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Journal of Archaeological Science 47 (2014) 22e38

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Journal of Archaeological Science

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Holocene environmental change in Eastern Spain reconstructedthrough the multiproxy study of a pedo-sedimentary sequence fromLes Alcusses (Valencia, Spain)

Rebeca Tallón-Armada a,*, Manuela Costa-Casais b,c, Judith Schellekens a,e,Teresa Taboada Rodríguez a, Jaime Vives-Ferrándiz Sánchez d, Carlos Ferrer García d,Daniel Abel Schaad e, José Antonio López-Sáez e, Yolanda Carrión Marco f,Antonio Martínez Cortizas a

aDepartamento de Edafoloxía e Química Agrícola, Facultade de Bioloxía, Universidade de Santiago de Compostela (USC), Rúa Lope Gómez de Marzoa, s/n,Campus Vida, 15782 Santiago de Compostela, A Coruña, Spainb Instituto de Ciencias del Patrimonio (Incipit), Consejo Superior de Investigaciones Científicas (CSIC), San Roque, 2, 15704 Santiago de Compostela,A Coruña, SpaincDepartamento de Xeografía, Facultade de Xeografía e Historia, Universidade de Santiago de Compostela (USC), Praza da Universidade, 1,15782 Santiago de Compostela, A Coruña, Spaind Servicio de Investigación Prehistórica, Museo de Prehistoria de Valencia, Diputación de Valencia, C/Corona 36, 46003 Valencia, SpaineGrupo de Investigación Arqueobiología, Centro de Ciencias Humanas y Sociales (CCHS), Consejo Superior de Investigaciones Científicas (CSIC), C/Albasanz,26-28, 28037 Madrid, SpainfUniversidad Nacional de Educación a Distancia (UNED), C/Casa de la Misericordia, 34, 46014 Valencia, Spain

a r t i c l e i n f o

Article history:Received 5 March 2013Received in revised form20 March 2014Accepted 24 March 2014Available online xxx

Keywords:PedoarchaeologyPalaeoenvironmental reconstructionGeochemistryPyrolysiseGC/MSMicro-charcoalPollenMediterranean Spain

* Corresponding author. Tel.: þ34 656 408 481.E-mail addresses: rebeca.tallom@gmail.com, rebe

schellekens.j@hetnet.nl (J. Schellekens), teresa.taboa(C. Ferrer García), dabel222@hotmail.com (D. Abel Scortizas@usc.es (A. Martínez Cortizas).

http://dx.doi.org/10.1016/j.jas.2014.03.0230305-4403/� 2014 Elsevier Ltd. All rights reserved.

a b s t r a c t

We present a multiproxy characterization of a complex, polycyclic soil sequence from Les Alcusses,Moixent (Valencia, SE Spain). The area has abundant settlements dating from early Neolithic to Romantimes. The sequence comprises six main units, dating back to 8.7e8.5 ka cal BP. We integrated miner-alogy, inorganic (pH, grain size, elemental composition) and organic chemistry (pyrolysis gas chroma-tography/mass spectrometry, pyrolysiseGC/MS), micro-charcoal, pollen and non-pollen palynomorph(NPP) data. All data is contextualized within a framework of archaeological information and radiocarbondating, with the aim of deciphering the Holocene environmental changes.

We infer a shift from wetter and warmer, in the early-mid Holocene, to drier and cooler climaticconditions with increased fire occurrence, in the mid-late Holocene (particularly after 5.3 ka cal BP).Although the pollen record indicates a rapid forest retreat and expansion of grasslands for the Neolithicperiod, local proxies (molecular soil OM indicators and NPP) point to the presence of pine forest in thestudied location well after the regional decline started. The same proxies suggest a sharp forest declineafter about 7.0 ka cal BP. Strong soil erosion, likely linked both to climatic instability and the intensifi-cation of human exploitation, resulted in a hiatus from the late Neolithic to the Roman period. A certainclimate amelioration, wetter conditions and land abandonment or, at least, lower human pressure, aresuggested for the late Roman period/Early Middle Ages. Direct evidence of changes in soil properties dueto agriculture was not detected in the sequence except for the upper soil unit studied, which reflectsintense agricultural management (with the possible use of agrochemicals).

� 2014 Elsevier Ltd. All rights reserved.

ca.tallon@usc.es (R. Tallón-Armada), manuela.costa-casais@incipit.csic.es, manuela.costa@usc.es (M. Costa-Casais),da@usc.es (T. Taboada Rodríguez), jaime.vivesferrandiz@dival.es (J. Vives-Ferrándiz Sánchez), carlos.ferrer@dival.eschaad), joseantonio.lopez@cchs.csic.es (J.A. López-Sáez), yolanda.Carrion@uv.es (Y. Carrión Marco), antonio.martinez.

R. Tallón-Armada et al. / Journal of Archaeological Science 47 (2014) 22e38 23

1. Introduction

Geoarcheology integrates several disciplines of the Earth Sci-ences, for example Geomorphology, Sedimentology, Pedology,Geochemistry, in the study of environmental archives in andaround archaeological sites. Their application provides informationto identify the role of human activity in landscape evolution insupport of more conventional archeology (Butzer, 1967, 1975, 1982;Davidson and Shackley, 1976; Goldberg et al., 2001; Benedetti et al.,2011). Pedoarchaeology is a branch of Geoarcheology that concernsthe study of soil in archaeological contexts (Walkington, 2010). It isthe focus of our study.

Investigations highlighting the importance of soils in archaeo-logical studies are on the increase. Present soil properties resultfrom the functioning of processes through time, so that their studypotentially unlocks a record and store of signals of environmentalchange and the role played by climate and human activities inlandscape transformations (Holliday, 2004; Entewistle et al., 2007;Benedetti et al., 2011; Walkington, 2010). Complex, polycyclic, soilsequences are three dimensional, process-response systems thatrepresent geoarchives that may be particularly valuable in thiscontext. Provided the complexities of pedogenetic and diageneticprocesses can be unraveled, both visible properties (e.g. sedimen-tary and morphological features) and more occult ones (e.g.geochemical signals) may be of help in reconstructing palae-olandscapes and palaeoenvironmental conditions (MartínezCortizas, 2000; Walkington, 2010). In addition, soils may storesuch palaeoecological and archaeological indicators as phytoliths,charcoal, pollen and human artifacts (Walkington, 2010). Incontrast to environmental archives located far from where humanactivities actually took place, soils have a much wider distributionand since they are the surface on which humans develop their ac-tivities e settlements, agriculture and other land uses etc. e iden-tifiable signals may have been left (Homberg et al., 2005).

In this paper we present a pedo-archaeological study of a soilsequence located in Mediterranean Spain. This region has under-gone intense environmental change (Berger and Guilaine, 2009;Jalut et al., 2009; Carrión et al., 2010: Roberts et al., 2011a) and ischaracterized by the presence of a large number of archaeologicalsites, some of them key to understanding the early Neolithiccolonization and the development of agriculture in Iberia (Zapataet al., 2004; Bernabeu and Martí, 2012). To unravel its Holoceneevolution both factors of change (climate variability and humanactivity) and their interaction through time have to be resolved.

There is a large body of literature about Holocene climate inMediterranean Iberia and its relationship to prehistoric evolution.Some studies show that the dynamic changes in the extension andintensity of land use may have produced significant effects in thelandscape, as in the soils and the vegetation cover of the mostecologically sensitive areas (Zapata et al., 2004). Most of these in-vestigations are based on the interpretation of sedimentological,archaeobotanical (pollen, charcoal, diatoms, etc.) (Jalut et al., 2009;Pérez Jordà et al., 2011; Peyron et al., 2011; Roberts et al., 2011a),mineralogical and geochemical (Martín-Puertas et al., 2008) in-dicators obtained from lake sediments. Other disciplines that pro-vided archaeological and palaeoenvironmental information includearchaeobotany (Mercuri et al., 2011), isotopic chemistry (Robertset al., 2011b), and sedimentology/geomorphology (Ferrer García,2005, 2011). Some of them also correlate Neolithic evolution withenvironmental change (Berger and Guilaine, 2009).

Here, our multidisciplinary, pedoarchaeological research seeksto integrate studies of mineralogy, geochemical properties, mo-lecular chemistry of soil organic matter (OM), micro-charcoal andpollen, and to contextualize the information with the broaderarcheological picture. The aim is to reveal the evolution of the study

area and to identify the factors involved, particular attention beingpaid to signals of human activity.

