks from thestudiedhouseare composedprimarilyof clay, followedbycalcite anda small amount of quartz (Fig. 6c). Note the similarity in mineral-ogical composition between the mud brick and local Husmas.

The infill sedimentswithin the site are generally yellow, gray andbrown (see Section 3.4 above). The yellow infill sediments aredominated by quartz (Fig. 6d) and their mineralogy resembles thatof the wind blown regional sediments. The brown and gray infillsediments are composed of high amounts of clay, followed bycalciteand a small amount of quartz (Fig. 6e). This mineralogical compo-sition is similar to that of the control mud bricks (c.f., Fig. 6c) andHusmas soil (c.f., Fig. 6b). The white sediment layer that was

Fig. 6. Infrared spectra of representative sediment samples in the study area. (a) Control, yellow wind blown sediment, (b) Control, Husmas local soil, (c) Control, mud brick, (d)Yellow infill sediment, (e) brown/gray infill sediment, (f) white floor sediment. Note the similarity between spectra (a) and (d) where the sediment is dominated by quartz(indicative absorptions at ca. 1086, 517, 798, 778 and 695 cm�1); the similarity between spectra (b), (c) and (e) where the sediment is dominated by clay (indicative absorptions at ca.1035, 913, 798, 778 and 530 cm�1); and the significantly different spectrum (f) where the dominant mineral is calcite (indicative absorptions at ca. 1430, 875 and 713 cm�1).

D. Friesem et al. / Journal of Archaeological Science 38 (2011) 1135e1147 1141

identified as the house floor is composed primarily of calcite, fol-lowed by clay and trace of quartz (Fig. 6f). In comparison to thecontrol sample of the Husmas soil outside the site, it has a signifi-cantly higher concentrationof calcite and rather lowamounts of clayminerals. No infill sediments resemble themineralogical fingerprintof the white floor layer. The grayeyellow infill sediments showeitherhighquartz orhigh claycomponents, i.e., hinting for amixtureof sedimentary sources. Overall, all the sediments in the archaeo-logical context coincide with three main mineralogical groups,differentiated by the ratios between quartz, calcite and clay, andmineralogical similarities seem to indicate the source of some ofthese infill sediments (Table 2).

4.2. Elemental characterization of bulk samples via X-RayFluorescence (XRF) spectrometry

A total of 58 control and infill sediments were measured in 6different batches. The results were plotted in order to search for

Table 2The correspondence between mineralogical groups (based on infrared spectroscopyresults) and sedimentological groups (based on macroscopic field observations) inthe studied site. The dominant mineral in each group is marked in bold, followed bythe other minerals in order of dominance.

Mineralogical groups Sedimentological groups

Quartz > clay > calcite Regional wind blown sedimentYellow infill sediment

Clay > calcite > quartz Grayeyellow infill sedimenta

Gray infill sedimentBrown infill sedimentMud brick materialHusmas paleosol

Calcite > clay > quartz White floor

a This sedimentological group has variable mineralogy, dependent on the amountof clay (more gray) and quartz (more yellow).

meaningful patterns. The concentrations of most elements werevery low, thus when considering the analytical error, no clearpatterns were revealed using these elements. On the other hand, 4major elements e aluminum (Al), silicon (Si), calcium (Ca) and iron(Fe) e showed significant patterns in relation to the sedimento-logical groups at the site (Table 1).

Fig. 7a shows a significant difference in the elemental composi-tion of the white floor layer compared to most other sediments. Asseen fromthe infrared spectra thewhite layer ismainly composed ofcalcite, with a low amount of clay and quartz, which explains itsrelative richness in lime (CaO) and relative low amounts of alumina(Al2O3), silica (SiO2) and iron oxide (Fe2O3); the latter relate to clayand quartz. The composition of the major elements in the Husmassoil seems to be close to the group of dark-colored (brown and gray)infill sediments and mud bricks. This was also observed in theinfrared spectra of these infill and control sediments. The sedimentcollected fromNahal HaBesor riverbed does not seem to correspondclearly to any of the sedimentological groups, having alumina andsilica concentrationsmost similar to thewhite layer and at the sametime lime and iron oxide concentrations most similar to the dark-colored infill sediments and mud bricks. This may be related to thefact that this river currently drains sewage. Alternatively, it mayindicate that this sediment does not play a significant role in theGvulot house sedimentological system. Its elemental compositionwill thus not be discussed further.

