The timing of postglacial coastal adaptations in Eastern Iberia: A Bayesian chronological model for the El Collado shell midden (Oliva, Valencia, Spain)

Quaternary International xxx (2015) 1e12

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The timing of postglacial coastal adaptations in Eastern Iberia: A Bayesian chronological model for the El Collado shell midden (Oliva, Valencia, Spain)
ndez-Lo
pez de Pablo a, b, * Javier Ferna a b

 de Paleoecologia Humana i Evolucio
social (IPHES, Spain), Campus Sescelades Edifici W3, 43007, Tarragona, Spain Institut Catala  ria, Universitat Rovira i Virgili, av. Catalunya, 35, 43002, Tarragona, Spain Area de Prehisto

a r t i c l e i n f o

a b s t r a c t

Article history: Available online xxx

El Collado is an open air site containing evidence of 14 burials and a shell midden archaeological deposit with different phases of human occupation dated to the Early Holocene. Previous studies have produced 14 radiocarbon dates using bone collagen samples from human burials. However, no attempt has been made to date the stratigraphic sequence to address the formation time of the shell midden and establish a chrono-stratigraphic framework for the study of bio-archaeological and cultural assemblages. We critically evaluate the available radiocarbon record of the site and present 6 new AMS radiocarbon dates on ungulate bones with anthropic fractures and bivalves from the three major stratigraphic horizons. Then, we integrate our results with previously published AMS radiocarbon determinations on human samples into a chronological Bayesian model, constraining the radiocarbon distributions with prior information about the samples stratigraphic provenance. Finally, we correlate the results of the chronological model with the regional archaeological sequence and the available data on coastal evolution at regional and local scales. The vertical distribution of the radiocarbon dates makes evident some stratigraphic disturbance caused by the repeated presence of pit graves, agricultural activities and low stratigraphic control of the excavation process. However, once the problematic determinations are identified as outliers, the remaining radiocarbon dates grouped according the major stratigraphic divisions, and the calibrated distributions modelled-constrained, the resulting Bayesian phase model reveal high agreement index (Ac ¼ 103). The shell midden formation took place from the bottom of the sequence, spanning 1022e1965 calibrated years (CI 95.4%). The occupations documented at Phase 1 (Level IV) are dated to the Early Holocene (9828e9551 cal BP). The Phase 2 (Level II), encompass radiocarbon evidence of both burial and occupational activities dated to 9437 to 8477 cal BP, spanning 779e985 calibrated years (CI 95.4%). Finally, the Phase 3 (Level I) records Late Mesolithic occupations deposited between 8509 and 8391 cal BP for the start boundary and 8499e8060 cal BP for the end boundary (CI:95.4%). There are no individual radiocarbon dates during or postdating the chronological span of the 8.2 ka climatic event (8300e8140 cal BP). © 2015 Elsevier Ltd and INQUA. All rights reserved.

Keywords: Shell middens Radiocarbon chronology Early Holocene Mediterranean Mesolithic Iberian Peninsula

1. Introduction Unlike Atlantic Europe, there is very little evidence of coastal shell middens dated to the Epipaleolithic and Mesolithic periods in the Mediterranean basin. Although the presence of genuine shell mounds has been recently reported in the coast of Tunisia

 de Paleoecologia Humana i Evolucio
Social (IPHES), Campus * Institut Catala Sescelades Edifici W3, 43007, Tarragona, Spain. E-mail address: [email protected].

(Mullazzani, 2013), most of the Mediterranean shell middens come from small archaeological deposits in caves and/or rock shelters (Colonese et al., 2011). The Iberian Mediterranean region exemplifies the low preservation of coastal shell middens due to the Early Holocene flooding of the coastal platform and the subsequent agricultural and urban pressure on littoral fringes. Shell middens dated to the Upper Magdalenian and the Epipaleolithic periods are known in few cave
laga (Aura et al., 2013), although the deposits on the coasts of Ma best case study is Nerja cave (Jord
a et al., 2011). In addition to these examples, the archaeological record is chronologically and

http://dx.doi.org/10.1016/j.quaint.2015.10.077 1040-6182/© 2015 Elsevier Ltd and INQUA. All rights reserved.