Our mineralogical-geochemical characterization provides datacrucial in identifying erosion/sedimentation and pedogeneticalprocesses. Pollen and micro-charcoal are studied to reconstructvegetation change and fire events possibly related to climate con-ditions and/or human activity (Carrión et al., 2010). PyrolysiseGC/MS is a powerful method to characterize soil OM (e.g. Almendroset al., 1998; Nierop et al., 2001) and provides information onvegetation and land-use characteristics (Tinoco et al., 2006;Buurman and Roscoe, 2011; Schellekens et al., 2013a,b), the de-gree of decomposition of the OM (e.g. Nierop et al., 2005; Yassir andBuurman, 2012) and fire history (González-Pérez et al., 2004; Kaalet al., 2009). With the support of radiocarbon dating, all data areinterpreted in terms of dominant environmental conditions(climate and human activity) and contextualized with availablereconstructions of Holocene environmental change in the WesternMediterranean.

To the best of our knowledge, the combination of proxiesstudied by us has not been applied before in an archaeologicalcontext.

2. Material and methods

2.1. Site description and soil sampling

The study area, Les Alcusses (Moixent, Valencia, Spain), has beenintensely occupied from the Neolithic to the Roman period (Fig. 1).It is a small hanging valley which lies at 550 m of altitude, confinedbetween Serra Grossa (750m a.s.l.) and the valley of the of Cànyolesriver (450m a.s.l.). The area is part of the northern reach of the BeticDomain into the inner part of Valencia, where tectonic movementsled to the formation of smooth, folded, structures with a NEeSWtrend.

Climatic conditions in the area are characterized as sub-humidto dry Mediterranean, with an average annual precipitation of600 l m�2, with marked seasonality, and average temperaturearound 14e15 �C (Pérez Cueva, 1994).

Structurally the region is a series of anticlinal mountain rangesseparated by synclinal valley corridors. Carbonate rocks crown theanticlines with Miocene marine marls in the valleys. The Pla de LesAlcusses, although part of an anticline, is a subsided block half waybetween these two structural features. A smooth relief with smallrounded hills, small depressions, and flat valley bottoms charac-terizes the landscape.

In general, the soils the study area are poorly developedcalcareous Regosols (IUSS Working Group WRB, 2007), with fea-tures conditioned by the parent material and the rapid minerali-zation of the organic matter. The diagnostic horizon is an A umbricor ochric epipedon (Rubio et al., 1995). In piedmont or glacis loca-tions, these soils are constantly rejuvenated by the contributions ofnew material from the slopes (colluvium). The main soil propertiesare: high water holding capacity; structural stability of 5% incultivated soils and 44% in forest soils; cation exchange capacitybetween 12 and 21 cmolc kg�1; organic matter content between1.4% in cultivated soils and 7.7% in forest soils; carbonate contentabove 50% (Rubio et al., 1995).

The natural vegetation occupies marginal and limestone reliefs.It is highly degraded and potential vegetation (forest of Quercusrotundifolia) barely exists because human pressure and fires havereduced their later stages of succession. Present vegetation isdominated by strata (Quercus coccifera, Pistacia lentiscus, Rhamuslycioides, etc.) or “matojar” (Ulex parviflorus or Genista scorpius, Ericamultiflora, Rosmarinus officinalis, etc.) formations, sometimesaccompanied by pine (Pinus halepensis). Les Alcusses is mainly

Fig. 1. Location of the studied sequence and settlements dated from Neolithic to Roman period.

R. Tallón-Armada et al. / Journal of Archaeological Science 47 (2014) 22e3824

occupied by cultivated soils in small plots, with alternating cerealcrops, vineyards and orchards, separated by margins of naturalvegetation.

The pedo-sedimentary sequence of Bosquet (BQT) was sampledin a small, buried thalweg in the slope of the hanging valley, only100m away from the local divide, choosing themost representative

place in terms of stratigraphical units. The sequence is surroundedby Neolithic, Iron Age and Roman settlements (Fig. 1).

The sequence was directly sampled on a soil cut, by takingcontinuous sections of 5 cm in thickness (32 samples; Fig. 2). Theuppermost unit of the sequence, the present cultivated soil, wasnot sampled. Soil descriptions were made for each sample,

Fig. 2. Synthetic description of the morphological properties of the BQT sequence.

R. Tallón-Armada et al. / Journal of Archaeological Science 47 (2014) 22e38 25

following the Guide for Soil Description (FAO, 2006), and includedtexture, structure, consistency, plasticity, sedimentary and pedo-logical features, as well as color (using the Munsell Soil ColorCharts, 1967).

The soil description enables to define six units and corre-sponding soil cycles (Fig. 2). Of the bottom unit of the sequence wewere able to obtain only two samples (because of restrictions fordigging of the owner of the land). As a general feature, the materialwhich forms the sequence is dominated by the fine earth fraction(<2 mm), and showed a strong reaction to HCl 10% e indicatinghigh content in carbonates. It had hard to very hard structure andwas composed of aggregates with precipitated secondary carbon-ates covering ped faces (Fig. 2). Prehistoric pottery sherds of thelocal late Iron Age (ca. 2.4e2.1 ka BP), were recovered in units IVand II (Fig. 2). The top of unit II can be attributed to a sub-presentsoil layer, fossilized by sediment intentionally added during mid-twentieth century farming.

2.2. Mineralogy and physico-chemical properties

Samples were air dried and sieved, separating the coarse frac-tion (>2 mm, gravel) and the fine earth (<2 mm). All analyticaldeterminations were done in finely milled (<100 mm) and ho-mogenized subsamples of the fine earth fraction of the soil, exceptfor soil reaction (pH). The later was measured in water and KClsuspensions (1:2.5) with a pH meter, following standard pro-cedures (Guitián and Carballas, 1976; Urrutia et al., 1989).

The grain size analysis was done without previous eliminationof carbonates, as suggested by Van Reeuwijk (2002). Fifteen gramsof sample were shaken in suspension in distilled water for 24 h.After that the suspensions were separated into three fractions bywet sieving: <2e0.2 mm (coarse sand); <0.2e0.05 mm (fine sand)and <0.05 mm (silt þ clay).

The mineralogy was determined by XRD using a Philips PW1710diffractometer (CuKa radiation and graphite monochromator).Quantification of the mineral phases was done using Match! 1.11esoftware. Selected samples were also analyzed in oriented prepa-rations, solvated in ethylene glycol and heated to 550 �C for theidentification of clay minerals.

Total carbon and nitrogen were determined using a LECO CNS-2000 elemental analyzer, and the concentrations of some major,minor and trace elements (Si, Al, Fe, Ti, Ca, K, Rb, Sr, Y, Zr, Nb, Mn,Cu, As, Pb, Cl, Br) were obtained using two XRF equipments, whichare described elsewhere (Cheburkin and Shotyk, 1996; Cheburkinet al., 1997; Weiss et al., 1998). The quantification limits are:0.4 g kg�1 (Si, K), 0.02 g kg�1 (Fe, Ti), 0.04 g kg�1 (Ca), 1 g kg�1 (Al),1 mg g�1 (Rb, Sr, Y, As, Br), 0.3 mg g�1 (Zr), 0.5 mg g�1 (Nb, Pb),28 mg g�1 (Mn), 9 mg g�1 (Cu), 200 mg g�1 (Cl). The equipments arehosted in the Elemental Analysis and XRD-XRF units of the RIAIDT(Network of Infrastructures to Support Research and TechnologicalDevelopment) of the University of Santiago de Compostela.

2.3. Pollen analysis

The samples of unit V, assigned to the Neolithic period on thebasis of radiocarbon dating, were analyzed for pollen. They weretreated following the chemical methodology proposed by Faegriand Iversen (1989), which comprises an initial attack with HCland subsequent washings with NaOH. The sediment was thenconcentrated in heavy liquid in order to obtain separates of pollenand non-pollen palynomorphs (Goeury and De Beaulieu, 1979), andfinally treated with HFl. Pollen concentration was estimated byadding a Lycopodium tablet to each sample (Stockmarr, 1971).Anthropogenic taxa such as those belonging to Compositae (LópezSáez et al., 2003) aswell as ferns, hydro-hygrophilous taxa and non-pollen palynomorphs, were excluded from the total pollen sum

Table 1Results of radiocarbon age dating of the BQT sequence.

Sample Beta code Conventionalradiocarbonage

2 Sigma calibratedage

Delta 13C

Unit VI(192.5 cm)

Beta-293664 7820 � 50 BP 8710e8520Cal BP

�24.9%

Unit V(142.5 cm)

Beta-293665 4670 � 50 BP 5580e5520and 5480e5300Cal BP

�25.0%

Unit IV(107. 5 cm)

Beta-293666 1710 � 40 BP 1710e1530Cal BP

�25.1%

Unit III(87.5 cm)

Beta-293667 1620 � BP 1600e1410Cal BP

�25.2%

R. Tallón-Armada et al. / Journal of Archaeological Science 47 (2014) 22e3826

(>200 pollen grains) in the pollen diagram, as they are consideredlocal or extra-local, so they tend to be overrepresented (Wright andPatten, 1963).