The difference between the various infill sediments is clearest inthe concentration of silica, where yellow-colored sediments havehigher values than darker-colored sediments. This difference seemsto correspond to the presence of higher amounts of quartz in theyellow sediments as is also reflected in their infrared spectra. Thedarker-colored sediments include more clay than the yellow-colored sediments, based on their infrared spectra. This explains thedifference in concentrations of alumina and iron oxide betweenthese general sedimentological groups, with the darker-colored

Fig. 7. Plots showing elemental compositions for the sedimentary groups in the study area. (a) Average concentrations (wt%) of the oxides of aluminum, silicon, calcium and iron.Error bars indicate the standard deviation where more than one sample has been analyzed from the same sedimentological group. Note that in most cases there are distinctivesimilarities between Husmas soil, mud bricks and brown/gray infill sediments; between yellow control and infill sediments, and that the yellow sediments are different significantlyfrom the Husmas and brick sediments. Note also that the white floor sediment is distinctively different from all other sediment types. (b) The relationship between concentrationsof alumina and iron oxide, showing two distinct mixing lines that explain the variability observed in the infill sediments. Here the gray infill sediment samples are divided into graysediment that was sampled along the profile (n ¼ 8) and gray sediment that was sampled directly above the white floor (n ¼ 6). The latter is shown here with white asterisk insidea gray square. (1) mixing between mud brick material and yellow wind blown sediments, resulting in gray infill sediments; (2) mixing between mud brick material and the whitefloor sediment, resulting in another type of gray infill sediments. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of thisarticle.)

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sediments generally having higher concentrations of alumina andiron oxide relative to yellow-colored sediments. The concentrationof limealso seems todistinguish theyellow-colored fromthedarker-colored sediments,with the latter havingmore lime. This is probablyrelated to the presence of calcite (also reflected in the infraredspectra of these sediments) and also possibly to the presence ofCa-montmorillonite in these sediments. Indeed, the highly calciticHusmas and white layer have the highest lime concentrations.

Based on field observations and the infrared results, threematerials seem to be the origins of the archaeological infill sedi-ments at the site; the yellowwind blown sediment, the lowerwhitelayer and the mud bricks. This is also reflected in the elementalcomposition of the sediments, best shown through the relationshipbetween the concentrations of alumina and iron oxide (Fig. 7b). Themud bricks, the control wind blown sediments and the white floorlayer seem to form end-members. The mixture of these end-members shows graphically as mixing lines (Fig. 7b): the yellowwind blown infill sediment cannot be distinguished from thecontrol regional wind blown sediment, indicating that the yellowinfill sediments originate from wind blown dust. The brown sedi-ment shows high similarity to the mud bricks, indicating that it isa direct product of mud-brick degradation, with virtually nomixingwith wind blown dust. The elemental composition of the gray infillsediments sampled just above the white floor is in the rangebetween the mud bricks and the lower white layer, indicating theirorigin is from degrading mud bricks mixed with the white sedi-ment, while the gray and yellowegray infill sediments in othercontexts at the site show that they originate from a mixturebetween mud bricks and yellow wind blown sediments.

The Husmas soil in the site’s area has low iron oxide concen-tration relative to most mud bricks, and also slightly less alumina.This indicates that this soil is either not the source of the mudbricks, or, that it is one of the sources. Support for the secondpossibility is found in the micromorphological results (see belowSection 4.3.1). In addition, it is possible that the source materials forthe preparation of the mud bricks have been manipulated by thebuilders, thus changing the original composition of the local Hus-mas. For example, the concentration of lime in the mud bricks

is much lower than in the sampled Husmas, implying that if theHusmas was used by the builders they probably lowered theamount of lime by removing large calcitic white nodules from thissoil. If true, this would have contributed to the higher relativecontent of silica in the mud bricks.

Overall the elemental analysis supports and amplifies the fieldobservations and the attribution of the sediments to the differentsedimentological and mineralogical groups.

4.3. Micromorphology

The basic components observed in thin section follow the sametrends identified in the studied sediments based on the FTIR andXRF analyses. Table 3 presents the overall composition and sedi-mentological attributes (e.g., grain sizes, roundness and sorting) ofthe studied sedimentological groups. These attributes show thesimilarity between control wind blown and yellow infill sediments,between the Husmas control and mud bricks, and between themud bricks and brown and gray infill sediments. The white floorlayer differs from all infill sediments.