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pez de Pablo, J., The timing of postglacial coastal adaptations in Eastern Iberia: A Bayesian Please cite this article in press as: Ferna chronological model for the El Collado shell midden (Oliva, Valencia, Spain), Quaternary International (2015), http://dx.doi.org/10.1016/ j.quaint.2015.10.077


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geographically sparse. In the central valleys of the Alicante province, only Santa Maira cave has provided preliminary evidence of the exploitation of intertidal shellfish and fishing activities from the Upper Magdalenian to Mesolithic (Aura et al., 2006, 2015). The location of this site 30 km inwards from the present coastline, however, suggests indirect access to marine resources, probably as a result of visits from other coastal extraction or residential camps, into a broader settlement pattern. In this context, the open-air archaeological site of El Collado (Oliva, Spain) is exceptional because of its coastal location, rich archaeological deposit with shell middens along with faunal and lithic assemblages, and 14 associated human burials (Aparicio, 2008, 2014). From its excavation in the late 1980s, different studies have analysed the Mesolithic burial practices, paleodiets, lithic assemblages and the radiocarbon record of the human remains. The zooarchaeological, archaeomalacological and ichtyological assemblages have remained unstudied until now, however, in part because none of the previous studies addressed the chronology of the shell midden along the different occupation episodes. Therefore, building robust chronologies for the El Collado site is of major interest to study the last hunter gatherers' coastal adaptations in the Mediterranean region of Spain, and also provides a chronological framework for future studies of the bioarchaeological collections. Here, we present the first of two interrelated works aiming to study the exploitation patterns of intertidal resources at El Collado. In this work we will focus on the reconstruction of the chronostratigraphy, evaluating previous works on the site's radiocarbon record, and producing new AMS radiocarbon dates to fix previous biases in sample selection. In addition, we will build a chronological Bayesian model grouping the radiocarbon dates into three major stratigraphic divisions. Finally, we will correlate the results of our phase model with the regional archaeological sequence and the available data on coastal evolution at regional and local scales. 1.1. Site description The open-air site of El Collado is located in the municipality of Oliva (Valencia) at the southern sector of the Valencian gulf in eastern Spain. This sector of the Iberian Mediterranean coast exhibits a gentle progradational shelf with a strong subsidence rate, producing an onlapping retrogradational deposition of successive transgressive sea level peaks from the Late Pleistocene onwards. Beginning in the Late Pleistocene, the coastal morphology was dominated by the formation of beach barriers and lagoons (Rey and Fumanal, 1996). The coastal evolution indicates a progressive rise in the sea level from the Late Glacial interestadials that was interrupted during the Younger Dryas when the sea level was 60 m lower than today (Albarracín, 2014). During the Early and Middle Holocene, a marine transgressive process led to the flooding of terminal coastal plains along the development of fresh water ~ als and Fumanal, 1995). swamps and brackish lagoon biotopes (Vin The site lies 70 m.a.s.l., on the south-eastern slope of a small Cretaceous relief unit that forms part of the Betic chain, and approximately 5 km north of the Pego-Oliva marsh (Fig. 1). The El Collado site was discovered at the beginning of the XXth century , 1916), although archaeological excavations were not un(Bosca dertaken until much later, between 1987 and 1988, by J. Aparicio over a surface of 143 m2 (Fig. 2). The excavation results were published in a monographic volume (Aparicio, 2008) along with the lithic assemblages and different studies about the human osteological collections. El Collado is known by its funerary record, which is composed of 14 Mesolithic pit burials that delivered human remains of 15 individuals associated with a shell midden archaeological deposit.