2.4. Anthracology

From the fine fraction, we set apart a constant volume 10 cm3 ofsediment per sample (measured with a Hirschmann EM-Techcolorvolumetric pipette). After a first inspection, we found that charcoalfragments larger than 1 mm were systematically absent. The sedi-ment was washed on a 250 mmmesh, with a low-pressure shower-head in order to avoid charcoal fragmentation. The clean sedimentwas dried for several days onwhite blotting paper, the same type ofpaper that was used for subsequent manipulation and observationof sediment through the binocular, with magnification between30� and 60�. The use of the stereo microscope rather than othermethods (such as a polarized light microscope) allows discrimi-nating the fragments of carbonized xylem, from other sharp anddark-colored items, such as small fragments of fresh root bark,specially common in some samples. In case of any doubt, the cap-ture of the field of view on a completely focused image through thesoftware Helicon Focus allowed a detailed observation of thesamples and the final discrimination of the charcoal particles.

2.5. Molecular composition of soil OM (pyrolysiseGC/MS)

Before OM extraction, carbonates were removed by adding20 ml hydrochloric acid (5 M, 20 ml) to 5 g of each soil sample. Theresidue was extracted with NaOH (0.5 M, 20 ml), shaken for 24 hunder N2 and centrifuged (1 h) at 4000 g. The extract was decantedand the extraction repeated a second time. The extracts werecombined, acidified to pH 1 with hydrofluoric acid-hydrochloricacid (3:1), shaken overnight, dialyzed against distilled water (cutoff 10,000 D), freeze-dried (e.g. Nierop et al., 2001) and analyzedwith pyrolysiseGC/MS.

PyrolysiseGC/MS was performed with a Pt filament Pyroprobe5000 (Chemical Data Systems, Oxford, USA) coupled to a 6890N GCand 5975B MSD GC/MS system from Agilent Technologies (PaloAlto, USA). Samples were embedded in glass wool-containing fire-polished quartz tubes. The GC/MS transfer line was held at 270 �C,the ion source (electron impact mode, 70 eV) at 230 �C and thequadruple detector at 150 �C. The GC was equipped with a (non-polar) HP-5 MS 5% phenyl, 95% dimethylpolysiloxane column(length 30 m; internal diameter 0.25 mm; film thickness 0.25 mm).Helium was used as the carrier gas (constant gas flow, 1 ml/min).Pyrolysis products were identified using the NIST ’05 library.

All prominent pyrolysis products were quantified, resulting in atotal of 80 products (SI_Table 2). They were grouped, according toprobable origin and chemical similarity, into a number of sourcegroups: aliphatic biopolymers (including n-alkanes, n-alkenes,methylketones, fatty acids, methylesters, propylesters), N-com-pounds, phenols, lignin moieties, aromatics, polyaromatics andpolysaccharides. Quantifications were based on the peak area ofcharacteristic ions (m/z values) of each pyrolysis product. Allquantifications were checked manually. For each sample, the sumof the quantified peak areas was set at 100% and relative amountswere calculated with respect to this sum. The resulting quantifi-cation allows comparison of the abundance of each product withina set of samples.

2.6. Radiocarbon age dating

The silt þ clay fraction of selected samples was sent for AMSradiocarbon age dating to Beta Analytic Inc (Miami, USA). Calibra-tionwas done using the Intcal04 calibration curve and the program

Calib 2.0 (Stuiver and Reimer, 1993). Ages are expressed as cali-brated years before present at 2 s (Table 1).

Dating of soil organic matter of buried epipedons may not pro-vide reliable ages due to carbon recycling, incorporation of juvenileorganic matter (via roots, for example), bioturbation, etc. (Wanget al., 1996; Kristiansen et al., 2003), making the chronologicalinterpretation of pedo-sequences highly uncertain. But, as sug-gested by different researchers (Tonneijck et al., 2006; Leopold andVölkel, 2007; Kaal et al., 2008), under certain circumstances it mayrender useful ages. We assume this is the case for the BQT sequencebecause: i) the OM (Section 3.3) of buried epipedons is composed ofstrongly degraded material, ii) in carbonate-rich soils the OM formshighly stable organo-mineral complexes with none or negligibleverticalmobility, iii) the strong soil structure limits root penetration,iv) we did not find evidence of significant bioturbation, and v) thedates obtained increase with depth and provide a chronologicalframework for the reconstructed environmental conditionswhich isconsistent with that proposed for the region using different andmore reliable archives (as lake sediments).

2.7. Statistical analysis

Factor analysis by principal components, in correlation mode,was applied to the physico-chemical properties (pH and fine sandcontent) and elemental composition, to synthesize the chemicalcomposition of the soil samples, and to investigate the main factorscontrolling it. The analysis was done with standardized data toavoid scaling effects and provide average centering.

Although the potential advantages for exploring large data setsand obtaining synthetic, process-based, interpretations, multivar-iate statistics are not frequently used in pedogenetic studies(Mellor, 1987; Meijer and Buurman, 1997; Thanachit et al., 2006;Martínez Cortizas et al., 2007; Dreibrodt et al., 2013). As stated inthe introduction, we assume that present soil properties are theresult of processes e pedogenetic and diagenetic (in the case ofburied soils)e that have operated through time under a given set ofenvironmental conditions, and are thus potential proxies for thereconstruction of past environments. The co-variation of severalsoil properties (expressed as a principal component) points to acommon underlying factor/process that we should be able tointerpret. The record of the factor scores of that component in apedo-sequence can thus be taken as a measure of the relative in-tensity of the underlying process.

3. Results

3.1. Physico-chemical properties and elemental composition

The most abundant fraction in the BQT sequence is the sil þ clay(56.3 � 6.5%), followed by fine sand (39.3 � 5.8%) and coarse sand(4.4 � 1.3%) (Table 2 and SI_Fig. 1). The dominant minerals are

Table 2Average (%), standard deviation (�) and range (minimumemaximum) of the grainsize fractions (cS: coarse sand; fS: fine sand; S þ C: silt þ clay) analyzed in the BQTpedo-sedimentary sequence (n: number of samples of each unit).

Unit n cS fS S þ C

II 7 3.0 � 0.4 (2.4e3.4) 35.6 � 4.3 (32.0e42.2) 61.4 � 4.5 (54.6e64.8)III 5 3.8 � 0.9 (2.6e4.6) 37.6 � 3.7 (34.1e43.4) 58.7 � 4.5 (52.0e63.3)IV 6 5.0 � 0.5 (4.4e5.7) 43.9 � 2.6 (37.6e46.2) 51.1 � 2.8 (48.2e56.4)V 11 5.1 � 1.4 (2.9e7.2) 42.4 � 2.9 (37.6e46.2) 52.7 � 3.8 (48.8e58.4)VI 2 4.4 � 1.4 (2.4e3.4) 37.4 � 0.3 (37.2e37.7) 58.2 � 1.0 (57.4e58.9)

Fig. 3. Vertical distribution of the fine sand content (%), most abundant minerals (%) (C: calcite; Q: quartz; Clay Min: clay minerals; feldspars), soil reaction (pHw, pH in water; pHk,pH in KCl), total C and N (in g kg�1).

R. Tallón-Armada et al. / Journal of Archaeological Science 47 (2014) 22e38 27

calcite, quartz and clay minerals (smectite, mica and/or kaoliniteminerals) (Fig. 3). Calcite contents are higher in samples of unit II(66 � 5%), III and IV (61 � 4%) than in unit V (54 � 5%). Quartzcontent varies between 18 and 38% (27 � 5%); the lowest valueswere found in unit VI (18%) and the highest in unit V (32 � 5%).Clay minerals follow an opposite pattern to calcite, showingsmectites in larger amounts in samples of unit V (14e27%) andmicas in the other units analyzed. Dolomite and feldspars werefound in traces in some samples, mostly of units II and IV (feldspars)and III (dolomite) (Fig. 3).

Soil reaction was alkaline in all samples, typical of carbonatematerials, with values inwater suspensions (pHw) between 8.3 and

Fig. 4. Vertical distribution of the concentrations of some se

8.9 and 1.0e1.5 units lower in KCl (pHk) (Fig. 3). The lowest pHvalues were found in units VI and V (below a depth of 135 cm), asharp increase occurs at the base of unit IV, and values of pHwremain above 8.6 to the top of the sequence.