Micromorphological differences between the sedimentologicalgroups are best expressed by the void types and overall micro-structure. Wind blown sediments are composed of a coarse fractionwithout groundmass, therefore their microstructure is single-grainand voids are simple packing voids (Fig. 8a). The white floor sedi-ment is massive and includes vertical desiccation cracks (Fig. 8b). Itis difficult to determine, microscopically, whether this sediment isundisturbed calcareous bedrock or crushed and compacted calcar-eous rock brought to the site on purpose. The Husmas soil includeschamber, vesicle and channel voids within a complex microstruc-ture including vughy and massive microstructures (Fig. 8c). Thevoids together with snail shell fragments and thin clay coatings oncoarse grains indicate bioturbation. Overall, the Husmas soil seemsto have developed mostly from accumulation of eolian sediments,with little pedogenic processes due to the relative aridity at thestudy area. The presence of quartz grains larger than medium sand(Table 3), i.e., grains that could not have been deposited throughwind action, might be either inherited from the parent rock below

Table 3Basic micromorphological attributes in the studied sediments (based on analysis of 19 thin sections).

Coarse fraction Fine fraction Relateddistributiona

Void types

Minerals/Grains Grain Sizes Groundmass BirefringenceFabric

Wind blown controls Quartz, well sorted, subangular Silt-fine sand None None Monic Simple packingYellow infill sediment Calcite Fine sand

Shells Fine sandHusmas control Quartz, poorly sorted, subangular

FeldsparHornblende

Silt-coarse sand Calcitic-clay Crystallitic Monic Vughs, vesicles

Calcite nodules, orthic and anorthicb Very fine-medium sandShells Medium-coarse sandOxides Silt-very fine sand

Mud brick (control) Quartz, poorly sorted, subangularFeldsparHornblendeFlint

Silt-coarse sand Calcitic-clay Crystallitic Porphyric Vughs, vesicles, planar

Brown and Gray infillsediments

Calcite, sparitic and/or micritic,poorly sorted, subrounded

Silt-coarse sand Calcitic-clay Crystallitic Porphyric Vughs, vesicles

Shells Coarse sandOxides Silt-fine sandClay-rich aggregates, poorly sorted,subrounded

Fine-medium sand

White floor layer Quartz, poorly sorted, subangular Silt-medium sand Calcite Porphyric Porphyric Desiccation cracks

a Monic related distribution: only grains of coarse fraction are present; Porphyric related distribution: the coarse fraction occurs in a dense groundmass of fine fraction(Stoops, 2003).

b Nodular bodies inherited from the parent material are termed anorthic, while those formed in situ are termed orthic (Stoops, 2003).

Fig. 8. Microphotographs of representative control samples in thin section, all in plane polarized light. (a) Wind blown yellow sediments. Note the near absence of fine fractionresulting in a single-grain microstructure. (b) White floor layer (in the lower part of the photograph) showing a massive microstructure and vertical desiccation cracks. The upperpart is wind blown sediment. (c) Husmas sandy soil with complex microstructure and evidence of bioturbation. (d) Control mud brick showing features generally similar to those inthe Husmas soil, but with planar voids with/without straw temper and with rounded clay-rich granules. (For interpretation of the references to color in this figure legend, the readeris referred to the web version of this article.)

D. Friesem et al. / Journal of Archaeological Science 38 (2011) 1135e1147 1143

D. Friesem et al. / Journal of Archaeological Science 38 (2011) 1135e11471144

the Husmas (possibly stabilized coastal dunes) or from mild sheet-wash erosion in the studyarea. The description and interpretation ofthe Husmas is in accord with Singer (2007).

The basic components in mud bricks (observed in 5 differentthin sections) are similar to those in the Husmas soil (Table 3)except for presence of clay-rich aggregates with or without micriticcalcite and silt to fine sand quartz grains (Fig. 8d). These clay-richaggregates may have originated from alluvial sediments. Theyclearly do not form an integral part of the soil fabric. The void typesare similar between the Husmas and mud bricks except for thepresence of planar voids in mud bricks. The elongated planarvoids resemble the shape of straw and lie in different orientations.In some of these voids the straw is present in different stages ofdecomposition. Phytoliths, parallelepiped elongated long cellsindicative of grass leaf/stem origin, were observed within thesevoids (Fig. 8d). The microstructure is complex, including massiveand vughy microstructures. Some of the coarse fraction grains areclay coated, in a thicker layer than the thin clay coating in theHusmas paleosol. The overall micromorphological features of themud bricks indicate that the bricks might have been prepared froma mixture of local Husmas with alluvial clay-rich sediments(possibly from the nearby Nahal HaBesor stream) and grass strawas temper.