However, there is very little description of the site stratigraphy. Despite the lack of specific geomorphological and sedimentary studies, the site location and the photographs (Aparicio, 2008: 105e117, illustrations 23e24) of the stratigraphic profiles suggest the site was formed by colluvial and anthropic depositions. The archaeological deposit ranges between 1 and 1.5 m depth and contains three major archaeological levels according to Aparicio (2008: 24 and Fig. 4):  Level I, formed by a blackish-grey sediment with an approximate depth of 1.5 m that was disturbed by agricultural activities. The lithic assemblages present trapezoidal microliths, microburins and laterally notched blades indicating a Mesolithic IIIA-B chrono-cultural attribution.  Level II consists of dark brown clayey-compacted undisturbed sediments of approximately 1 m depth. The lithic assemblages are dominated by flakes and notched and denticulated tools, whereas endscrapers and burins are minimally represented.  Level III is described as clayey reddish sediment located at the bottom of the archaeological sequence. There is no specific information regarding the depth of this level in the general description of the stratigraphic sequence. Based on the pictures of the stratigraphic section called “corte b-c” (Aparicio, 2008:111), we estimate a variable depth between 0.1 and 0.3 m. The lithic assemblages of this level consist of backed bladelet tools burins and endscrapers, exclusively found at the excavation unit G-III, indicating a Mesolithic I chrono-cultural attribution. There are several inconsistencies in the general description of the site stratigraphy and the attribution of lithic assemblages to each level that requires clarification. First, there is an additional level called Level IV not referenced in the description of the stratigraphic sequence (Aparicio, 2008: 24) but cited in the inventory of archaeological materials (Aparicio, 2008: 52e55) and the conclusions chapter (Aparicio, 2008:350e353). This Level IV is also referenced in the bag labels of the archaeological materials deposited at the Prehistory Museum of Valencia that we have analysed, where it is described as “Nivel IV, Tierra roja base”. Actually, what it is referred to as Level III in the general description of the stratigraphy includes both materials attributed to the Level III (of reddish-brown sediment referred by aparicio as “m-r”) and materials attributed to Level IV (reddish sediment), (Aparicio, personal communication, 24/1/2012). Fig. 3 represents the corrected stratigraphic sequence for the sampled excavation units (see below). Second, the chrono-cultural scheme used by Aparicio was based on his previous research on the Mesolithic in eastern Spain (Aparicio, 1979), but such a chronological model is not currently used by Iberian archaeologists. Therefore, we will rely on more recent bibliography concerning Early Holocene regional archaeological sequences (Martí et al., 2009; Aura et al., 2011) to correlate our radiocarbon results with previous descriptions of the El Collado stratigraphy and lithic typology (see below Sections 3 and 4). 1.2. Radiocarbon record Two different studies have previously analysed the radiocarbon chronology of the El Collado site using samples of bone collagen from human burials (Table 1). First, Aparicio dated burials 4, 6 and 13, obtaining 4 conventional radiocarbon determinations produced in the radiocarbon laboratory at the University of Barcelona (Aparicio, 2008). In a recent work, those dates were calibrated using a terrestrial calibration curve (Aparicio, 2014), but palaeodietary analyses were not considered so it was not possible to assess whether a marine reservoir effect may have been present. In


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~ als and Fig. 1. The location of the El Collado site in the Southern Sector of the Valencian Gulf, Spain. The location of a simplified Flandrian coastline has been adapted from Vin Fumanal (1995: Fig. 5).

addition, the high BP age standard deviations of some dates produced broad calibration ranges. Despite the above mentioned problems, the first series of conventional radiocarbon ages revealed different chronologies, suggesting long use of the site as a cemetery during the Early and Late Mesolithic.

Table 1 Conventional and AMS

14

Context

Sample

Burial Burial Burial Burial Burial Burial Burial Burial Burial Burial Burial Burial Burial Burial

Human Human Human Human Human Human Human Human Human Human Human Human Human Human

4 6 13 13 1 3 4 5 6 7 9 11 12 13

Gibaja et al. (2015). It should be noted, that the % yields are low (<1%) for some of the human samples. However, the C:N ratios
et al., 2006) for the reported in a previous study (García-Guixe same individuals that were sampled for AMS radiocarbon dating are appropriate.

C radiocarbon determinations on bone collagen from human samples of the El Collado site published in previous studies.

bone bone bone bone bone bone bone bone bone bone bone bone bone bone

Lab. Ref

14

UBAR-927 UBAR-928 UBAR-280 UBAR-281 1619.1.1 1620.1.1 1621.1.1 1622.1.1 1623.1.1 1624.1.1 1625.1.1 1626.1.1 1627.1.1 1628.1.1