Nitrogen contents are low (0.4e1.2 g kg�1) and show an irreg-ular depth record (Fig. 3). Carbon does not follow the same pattern,showing a maximum content in the most superficial sample(77 g kg�1) of unit II, decreasing values (59 g kg�1) to a depth of170e175 cm and an almost steady increase from there to the base ofthe sequence.

Most of the other major and minor elements analyzed (Si, Al, Fe,Ti, and K) show quite similar depth profiles (Fig. 4 and SI_Fig. 2).Low concentrations (150e170 g kg�1, 24e36 g kg�1, 13e15 g kg�1,1.1e1.4 g kg�1, 10e14 g kg�1, respectively) were found until 135 cm(units II, III and IV), the highest values (193 g kg�1, 56 g kg�1,175 g kg�1, 1.7 g kg�1, 16.5 g kg�1 respectively) between 135 and175 cm (unit V), and decreasing contents to the base of thesequence (Fig. 4 and SI_Fig. 2). Silicon and Al have a local minimumat 165e170 cm (Fig. 4). Calcium shows an opposite distribution tothat of these elements (r �0.76 to �0.93), but highly similar to thatof C (r 0.95) (Fig. 4). Calcium and C concentrations are significantlycorrelated (r 0.81) with carbonate content (calcite þ dolomite) and

lected major (in g kg�1) and trace elements (in mg g�1).

Table 3Factor loadings of the physico-chemical properties and elements used in the PCA.Eigv: eigenvalue, Var: percentage of variance, Acc: cumulative percentage of vari-ance explained.

Cp1 Cp2 Cp3 Cp4

Fe 0.92 0.16 �0.15 �0.08Zn 0.91 �0.05 0.14 �0.12Ti 0.88 0.34 �0.23 0.01Rb 0.85 0.39 �0.24 �0.04Br 0.83 0.25 �0.28 �0.28Y 0.83 0.21 �0.19 �0.16Al 0.82 0.17 �0.13 0.16Mn 0.79 0.13 0.06 0.26Si 0.74 0.43 �0.25 0.25K 0.74 0.46 �0.17 �0.01N 0.66 0.40 0.18 0.34pHw �0.65 0.01 �0.02 0.49Sr �0.66 �0.63 0.31 0.00C �0.68 �0.58 0.41 �0.04Ca �0.81 �0.41 0.34 �0.04pHk �0.85 0.01 0.08 �0.01fS 0.29 0.88 �0.17 0.14Zr 0.04 0.84 �0.07 �0.17As �0.02 0.04 0.90 �0.31Cl �0.19 �0.31 0.71 �0.32Cu �0.21 �0.31 0.76 0.35Pb 0.03 �0.04 �0.25 0.86Eigv 10.2 3.6 2.8 1.7Var 46.4 16.3 12.6 7.9Acc 46.4 62.7 75.3 83.2

R. Tallón-Armada et al. / Journal of Archaeological Science 47 (2014) 22e3828

Si (r 0.85) with the sum of silicate minerals (quartz þ clayminerals þ K-feldspars).

Of the trace elements, Rb (40e64 mg g�1), Y (10e18 mg g�1), Mn(200e300 mg g�1), Zn (24e44 mg g�1) and Br (2e23 mg g�1) followthe same distribution pattern of most of the major/minor elements(r 0.60e0.95), while that of Sr (517e524 mg g�1) is similar to Ca (r0.93) (Fig. 4 and SI_Fig. 2). Zirconium concentrations (86e249 mg g�1) are largely variable, Cu (8e35 mg g�1), As (<1e9 mg g�1)and Cl (70e900 mg g�1) show elevated concentrations in the upperunit (II), while Pb has a quite irregular depth profile (Fig. 4).

To synthesize the main chemical signature of the physico-chemical properties and elemental composition of the BQT pedo-sedimentary sequence we performed a principal componentsanalysis. Four components accounted for almost 84% of the totalvariance (Table 3). The first component, Cp1, explains 46% of thevariance and shows large to moderate positive loadings (0.92e0.66) of Fe, Zn, Ti, Rb, Br, Y, Al, Mn, Si, K, and N, and large to mod-erate negative loadings (�0.85 to �0.65) of pH in KCl (pHk), Ca,total C, Sr and pH inwater (pHw) (Table 3). The second component,Cp2, explains 16% of the variance and is associated to large loadings(0.88, 0.84) of fine sand and Zr. The third component, Cp3, explains13% of the variance showing As, Cl and Cu large positive loadings(0.90e0.71; Table 3). While the fourth component, Cp4, explains 8%of the variance and Pb is the only element with a large factorloading e and will not be further discussed.

3.2. Pollen, non-pollen palynomorphs (NPP) and micro-charcoal

A synthetic pollen diagram for the samples analyzed is given inFig. 5, and SI_Table 1 provides a reference of main pollen and NPPindicators and their interpretation. The bottom of unit V (185e190 cm, Fig. 5) shows the highest values of arboreal pollen (70%) ofthe whole unit. Pinus pinea type (50%) and riparian woods (15%)with Fraxinus and Salix are the main taxa, while Quercus, Ulex typeand taxa which are components of the thermophilous shrublandshow very low values. Percentage of herbaceous plants is conse-quently low. Ferns and NPP also have low percentages, although

coprophilous fungi, Coniochaeta cf. ligniaria (HdV 172) and espe-cially Glomus (HdV 207) display noticeable values.

Along unit V significant changes in the pollen record are re-flected (Fig. 5). The percentage of P. pinea type fall, accompanied bya slight increase of evergreen Quercus, Ulex type and the compo-nents of the thermophilous shrubland, coinciding with a sharp risein coprophilous fungal spores, and a slighter one of Chaetomium(HdV 7A). There is also a parallel decline of riparianwoodlands (5%).Arboreal pollen reaches its minimum values (20%) at 160e165 cm,while maxima in Poaceae and Fabaceae are found. Cichorioideaealso shows a large increase, while the first appearance of Medicagosativa and Vicia faba occur. Coprophilous fungi maintain their levels,while Chaetomium, Byssothecium circinans (HdV 16C), Coniochaetaligniaria and Glomus undergo significant increases. The abrupt in-crease of Pleospora sp. (HdV 3B) (Fig. 5) is also remarkable. Arborealpollen only slightly recovers at the top of the unit. V. faba reaches itsmaximum values while M. sativa appears sporadically. Both Plan-tago major/media type and Rumex acetosa type show very lowpercentages along the unit. No pollen grains of Cerealia have beenfound.

Micro-charcoal content in the BQT sequence (Fig. 6) is quite lowbelow 135 cm (units VI and V) and much larger in the upper threeunits, particularly in units IV and II. Some authors consider thatsmall charcoal particles produced in a fire are quickly scattered bywater or/and wind. Blackford (2000) established that only verysmall particles (<125 mm) are subject to rapid wind transport, andmost authors agree that, regardless of transport, there is always animportant accumulation of charcoal at the fire edge (Whitlock andMillspaugh, 1996; Gardner and Whitlock, 2001; Lynch et al., 2004;Colombaroli et al., 2008) and that particles larger than 125 mm aregenerally deposited within or very close to the fire perimeter. Ac-cording to these criteria, we have selected particles larger than250 mm e as indicated in the methods section e and consider theycan be used as a proxy for local fire events.

In most of micro-charcoal analyses, botanical identification isnot possible due to the small particle size. In this case, we tried toapproach the taxonomical content of the charcoal samples, but onlythose with a high charcoal content could be manipulated for SEMobservation. It was not possible to identify any fragment at speciesor genus level, because of the small size of the charcoal. However,microscopic identification revealed the presence of conifers (pineand juniper) and several species of angiosperms. Some of theanatomical features are the bordered pits (Fig. 7a) and uniseriateradius (Fig. 7e) of conifers. As for angiosperms, multiseriate andheterogenous rays (Fig. 7d and h) and spiral thickenings (Fig. 7f andg) were observed. In some fragments, the presence of such spiralthickenings in small vessels and fibers and their absence in largevessels points to the possibility that they belong to a species ofAnacardiaceae (the family of the lentisc) (Schweingruber, 1990:195). This feature has been frequently observed throughout thesequence, but no quantitative approach could be made. Cf. Vitis sp.has also been identified at 40e45 cm on the basis of the presence ofslit-like scalariform intervascular pits (Fig. 7c) andmultiseriate rays(Schweingruber, 1990: 734e735).