The basic components in the brown and gray infill sediments aresimilar to those of mud bricks (Table 3). The main differencesbetween the original mud brick sediment and the brown and grayinfill sediments are: (1) the absence of the vegetal temper (straw), orits indicative planar voids, (2) infilling of voids with micritic calcite,(3) formation of dirty calcitic-clay crusts, and (4) formation of pureclay crusts (Fig. 9a). All these features are attributed to the degra-dation process of the mud bricks and this micromorphologicalsedimentary facies relates to the brown and, in a more progressedstage of degradation, to the gray sediments macroscopically iden-tified at the site.

4.3.1. Depositional processesWithinageneral regimeofwindblown infill sedimentation, bands

of medium quartz sandwere observed associated with the gray infillsediment (Fig. 9b). Such large grains could not have been depositedthrough eolian processes, indicating that small-scale changes in theforces of deposition took place at the site, shifting betweenwind andpossibly water or gravity flow depositional patterns.

4.3.2. Post-depositional processesIn all infill sediments, channel voids indicative of faunal move-

ment through the sediment cut through layers of the differentsedimentological groups. Fresh organic excrements (identifiedfollowing photographs in Stoops, 2003) were identified in voids inthe infill sediments. Bioturbation, as well as water and wind actionat the site resulted in the mixing of the different sedimentologicalgroups. One observation is that at the contact between the lowerwhite layer and the sediments on top of it there are areas where thesharp contact that characterizes this sedimentological transition issometimes obscured by penetration of either the white sedimentupwards into the gray or yellow infill, or of the gray/yellow infilldownwards along cracks and channels into thewhite layer (Fig. 8b).

The early stages of mud brick degradation were observed ina specific area where mud brick fragments degrade in situ, showingthe formation of calcitic-clay crusts around the fragments’ edges(Fig. 9c). The later stage in mud brick degradation is characterizedby the formation of calcitic-clay crusts, occasionally with silt to finesand grains within them, related to slow water movement in theform of a slurry gravity flow. In certain locations, weak gradedbedding hints for the presence of occasional puddles where crustsof pure clay accumulated above a calcitic-clayey crust that includes

fine sand to silt grains (Fig. 9b). The final stage of the process showsthat these crusts break and their orientations change followingbioturbation within the infill sediments (Fig. 9d).

Overall, the micromorphological observations enable us toidentify the source materials of the mud bricks to a certain degree,to evaluate the role of bioturbation at the site, and most impor-tantly, to identify the processes involved in mud brick degradationand formation of the house infill sediments.

5. Discussion

The overall aim of this study was to understand the processesrelated to mud brick degradation and formation of infill sedimentswithin abandoned houses in an arid environment. The results of thisstudywill help in developing amethod for accurate identification of“mud-brick material” in archaeological sites in the Near East.

5.1. Sedimentary sources at Gvulot mud house

The sediments forming the infill at Gvulot mud house wereidentified based primarily on mineralogical (FTIR) and elemental(XRF) analyses. The use of these techniques in conjunction enablesus to not only identify source materials, but also mixtures betweenthem. Themajor sources of the infill sedimentswere degradingmudbricks and wind blown sediment. The large volume of wind blownsediments is probably typical of arid environments, and should beconsidered in anygeoarchaeological study of formationprocesses insimilar sites. The house floor is a third, butminor, sourcematerial, asindicated by the mixing lines observed following the XRF analysis(Fig. 7).

The infill sediments include the source materials and alsomixtures between them in various ratios, thus exhibiting a range ofcolors, hardness, texture, mineralogy and elemental compositionsthat are wider than the range of the sources themselves. Clearly,due to differences in mud brick recipes in different sites, the valuesreported in this study should not be taken as a general rule. Whatcan be used as a general rule for future studies is the mechanism ofsite formation processes we identified in this study.

The processes of infill include wall disintegration and collapse.Walls in this study have collapsed both outwards and inwards. Thisobservation is in contrast to McIntosh’s (1974) observations,however, in this study we do not know the exact reason for the wallcollapse as no undercutting was observed, thus the possibility ofcollapse due to earthquakes and/or post-abandonment deliberatehuman destruction are also valid. Walls also disintegrate as singlebricks collapses, either inwards or outwards. Therefore, singlebricks and/or intact wall parts may be associated with houseabandonment. These features are then buried as sediments accu-mulate within the abandoned house but also around its walls onthe outside, slowly forming a minor mound.