8690 8080 7570 7649 8067 8388 8491 7992 8166 8319 7801 7742 7900 7976

C Age BP ± ± ± ± ± ± ± ± ± ± ± ± ± ±

100 60 160 120 34 36 37 34 35 35 38 35 32 32

d13C

d15N

Marine diet %

d13C

Yield

C:N

Reference

nd nd nd nd 19.5 17.6 17.6 18.2 18.2 17.9 nd nd 19 18.1

nd nd nd nd 10.2 10.2 12.8 10.6 10.9 8.9 nd nd 9.5 10.4

nd nd nd nd 0 25 25 17 17 21 13.5 13.5 7 19

nd nd nd nd 20.5 21.9 22.4 17.8 20.9 18.9 26.6 22.8 14.7 17.2

nd nd nd nd 0.21 1.69 1.09 0.14 2.25 0.45 0.12 0.14 0.33 0.57

nd nd nd nd 3.4 3.2 3.4 3.3 3.3 3.4 nd nd 3.5 3.3

Aparicio (2008) Aparicio (2008) Aparicio (2008) Aparicio (2008) Gibaja et al. (2015) Gibaja et al. (2015) Gibaja et al. (2015) Gibaja et al. (2015) Gibaja et al. (2015) Gibaja et al. (2015) Gibaja et al. (2015) Gibaja et al. (2015) Gibaja et al. (2015) Gibaja et al. (2015)

A second study produced AMS radiocarbon determinations from 10 different burials (Gibaja et al., 2015). The radiocarbon samples were analysed at the Accelerator Mass Spectrometry facilities in the Centro Nacional de Aceleradores (Seville, Spain). Table 1 provides palaeodietary data of the dated individuals (d13C, d15N and % of marine diet) based on the information published in a
et al., 2006). The table also contains previous study (García-Guixe the quality control measurements (d13C and Yield) of the samples analysed in the Centro Nacional de Aceleradores as reported by

The radiocarbon results were calibrated using a mixed marineterrestrial calibration curve (Reimer et al., 2013), considering the percentage of marine diet for each individual inferred from a pre
et al., 2006). Despite the lack of pubvious study (García-Guixe lished DR for the central Mediterranean region of Spain, Gibaja et al. (2015) considered a DR ¼ 94 ± 61 calculated from the Marine Radiocarbon database (Reimer and Reimer, 2001) on the basis of previous work undertaken in other Mediterranean regions (Siani et al., 2000; Reimer and McCormac, 2002). The Bayesian phase


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pez de Pablo, J., The timing of postglacial coastal adaptations in Eastern Iberia: A Bayesian Please cite this article in press as: Ferna chronological model for the El Collado shell midden (Oliva, Valencia, Spain), Quaternary International (2015), http://dx.doi.org/10.1016/ j.quaint.2015.10.077

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midden; (b) compare the site's chronology with the local and regional data on the coastal evolution; and (c) independently establish diachronic and synchronic relationships between the cemetery and the human occupations. In this work, we present the first systematic study of El Collado chrono-stratigraphy, in the framework of the research project POSTGLACIAL-MED Environmental dynamics and human responses during the Postglacial in the Mediterranean façade of Iberia (ca. 12700e8000 cal BP). We present 6 new AMS radiocarbon dates on short lived samples from previously undated stratigraphic horizons. In addition, we integrate the new and previous radiocarbon determinations to produce a completely new Bayesian chronological model using prior information on the stratigraphic provenance of the dated samples. Finally, we discuss our results about the formation time of the shell midden first, and the available data on the coastal evolution at a regional scale. 2. Materials and methods

Fig. 2. Plan of the El Collado site (after Aparicio (2008), modified) with the location of the sampled excavation units and the Mesolithic burials.

modelling of the radiocarbon results indicated that all of the dated funerary activity took place over almost a millennium (781e1020 years at 95.4%) and was restricted to the Early Mesolithic period (Gibaja et al., 2015). There have been no previous attempts to date the archaeological sequence using radiometric methods. As noted above, the available radiocarbon dates for human samples indicate that the funerary activity was stratigraphically associated with Level II and chronologically restricted to the Early Mesolithic period; however, the chronology of the human occupations at the site from the bottom (Level IV) to the top (Level I) of the archaeological sequence remains unknown. Considering the shell matrix nature of the site's archaeological deposits along the different occupational horizons, building robust chronological frameworks is essential to (a) identify the formation time and chronological limits of the El Collado shell

In this work, we have followed the recommended conventions for reporting radiocarbon date results (Millard, 2014). Therefore, in addition to defining our sampling strategy for dating the stratigraphic sequence, we taxonomically describe the radiocarbon samples as well as the pretreatment procedures and the sample quality control indicators. Finally, as this work aims to produce a chronological Bayesian phase model, in the results section, we report the calibration of individual dates as both unmodelled and modelled (or stratigraphically constrained) distributions. 2.1. New AMS radiocarbon dates: sample selection, pretreatment, quality control indicators One of the main problems of the El Collado site is the paucity of information about the excavation process and the site stratigraphy published in previous studies (Aparicio, 1992, 2008, 2014). Prior to sample selection, we attempted to reconstruct as far as possible the archaeo-stratigraphic deposit using the published stratigraphic descriptions and the stratigraphic references labelled in the bags of bio-archaeological materials deposited in the Prehistory Museum of Valencia. We started with a careful examination of the inventory numbers of the archaeological materials associated with each excavation unit during each one of the fieldwork seasons. We restricted our selection according two criteria. First, we avoided