3.3. Selection of molecular proxies (pyrolysiseGC/MS)

The molecular composition of soil OM (Table 4a) indicates a lowcontribution of plant-derived OM and a high contribution ofmicrobial-derived and burnt material. The most abundant plantpolymers are cellulose and lignin. Lignin-derived pyrolysis prod-ucts show a relatively low contribution (except in the upper part ofthe sequence) and the abundance of the dominant pyrolysisproduct of cellulose (levoglucosan; Pouwels et al., 1987) wasnegligible and not quantified. A high contribution of microbial-

Fig. 5. Synthetic pollen diagram of the unit V (see Fig. 2) of BQT sequence. Riparian woodland: Fraxinus, Populus, Salix; thermophilous shrubland: Erica arborea type, Phillyrea, Pistacia terebinthus, Viburnum; coprophilous fungi:Gelasinospora (HdV 1), Sordariacea (HdV 55), Sporormiella (HdV 113), Podospora (HdV 368).

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Fig. 6. Micro-charcoal (number of fragments per 10 cm3 of soil) record and molecular composition of the soil organic matter of the BQT sequence (Microbial-derived OM, Charred-OM, Lignin (sum of lignins) expressed in %TIC). The gray line in the third panel represents the lignin content detrended from the depth/age assuming an exponential decrease inabundance. S/G ratio: syringyl/guaiacyl ratio; PA: polyaromatic hydrocarbon.

Fig. 7. Photographs of different micro-charcoal fragments found in the BQT sequence.

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Table 4a) Average, standard deviation of the abundances (in %) of the main groups of py-rolysis products of the extractable SOM of the BQT pedo-sedimentary sequence, andb) the molecular parameters and their interpretation.

a) Group Average % TIC S.D.

N-compounds 41.9 9.47Phenols 17.5 9.12Polysaccharides 14.7 8.14Aromatics 13.9 7.72Lignin 6.4 3.34Aliphatics 4.1 3.27Polyaromatic hydrocarbons 1.1 0.82

b) Molecular parameter Interpretation

Sum of Ps1, Ps3, N1, N7, N13 Microbial-derived OMSum lignin moieties (Lg1eLg13) Plant-derived OMSum polyaromatic hydrocarbons (PA1ePA8) Charred OM3-ring/2-ring PA ([PA6ePA8]/[PA1ePA5]) GymnospermsSyringyl/guaiacyl ([Lg8eLg13]/[Lg2eLg7]) Gymnosperms

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derived OM is indicated by the high abundance of N-compounds incombination with the dominant contribution of low-molecularweight pyrolysis products to the polysaccharide group (Buurmanand Roscoe, 2011). Furthermore, the high abundance of poly-aromatic pyrolysis products (Table 4) and benzonitrile (SI_Table 2)point toward a considerable contribution of burnt material(González-Pérez et al., 2004; Kaal et al., 2009). Thus, the abundanceof microbial-derived carbohydrates and N-compounds, and ligninpyrolysis products is used to indicate microbial and plant OM,respectively, while the abundance of polyaromatic pyrolysis prod-ucts can be used to reflect the contribution of fire residues.

In order to identify the botanical source of soil OM, ratios of py-rolysis productswere selected. Lignin solelyoriginates fromvascularplants. The ligninmacromolecule is composed of different moieties,including p-hydroxyphenyl, guaiacyl and syringyl moieties. Therelative abundance of these moieties highly differs between plantfamilies, and the syringyl-to-guaiacyl (S/G) ratio can be used todifferentiate between gymnosperm and angiosperm vegetation(Hedges and Mann, 1979). Because the general composition of soilOM indicates strong decay and a considerable contribution ofburning, plant characteristics according to lignin composition may

Fig. 8. Records of factors scores of the first three extracted principal components of the pvariations were obtained after subtracting the trend of total C content from the effect of th

have been lost due to selective decay of lignin moieties. The depthrecord of the phenanthrene-to-naphthalene ratio (3-ring PA/2-ringPA, Table 4b) appeared to coincide with that of pine pollen (Figs. 5and 6). Because phenanthrenes were found associated with pineforests while naphthalenes were associated with grasslands in soilslocated in the same area (Schellekens et al., 2013a,b), this ratio isproposed as a proxy for pine forest; it must bementioned, however,that this ratio may not function as such in different systems as theabundance of the polyaromatic pyrolysis products can be influencedby multiple factors. The selected molecular parameters and theirinterpretation are listed in Table 4b.

4. Discussion

4.1. Physico-chemical properties and elemental composition

Of the four components extracted with PCA, Cp1 describes thecontrasting distribution between elements related to the content ofcarbonates (Ca, C, Sr) versus those of other minerals (Fe, Zn, Ti, Rb,Y, Al, Mn, Si, K) and bulk soil OM content e the latter indicated bythe high positive loadings of N and Br (Br in soils is mostly presentas organo-halogenated compounds; Biester et al., 2006). Positivescores of Cp1 indicate low carbonate content and enrichment inother minerals and soil OM, whereas negative scores indicate highcarbonate content and lower contents in other minerals and soilOM. The depth record of Cp1 factor scores (Fig. 8) shows positivevalues in the lower two units (VI and V), a large shift to negativevalues at the base of unit IV and relatively constant valuesthroughout unit IV and the overlying units (III and II). The largestpositive scores occur in the upper part of unit V (135e165 cm), anddecrease with increasing depth into unit VI. This reflects carbonatedissolution, which is consistent with the lower soil reaction (i.e.lower pHw and pHk values), lower Ca, total C and Sr concentrationsand accumulation/neoformation of other soil components (clayminerals as smectites) in this soil cycle. Since the main pedogeneticprocesses in carbonate soils is the dissolution-precipitation ofcarbonates, accompanied by residual accumulation/neoformationof other minerals and stabilization/accumulation of organic matter,we interpret Cp1 as reflecting the intensity of pedogenesis in theBQT sequence: unit V having the largest intensity, followed by units

hysico-chemical properties and elemental composition of the BQT sequence. Soil OMe carbonates content (see the text).

R. Tallón-Armada et al. / Journal of Archaeological Science 47 (2014) 22e3832

VI and III, and units II and IV showing the lowest degree ofpedogenesis.

The second component accounts for the increase in grain sizeand Zr concentration. Zirconium is almost exclusively hosted byzircon, a dense mineral that is highly resistant to weathering andtends to concentrate in the fine sand and coarse silt fractions ofweathering products (Stiles et al., 2003; Taboada et al., 2006). Therecord of Cp2 scores (Fig. 8) shows close to zero values in units VIand V, the highest positive values in unit IV, decreasing values inunit III and most of unit II, and again increasing values in the uppertwo samples of unit II. Minor proportions (12e22%; square of thefactor loadings) of the variance of Si, Ti, K and Rb are also allocatedto this component (Table 3), suggesting a relative increase in someother resistant silicates (K-feldspars and/or micas) in the sandfraction. Coarsening of grain size and mineralogical fractionation inthe pedo-sequence may be related to increased erosion in the up-per slope and higher intensity of transport (allowing larger anddenser minerals to be moved). Thus, unit IV points to a reactivationof geomorphic processes, while units III and II indicate a decrease inerosion/transport intensity (higher silt þ clay content and lowersand content; SI_Fig. 1).

Cp3 factor scores (Fig. 8) reflect an increase in the concentra-tions of As, Cu and Cl in the upper samples of unit II. These elementsare not geochemically related, apart from the affinity of Cu and As(in some environments) for binding with the OM (Senesi et al.,1986; Bauer and Blodau, 2006). If the latter were the case, weshould expect them to be associated to Cp1, which is not shown inour data. But these elements can be incorporated in the soil by theaddition of fertilizers and biocides (as metallic and organo-chlorinated compounds). Since these upper samples of unit IIhave a recent origin we interpret this component as reflecting re-sidual contents of agrochemicals due to intense modern agricul-tural use.

The loading of C in Cp1 (Table 3) indicates that almost half (47%)of the variance of this element is accounted for by the content incarbonates. It also means that a large proportion of the variation(another half) should be related to a different source. One way todetermine the distribution of the variation not accounted for by aprincipal component is to detrend the element record from theeffect of the component by calculating statistical residues. Thelatter are the difference between the observed values and the ex-pected values calculated by linear regression between the scores ofthe principal component and the element concentrations. The re-cord of carbon residuals is shown in Fig. 8 (soil OM). Relativelyhigher values are found in the upper samples of each unit, as onemay expect if they represent the stable surface of buried soil cycles(i.e soil epipedons). We believe that this fraction does in fact reflectthe variation of organic carbon and thus interpret it as showing thevariations in the content of soil OM in the BQT sequence. This is alsosupported by the data on the molecular composition of soil OM, asit is discussed below. Unit V is the one preserving a deeper epi-pedon (35 cm deep), compared to the other units (15e20 cm inunits II and III, and 10 cm in unit IV). The thickness of the epipedonof cycle VI cannot be evaluated because we were only able tosample 10 cm. Nevertheless, we cannot rule out the possibility thatthe epipedons were, at least partially, truncated during the erosion/sedimentation events related to the build-up of the overlying units.