Fig. 10 presents a schematic summary of the processes thatoperated in the formation of the microscopic features of the infillsediments at the site. Once buried, brick fragments undergo furtherdegradation by percolating water evident by the presence of silty-clay crusts on their edges and within voids (Fig. 9c). Anothermechanism of mud brick degradation is the direct impact of rainwater, washing the mud down the walls and into the spacesbetween the walls, forming vast silty-clay microlaminae that fillinternal house spaces from wall to wall (see archaeological impli-cations below). The various components in the bricks e the organicstraw temper, the coarse mineral fraction and the fine mineralfraction e undergo different formation pathways (Fig. 10). Whenthe surface of a brick degrades, the organic material (i.e., the vegetalmaterial such as the straw) is exposed and rapidly degrades. Duringa rain event, the fine and coarse mineral fractions of the brick will

Fig. 9. Microphotographs of representative infill sediments in thin section, all in plane polarized light. (a) Brown/gray infill sediment resulting frommud brick degradation. Note theabsence of planar voids after vegetal temper, void infillings and crust formations. (b) Bands of medium sand within finer grained wind blown sediments, possibly indicating gravityfall of quartz grains from walls following wind abrasion. (c) Initial stages of mud brick degradation around brick fragments within the infill sediments. Note the formation of silty-clay crusts around the edges of the mud brick fragment. (d) Microlaminae of graded bedding indicating cycles of rain and/or eolian events. Note that medium and coarse sand grainsare ’floating’ on silty-clay laminae indicative of gravity mud slurry flows during rain events. In addition, note the disruption of bedding due to bioturbation. (For interpretation of thereferences to color in this figure legend, the reader is referred to the web version of this article.)

D. Friesem et al. / Journal of Archaeological Science 38 (2011) 1135e1147 1145

move away from the wall, depending on the energy of water. If theenergy is high, both coarse and fineminerals will formmud slurriesthat slowlymove by gravity to form thinmicrolaminae of mud brickmaterial (Fig. 9b and d). With the decrease of water energy as therain event diminishes, only the fine fraction, composed mainly ofcalcitic-clay and silt grains, is moved away from the wall andaccumulates as a crust. In cases of slight puddling, graded beddingwill be formed, with the topmost bed composed of pure, oriented,clay. At this stage, the microstructure of the mud brick materialdoes not include straw fragments and will thus not include largeplanar voids (in contrast to un-degraded brick material).

Infilling processes in an arid environment such as in this studyalso include the deposition of wind blown sediments and theirmixing, to various degrees, with the degraded mud brick material(Fig. 10). This study shows that such mixing is quite extensive indi-cating that “mud-brick material” in arid environments is not expec-ted to resemble the original mud brick composition. Mineralogical,elemental and micromorphological analyses are thus essential toolsto evaluate and understand the extent ofmixing processes of varioussedimentary sources in archaeological sites. An interesting observa-tion is the presence of coarse sand grains togetherwith smallerwindblown grains, suggesting that the coarse sand is in fact introducedfrom the degrading walls, possibly as single-grains that detach fromwall surfaces possibly due towind abrasion. The last process to act onthe forming mound, occurring during and after depositionalepisodes, is bioturbation (Fig.10). As the studied site is abandoned foronly ca. 60 years, it is possible that in an archaeological site, wherebioturbation continued to act within the infill sediments formillennia, the infill sediments may be mixed to a degree that nolayering could be observed macroscopically. We would expect,though, that patches of intact layers will still be detected micro-morphologically and will help in identifying formation processes.

5.2. Infilling rate and its implications for the study of activity areas

In general, the abandoned house serves as a trap for both mudbrick material and for dust. The result is a shallow mound (anincipient tell). The total thickness including all sediment groups is70e80 cm (Fig. 5), spanning ca. 60 years that passed since the househad been abandoned. Clearly the rate of infilling was not constantas the study area is located within shifting sand dunes and expe-riences several sand storms annually. In addition, the area experi-ences major annual differences in precipitation, and deflationprocesses are also common. Thus the accumulation is not consis-tent over time, and microlaminae cannot be used as indicators forseasonal changes.

5.3. Archaeological implications for field archaeology

Some of the results of this study bear important implications forfuture archaeological excavations of mud brick structures in aridenvironments. The gray microlaminated infill surfaces that formeddirectly from mixing of mud brick material and wind blown sedi-ments may easily be mistaken as floors during an archaeologicalexcavation. An important observation is that these pseudo-floorsurfaces are intimately associated with walls e they are inclinedcloser to the walls and horizontal in the middle of the built area,forming a U-shaped macro-stratigraphy (Koulidou, 1998 has alsoobserved the same pattern). Such observations between walls andfloors at archaeological sites are abundant (e.g., Albert et al., 2008 onphytolith-rich layers and their relation towalls at Iron Age Tell Dor).This clearly complicates archaeological interpretation, however,with the use of micromorphology these pseudo-floors are readilyidentifiable as the result ofmud slurry deposition using criteria suchas the presence of graded bedding and clay crusts (Fig. 9b, c and d).