4.2. The molecular composition of soil OM

Depth records of the selected molecular proxies are shown inFig. 6. Microbial-derived OM dominates (abundances > 60%) inunits VI and V. A large decrease in abundance is shown in units IV toII, accompanied by a sharp increase in pyrolysis-products indicativeof burnt material (molecular fire markers). The abundance of

molecular fire markers is paralleled by the micro-charcoal recordand indicates increased fire incidence in the upper three units ofthe BQT sequence. Only the surface soil (unit II) lacks any goodagreement between fire-related pyrolysis products and micro-charcoal. This discrepancy between both methods can beexplained by the fact that decomposition is not yet advanced in thesoil of unit II; this means that only larger charcoal fragments arepresent, which are not extractable with NaOH and thus not presentin the pyrolysates. This interpretation suggests that the abundanceof micro-charcoal from upper soil layers should not be over-interpreted in comparison with that in paleosols, as stronglydecomposed charcoal fragments are not detectable with micro-charcoal analysis.

The lignin pyrolysis products show an exponential decreasefrom the upper samples of unit II to unit VI (Fig. 6), which corre-sponds to their relatively rapid degradation in soils (e.g. Thevenotet al., 2010). This pattern is interrupted by slight increases in theupper samples of each unit, coinciding with higher estimatedcontents of OM (Fig. 8), and also slight relative increases inmicrobial-derived OM (higher microbial activity) supporting thatthese sections reflect the remains of the epipedons of each soil unitof the sequence.

4.3. Soil processes, environmental conditions and chronology

Table 5 is a synthesis of the properties, related processes andenvironmental conditions reflected by each unit of the BQTsequence. The formation of the different soil-cycles of the BQTsequence is related to the alternation between, probably shortperiods of soil erosion and accumulation (increasing since5.3 ka BP) and longer periods of stability and pedogenesis emainlyin Neolithic times, related to the climatic conditions of the Holo-cene Thermal Optimum (HTM). They are discussed below in chro-nological order.

4.3.1. Unit VI (>8.7e8.5 ka cal BP)The properties of the two samples analyzed in this unit suggest

the presence of a moderately evolved, buried soil epipedon, char-acterized by relatively large contents of microbial-derived soil OM,a relative enrichment in plant-derived material (i.e. lignin), andminimum micro-charcoal content. We infer that this soil reflectsmild and, possibly, wet climatic conditions, with a low incidence oflocal fires.

Although a dry phase (10.9e9.7 ka cal BP) has been described forthe early Holocene in the Mediterranean (Lamb et al., 1995), thisseems not to be represented in the section of unit VI we analyzed.The climate it reflects agrees better with the wet conditionsattributed by Peyron et al. (2011). The later authors also highlightedthe importance of seasonality, with a Mediterranean-like climatealready present between 9.5 and 7.8 ka cal BP. This may correlatewith a lower carbonate leaching and re-precipitation of carbonatesshown by the upper part of unit VI; althoughwe cannot rule out theeffect of a post-depositional remobilization of carbonates from unitV and eventual precipitation in the upper part of unit VI. Regardingfire incidence, Gil-Romera et al. (2010) indicate that for most of theearly to mid-Holocene there was an uneven distribution of fires inSoutheastern Iberia, showing high altitude forests (broadleavedand coniferous) a highly dynamic post-fire response.

4.3.2. Unit V (<8.7e8.5 to 5.6e5.3 ka cal BP)Given the chronological framework for this unit (<8.5e

5.3 ka cal BP), the start of its formation was likely connected to theclimatic instability of the 8.2 ka event (Alley and Agustsdottir, 2005;Alley et al., 1997; Bond et al., 2001; Mayewski et al., 2004), forwhich arid to hyper-arid conditions have been reconstructed from

Table 5Chronology, synthesis of the geochemical signals (physico-chemical and OM composition) and inferred soil processes and environmental conditions of the BQT sequence.

Unit Depth(cm)

Radiocarbon age Physico-chemical signature OM and charcoal signature SOIL processes andenvironmental conditions

VI >190 8710e8500 cal BP(192.5 cm) Beta-293664

Low to moderate degree of leaching,predominance of fine grain size,high OM content.

High abundance of microbial OM,low content of fire markers, low lignincontent, low micro-charcoal content

Low to moderate degreeof pedogenesis, high OMdecomposition, fertile soil,low fire incidence. Mildand probably wet climaticconditions

V 190e135 5580e5300 cal BP(142.5 cm) Beta-293665

Highest degree of carbonate leaching,abundance of fine grain size,moderate OM content (higher inthe surface of the unit).

Dominance of microbial derived OM,low content or fire markers, low lignincontent, low micro-charcoal content

The largest degree ofpedogeneis, highlydecomposed OM, veryfertile soil, low fireincidence. Warm and wetclimatic conditions

IV 135e105 1710e1530 cal BP(107.5 cm) Beta-293666

Almost no evidence of carbonateleaching (highest carbonate content),grain size coarsening (increased sizecontent), low to very low OM content.

Decrease of microbial derived OM(slightly higher in the surface samples),abrupt increase in burnt material andmicro-charcoal, low to moderate lignincontent

Moderate degree ofpedogenesis, increasedsoil erosion, low degreeof OM decomposition,high incidence of fires.Arid conditions andprobably a change toincreased seasonalityand torrentiality

III 105e80 1600e1410 cal BP(87.5 cm) Beta-293667

Moderate degree of leaching, increase infine grain sizes, moderate to highOM content.

Low abundance of microbial derivedOM (slightly higher in the upper samplesof the unit), large abundance in fire markersand micro-charcoal (decrease in content atthe surface of the unit), moderate lignincontent

Moderate degree ofpedogenesis, decrease inthe intensity of soilerosion, the lowestdegree of OMdecomposition, lowerincidence of fires. Wetterconditions and decreasein torrentiality

II 80e45 Low degree of leaching, predominanceof fine grain size, with an increase in coarsefractions in the upper samples, evidenceof use of agrochemicals, high OMcontent

Low to moderate microbial derivedOM content, highest abundance of firemarkers and micro-charcoal, largestlignin content

Low degree ofpedogeneis, slight increasein OM decomposition,very high fire incidence,evidence of intenseagriculture use inrecent times

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several palaeorecords in Eastern Spain (López-Sáez et al., 2008;Carrión, 2003, 2002; Jalut et al., 2000, 1997). Berger and Guilaine(2009) proposed a transition between the hyper-aridity recordedfrom southern Spain to the southern Levant, and the central Eu-ropean zone affected by increasing humidity and cooling in theNorth Atlantic. This zone showed drought episodes alternatingwith heavy rainfall, leading to short and intense erosion/sedi-mentation events. The discontinuity may also correlate with thearid phase (8.4e7.6 ka cal BP) recorded in Morocco (Lamb et al.,1995) and the cooling recorded in Lago di Mezzano and manyother regional archives between 8.2 and 7.8 ka cal BP (Ramrathet al., 2000). In the BQT sequence, the low pollen concentrationand dominance of pine in the bottommost sample of unit V (Fig. 9)also suggest somewhat adverse climatic conditions shortly after the8.2 ka event.

Unit V contains the most evolved soil cycle of the sequence,showing intense carbonate leaching and clay minerals enrichment,a well-expressed horizonation and large contents of microbial-derived OM. The high degree of pedogenesis points to warm andwet climatic conditions, which are consistent with the HTM(COHMAP, 1998; Petit-Marie et al., 2000). Many terrestrial recordsacross the Mediterranean preserve evidence of the higher tem-peratures of the HTM (Cuenca Paya andWalker, 1986; Peyron et al.,2012); while humid conditions (Miller et al., 2009) and soil for-mation in inland areas of Valencia province (Ferrer García, 2011)have been identified after the 8.2 ka event and until 5.5 ka cal BP.

Despite the climate optimum, the pollen and NPP records reflectintense vegetation changes along unit V (Fig. 9). The vegetation ofthe initial phases of the sequence was dominated by pine forests, as

also found in other investigations in the area (Dupré, 1988; Carriónand van Geel, 1999). P. halepensis was most probably the dominanttree species, judging by the fact that P. pinea, which is also includedin the same pollen type, is known to grow better on sandy soils (DeLa Torre et al., 1996). Fraxinus ornus and Salix sp. would extendalong valley bottoms on deep soils and both, evergreen and de-ciduous Quercus, would develop in small stands likely mixed withpines. There would also be scarce open areas of grasslands andother herbaceous taxa, like Brassicaceae and Fabaceae.

To the top of the unit, forests show a rapid decrease, of pine andriparian woodlands in particular (Figs. 5 and 9), while there was anexpansion of grasslands. Investigations in nearby areas found areplacement of pine by Quercus ilex during the first half of the 5thmillennium cal BC (Carrión and van Geel, 1999), and in the BQTsequence there is in fact a small relative increase of the oak. Thewarmer and wetter conditions prevailing in Eastern Spain duringthis phase (Carrión, 2002; Cacho et al., 2010; Gil-Romera et al.,2010) may have favored the spread of Quercus.

One interesting finding is that the OM parameters that reflectpine (3-ring PA/2-ring PA and S/G ratios, Figs. 6 and 9) show highvalues even in samples for which the pollen record already in-dicates a landscape dominated by grassland. Thus, it is likely thatthere were still pine forests in the Pla de Les Alcusses well after theregional decline, reflected by pollen, had started. This is also inagreement with other local proxies, for example those indicative ofsoil erosion, fires and dry conditions (Fig. 9). The NPP suggest ahigher (forest) fire incidence before the local decline of pine; whileenhanced soil erosion and drier conditions are suggested once thelocal forest started to decline (Fig. 9). It is tempting to correlate this

Fig. 9. Selected proxies of environmental changes for the Neolithic period (unit V of the BQT sequence). First panel: in green colors pine, oak and riparian woodlands e from left toright; brown, shrubs; beige, herbs. NPP markers (see codes in SI_Table 1). 3-ring/2-ring PA ratio (see Table 4b). (For interpretation of the references to color in this figure legend, thereader is referred to the web version of this article.)

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shift in climate/environmental conditions with the transition phasethat occurred between 7.0 and 5.0 ka cal BP in the Mediterranean,indicated by Jalut et al. (2009).

Although, as discussed above, the pollen and NPP recordsalready suggest the presence of fires (mostly of the pine forest), thelow micro-charcoal content and the low abundance of molecularfire markers (Fig. 6) found in unit V point to a relatively low fre-quency, with a moderate impact on the landscape, in the absence ofevents of large intensity.

4.3.3. Unit IV (<5.6e5.3 to 1.7e1.5 ka cal BP)The age of the upper sample of unit V indicates that unit IV was

formed after 5.3 ka cal BP. Between 6.0 and 5.0 ka cal BP the climateof the Northern Hemisphere experienced a phase of instability andrapid change (Mayewski et al., 2004), to generally cooler conditions(Wanner et al., 2011). In the Mediterranean area, Jalut et al. (2009)defined the beginning of a third Holocene climate phase by5.5 ka cal BP characterized by increasing aridification. These con-ditions agree well with those inferred from the BQT record. Unit IVshows a sharp increase in carbonate content, a coarsening of thegrain size and increase in dense minerals (i.e. zircons; high Zrconcentrations), a change in the mineralogy of the less abundantmineral phases, a large decrease in microbial-derived OM, and asharp increase in proxies of burnt material (both molecular firemarkers and micro-charcoal). These properties point to arid, andpossibly cooler, climatic conditions. The inferred increase in soilerosion and sediment transport capacity also suggests increasedrainfall seasonality and torrentiality. Soil loss could also be relatedto the occurrence of intense fire events, as shown by the peaksappearing for the first time in the micro-charcoal sequence.

Nevertheless, pottery fragments found in this unit can beformally assigned to the late Iron Age (ca. 2.4e2.1 ka BP), while theage of the uppermost sample of this soil cycle fallswithin the Romanperiod. This suggests the presence of a large chronological hiatus inthe sequence and that landscape instability was the rule until theRoman period, or that the net effect of the phases of rapid climatechange in the mid-late Holocene (6.0e5.0, 4.2e3.8 and 3.5e2.5 ka cal BP; Mayewski et al., 2004) was soil erosion. In EasternSpain, formation of alluvial fans occurred at least since 4000 cal BP,

with catastrophic flood events around 2.8 ka cal BP (Ferrer García,2006). Intense sedimentation in the lower part of the catchmentsof the Ebro and Turia rivers was also found for the period 2.8e2.3 ka cal BP (Carmona and Ruiz, 2011; Constante et al., 2011). As aresult of the erosion, in the BQT sequence no environmental record(or only fragmentary) has been preserved from the late Neolithic tothe Roman period e a contrast with the archaeological remains inLes Alcusses area, which point to intense human occupation andlandscape exploitation during the late local Iron Age (Iberianperiod). Charcoal analysis of the nearby archaeological site of LaBastida de Les Alcusses (Fig. 1) offers additional information aboutlocal vegetation during the Iberian period (Pérez Jordà et al., 2011;Carrión Marco et al., 2012). The taxa identified in macro-charcoalfrom domestic contexts at the site suggest that a large variety ofplant specieswere collected in the surroundings of the village. Thesetaxa were mainly Aleppo pine, kermes/holm oak, Prunus, olive-oleaster, willow-poplar, heather and rosemary, among others. Thevery occasional occurrence of maritime pine is explained by theexistence of siliceous outcrops, suitable for the development of thisspecies, at the piedmont of the Serra Grossa, some 2 km away fromthe site. The set of taxa documented indicates the existence of pinewoodland with varied Mediterranean understory near the site.Although pine could have expanded in periods of greater aridity, weshouldnot rule out that itwaspart of thenatural vegetation, formingmixed forests together with holm oak.

4.3.4. Unit III (<1.7e1.5 to 1.6e1.4 ka cal BP)The unit corresponds chronologically to the end of the Roman

period and the early Middle Ages and its sedimentation may haveoccurred in a short period of time. Its properties indicate amoderateincrease in the degree of pedogenesis, but still low content ofmicrobial-derived OM, and a relative decrease in molecular firemarkers and in grain size. Taken together, they suggest that it mayhave developed under a wetter (possibly warmer) climate than theunderlying unit, and a more stable landscape. Wetter conditionswere inferred for this period (Ferrer García, 2006; Ferrer García andBlázquezMorilla, 2012), relating themtoan increase in the frequencyof storms due to predominant low pressures in the Mediterranean.

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4.3.5. Unit II (<1.6e1.4 ka cal BP e recent)This unit presents a lower degree of pedogenesis, a high soil OM

content with a relatively low content of microbial-derived OM, arelatively high abundance of plant-derived material (lignin), and alarge increase in micro-charcoal content. Its composition alsopoints to the application of agrochemicals, most likely associated tointense agricultural use in recent times: agrochemicals based onmetals and organic compounds (as organo-chlorinated biocides)were introduced in the last half of the 20th century (Li, 1999). Thedecrease in the degree of soil evolution can be interpreted as areturn to relatively arid-semiarid conditions, but the short time(centuries to decades) available for pedogenesis and the intenseagricultural use do not allow a proper evaluation.

4.4. Role of human activity on landscape change

The studied area is a relevant one for the understanding of theprehistoric developments occurring in Mediterranean Iberia duringthe Holocene. Evidence is provided by the abundant settlementsdated from the early Neolithic until the Roman period, which havebeen recorded both from excavations and surveys (Pascual Berlangaand García Borja, 2010). Eastern Spain is considered as one of themain settlement areas of pioneer populations of herder/farmers,from which the agricultural practices spread (Bernabeu and Martí,2012). In Les Alcusses there is evidence of an early Neolithic set-tlement (6th and 5th millennium BC), while a more intense occu-pation has been documented from the 4th millennium BC probablyrelated to the adoption of extensive agricultural practices(Bernabeu, 1995).

The pollen record of the base of unit V, showing the spread of U.parviflorus and, to a lesser extent, of the thermophilous shrublandconsisting of Pistacia terebinthus, Viburnum tinus, Phillyrea angus-tifolia or E. multiflora, suggests early human clearances (PeinadoLorca and Rivas-Martínez, 1987); while the presence of Cichoir-oideae, Plantago sp. and R. acetosa, and coprophilous fungi,although with low percentages, points to a slight impact of grazingactivities.