Fig. 10. A geoarchaeological model for the microscopic degradation processes of mud bricks and mud brick walls in an arid environment. Note that the coarse fraction, fine fractionand organic components simultaneously undergo different degradation pathways, resulting in the formation of banded sedimentary layers across the entire internal surface of theabandoned house.

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An important outcome of this study is the observations regardingplacement of various infill sediments in relation to walls. The sedi-mentation pattern (Fig. 5) indicates that the areas close to thenorthern and southernwalls have thicker accumulation of un-mixedmud brick material relative to the central part of the roofed area.Thewind blown sediments have quite a similar thickness across themeasured section. The gray mixed sediments are thicker in thecentral part of the section, indicating greater mixing in this context.Overall, this pattern indicates that most un-mixed mud brickmaterial is expected tobe foundclose todegradedmudbrickwalls inan archaeological context. Following this observation, we suggestthat the best localities within abandoned archaeological houses forfinding pristine microscopic activity remains should be close towalls, and the identification of the contact between the activity floorand degraded mud brick on it, will improve activity area interpre-tation. In addition, localities where massive wall collapse is identi-fied should too be considered preferential for microscopic activityremains research due to the fast burial at these localities.

When conducting activity area and household archaeologyresearch one needs to know the exact surface of floors in order toevaluate whether artifacts used for activity area reconstruction areplaced directly on the floor surface below mud brick wall degra-dation sediments, or are placed slightly above the floor surfacewithin mud brick degradation products. As often happens in tellarchaeology, the exact surface of floors is not easy to determine,especially when the same soil type had been used for flooring andwall construction. This study gives micromorphological criteria toapproach the distinction between floor and mud brick degrada-tion material in an arid environment and thus to better interpretarchaeological activity area reconstruction.

Lastly, this study shows that in contrast to various previousstudies that identified the sources of sediments for mud brickpreparation in alluvial deposits in the vicinity of the sites (e.g.,Davidson, 1973; Goldberg, 1979; Kemp, 2000; Nodarou et al., 2008;Rosen, 1986), here we showed that a local paleosol was used as the

raw material for brick preparation. We note that the elementalcomposition and micromorphological characteristics of the mudbricks are not identical to those of the Husmas paleosol, indicatingthat the paleosol was manipulated by the builders while the mudbricks have been prepared.

6. Conclusion

The study of human made mud bricks enables to understandsocial aspects related to buildings/houses, human selection andprocurement of soil raw material, architecture and the influence ofthese activities on the landscape (Goldberg, 1979; Goodman-Elgar,2008; Matthews et al., 1997; Rosen, 1986; Shahack-Gross et al.,2005; Stevanovic, 1997). A model of the degradation and infillprocesses in an abandoned mud brick house has been presented.This study was conducted in an arid environment where processesare greatly influenced byeolian deposition.Wedonotexpect similarprocesses to act in more humid environments, such as Mediterra-nean and temperate climates. The next phases in our study will aimat studying mud brick house degradation in humid environments,and also testing possibilities for enhancing identification of activityareas based on microscopic and chemical remains.

Acknowledgments

We are indebted to Dan Gazit without whom this project wouldnot have been carried out as smoothly and successfully as it did. Wewould also like to thank our colleagues, especially Aren Maeir forcontributing excavation equipment, Lior Regev for help with FTIRanalyses and Steve Weiner for commenting on an earlier draft ofthis manuscript. We are also grateful to those who helped in theexcavation: Noa Lavi, Efrat Bocher, Shira Gur-Arie, Dan Cabanes,Maite Cabanes and Tomer Aharon. The project was funded bya grant from the Israel Science Foundation (Bikura track, 527/09) toRSG and was assisted by funding from the Kuschitzky Fund at the

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Dept. of Land of Israel Studies and Archaeology (Bar Ilan Univer-sity), the Kimmel Center for Archaeological Science at the Weiz-mann Institute and a European Research Council under theEuropean Community’s Seventh Framework Programme (FP7/2007-2013)/ERC grant agreement no 229418 to Israel Finkelsteinand Steve Weiner.

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