As already mentioned, the rapid decrease of the forest andspread of grasslands (and to a lesser extent of the shrubland) duringthe Neolithic (Fig. 5) may have been related to the expansion ofclearing activity. The increasing levels of coprophilous fungi likeGelasinospora (HdV1), Sordaria (HdV 55), Sporormiella (HdV 113)and Podospora (HdV 368), as well as Chaetomium (HdV 7A), linkedto fire and grazing, and C. ligniaria (HdV 172), related to regionalclearing processes, fire and dung, agrees with this interpretation.Also noteworthy are the high values of Glomus (HdV 207), pointingto erosive events as a result of deforestation and cropping activities.Additionally, Carrión and Dupré (1996) detect on these dates (5.0e4.6 ka cal BC) a progressive environmental eutrophication in thesequence of Navarrés, which could correlate with the increasinglevels of HdV 181 in the BQT sequence. Nevertheless, the compo-sition of soil OM suggests that the pine forest was still present in LesAlcusses area.

Human impact itself increases from the bottom to the top of unitV, as indicated by Cichorioideae. A wider extension of grasslandsallows a greater grazing pressure. The first palynological signals ofcultivation are provided by M. sativa and V. faba, which occurred atthe same time as the decline in the riparian woodland, pointing tothe use of these areas, close to watercourses, for this activity. Theabsence of pollen grains of Cerealia could be related to its limiteddispersal, as it would be likely cultivated in the vicinity of the site(López Sáez and López Merino, 2005). The continuous presence ofChaetomium suggests also a certain incidence of fire events. Cerealcultivation in the region is verified during the second half of 6thmillennium cal yr BC (7.5e7.0 ka cal BP) (Zapata et al., 2004).

Furthermore, a wide range of legumes has been found, and alsocereals, in Cendres archeological site (Martí, 1992; Buxó, 1997;Bernabeu et al., 2001), leading some authors to propose a simul-taneous or rotating cultivation of both crops (Buxó, 1991; Badalet al., 1994).

At the middle of unit V there is a significant change in the BQTsequence, coinciding with the minimum in (regional) arborealpollen. We, tentatively, correlate this change with the start of theclimate transition phase proposed by Jalut et al. (2009), and thusinitiated by 7.0 ka cal BP. The molecular proxies indicate a sudden,local, decline of the pine forest at Les Alcusses. But total arborealpollen slightly recovers to the top of the unit, mostly because of thesmall increase in deciduous Quercus, likely due to Quercus faginea,which would expand in shady places among holm oak (Q. ilex)forests (Peinado Lorca and Rivas-Martínez, 1987). Grazing pressurekeeps its levels, but the cultivation of legumes disappears in theuppermost sample. Despite the evidence provided by the bioticproxies, no geochemical proxy seems to point to significant changesin soil properties due to cultivation during the Neolithic.

The BQT sequence does not contain reliable environmental in-formation for the time between the late Neolithic (ca. 5.3 ka cal BP)and the Roman period (ca. 1.7 ka cal BP). The overall picture is thatof a change to arid conditions and a dramatic increase in fires. Thepresence of pottery remains assigned to the late local Iron Age(roughly 6the2nd centuries BC), as well as the presence of manyarchaeological sites of this phase found in Les Alcusses and itssurroundings (Fig.1), attest for an intensive exploitation of the land,which has been well documented by archaeological excavationsand surveys (Pérez Ballester, 2011). The settlement pattern wascharacterized by a heterarchical organization with fortified settle-ments acting as central places of small political territories thatruled over a number of secondary sites. The elites of these hill fortswere enormously competitive and land and exchange was one ofthe key factors for sustaining this power: extensive agriculturalexploitation existed at that time as the number, variety and qualityof agricultural tools suggest, e.g. those recovered at la Bastida de lesAlcusses, the best known Iron Age site in the area (Fig. 1; BonetRosado and Vives-Ferrándiz Sánchez, 2011).

The settlement pattern slightly changed from the 3rd and the2nd centuries BC when most of the hill forts were abandoned andsome others developed into larger settlements. Lowlands became akey area for the creation of new settlements, no doubt in connec-tion to the political economy and the exploitation of land resources.The Roman conquest of this part of the Iberian Peninsula at the endof the 3rd century BC unleashed historical changes and triggerednew economic developments into the 1st century BC. Broadlyspeaking, the indigenous fortified central places disappeared whileonly few of them developed into Roman cities that ruled over largerterritories. The rural occupation continued to be relevant andintense, as surveys in the study area have shown (Pascual Berlangaand García Borja, 2010), mostly in connection to long-distancedistribution of agricultural surplus through a new network of roads.

From the soil properties of units IV and III we cannot concludethere was agriculture in Les Alcusses in the time frame representedby them. Even more, unit III points to wetter conditions and acertain degree of carbonate leaching, which may agree with landabandonment or, at least, lower human pressure during the lateRoman period/Early Middle Ages. The top of unit II represents asubactual soil layer and the evidence of agrochemicals fits with thisinterpretation.

5. Conclusions

To our knowledge, the multiproxy approach followed in ourstudy has not been applied in any previous pedoarchaeological

R. Tallón-Armada et al. / Journal of Archaeological Science 47 (2014) 22e3836

investigation. We have combined disciplines and methods moretraditionally applied in archaeological contexts (geochemical andpollen studies) with other which are rarely used (micro-charcoalanalysis and pyrolysiseGC/MS). Themineralogical and geochemicalstudies provided information on the dominant processes in car-bonate soils and presence of particular chemical components,which helped to infer the role of Holocene climate as a driven soilforming factor and the imprints left by human activity (e.g. intensesoil cultivation). Pollen data, although specific for the Neolithiclayer, provided information on changes in the vegetation cover andcomposition (e.g. forest evolution), climate (e.g. aridification), firesand human activities (clearances, grazing pressure and cultivation).While micro-charcoal, with its highly contrasted record, reflecteddramatic changes in the fire regime. Finally, the study of the OMcomposition by pyrolysiseGC/MS provided clues on soil processes(type of soil OM, microbial-derived vs plant-derived), identificationof buried epipedons (i.e. residual lignin content), changes in thesource of the OM (3-ring PA/2-ring PA and S/G ratios in relation tothe presence of pine), and fires (i.e. burnt OM products).

The main results show a shift from wetter, in the early-midHolocene, to drier (aridification) climatic conditions andincreased fires, from the mid-late Holocene until present. We alsoinferred an increase in soil erosion, sediment transport capacity,increased rainfall seasonality and torrentiality since 5.3 ka cal BP.For the Neolithic period, the pollen record suggests a rapid decreaseof the forest and spread of grasslands coeval with the developmentof human activity. Grazing and legume cultivation were evidenced.Nevertheless, no soil property supports direct cultivation in theimmediate surroundings of BQT. Even more, the absence of cerealpollen in the sequence and the composition of the soil OM, pointingto the presence of pine despite its regional decline, should beinterpreted in the same way. Thus, this activity was probablycentered on riparian areas, instead of the slope soils. NPP andmolecular OM markers, which inform of local conditions, suggestthat the (local) forest suddenly collapsed around 7.0 ka cal BP.Therefore soil records e from paleosols and buried soils, inparticular e may provide clues to determine the spatial extent oflandscape dynamics and human activity inferred from regionalproxies.

The BQT sequence contains only fragmentary, direct, informa-tion on environmental change for the time span between the lateNeolithic (ca. 5.3 ka cal BP) and the Roman period (1.7 ka cal BP). Itseems that soil erosion during the periods of rapid climate changeof the late Holocene (6.0e5.0 ka, 4.2e3.8 ka, 3.5e2.5 ka) resulted inthe loss of the environmental record. Enhanced soil erosion after5.3 ka cal BP may have also been due to the intensification of soiluse during the late local Iron Age, as suggested by the increase infires and the archaeological remains in the area. A certain climateamelioration is suggested for the Roman period (soil unit III) withintense agricultural use only reflected by the upper soil unit studied(with the possible use of agrochemicals).

Our results indicate that a multiproxy approach enables a betterinterpretation of soil sequences in terms of dominant environ-mental conditions (climate and human activity) and provides abetter possibility of contextualizing them with available re-constructions of Holocene environmental change in the WesternMediterranean.

Acknowledgments

This study was funded by the European Research Council(Advanced Grant No. 2305619, project ‘AGRIWESTMED: Originsand spread of agriculture in the western Mediterranean region’)and the Diputación de Valencia-Museo de Prehistoria de Valencia(2009/CI585). Daniel Abel Schaad and Judith Schellekens were

supported by AGRIWESTMED project. We thank Ward Chesworth(Professor Emeritus of the School of Environmental Sciences, Uni-versity of Guelph) for his comments and suggestions of an earlierversion of this document.

Appendix A. Supplementary data

Supplementary data related to this article can be found at http://dx.doi.org/10.1016/j.jas.2014.03.023.

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