Fig. 3. Stratigraphic section D-E from the El Collado site (modified after Aparicio (2008): Anexo Fig. 5) with the boundaries of the major stratigraphic levels (left) and the subdivisions in horizontal layers.


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those excavation units containing or touching burials, considering that pit graves could have severely disturbed the depositional conditions by mixing materials originating at different chronocultural horizons. Second, we focused on those excavation units with the highest number of stratigraphic divisions and materials. Applying both criteria, we identified two areas of higher potential that, for the purposes of this work, we have called trench 1 and trench 2. Trench 1 consists of the excavation units FIII, FIV and FV and GIII, covering the two fieldwork seasons and the entire site stratigraphic sequence of Levels I, II and IV. The absence of Level III in the stratigraphic sequence of trench 1 should be noted. According to the list of lithic artefacts published in the site monography and the inspection of the inventory numbers of the materials deposited in the Prehistory Museum of Valencia, the materials assigned to or labelled as Level III were spatially restricted to excavation units IeIII, IeII, IeI, K-III, K-II and K-I. From top to bottom, the stratigraphic series for the trench 1 begins with Level I, which was associated to layers C-1, excavated during the first fieldwork season. Level II was subdivided in 5 different layers (C-2, IIA, IIB, IIC and IID), each of 0.2 m depth as noted on the bag labels of the faunal and mollusc assemblages. Finally, at the bottom of the sequence, we found the materials labelled Level IV, “tierra roja base”. Both Levels II and IV were excavated during the second fieldwork season. Four radiocarbon samples were selected from Layers C-1, IIB and IV: two bone samples of red deer (Cervus elaphus) with anthropic fractures from Layers I and IIB, and a sample of Cerastoderma glaucum and another one of red deer from Layer IV, associated with the reddish deposits at the bottom of the archaeological sequence. A detailed description of the radiocarbon samples along with their stratigraphic and spatial provenance is detailed in Table 2.

5

Table 3 Synthetic correlation between the major stratigraphic divisions of the El Collado site and the subdivisions in layers (according to the excavation bag labels) in the sampled trenches. Major

Trench 1

Trench 2

Stratigraphic Divisions Level I

(FIII, FIV, FV, GIII) Layers C-1

(H1eH2) Layers C-1

C-2

C-2

N IIA

C-3

N IIB

C-4

N IIC

No data

Level II

N IID Level IV

IV

Six new radiocarbon samples were analysed at two different laboratories. Samples Beta-337786, Beta-337187 and Beta-323495 were produced at the Beta Laboratory in Miami. The bone samples were washed with deionized water and the surfaces scraped free of the outermost layers and then crushed. Once the mineral fraction was eliminated with cold HCl (hydrochloric acid), the resulting collagen was dissected and inspected for rootlets. Unique prescription of cold 1% sodium hydroxide (50/50 wt% NaOH) was applied to remove secondary organic acids. The ultra-filtration method was not applied in the bone collagen samples sent to

Table 2 Stratigraphic provenance, taxonomic description and laboratory sample identification of the new AMS 14C radiocarbon dates produced in this study. The MPV nº denotes the inventory number of the Prehistory Museum of Valencia. Layer

Square

Label date

MPV nº

Species

Fragment

Lab. Reference

C-1 C-1 II B C-4 IV IV

H1eH2 F/III-GIII F/III, IV, V H1eH2 F/III-IV-V F/III-GIII

24/11/1987 09/02/1989 14/01/1989 16/12/1987 1989 12/01/1989

2279 2326 12457 2232 13667 13657

C. C. C. B. C. C.

Phemur Diaphysal Metatarsal 2nd phalanx Antler Valve

UBA-27478 Beta-337186 Beta-337187 UBA-27477 UBA-27479 Beta-323495

On the other hand, trench 2 is composed of the excavation units H1-H2, excavated during the first fieldwork season to a depth of 1 m, according to a published picture of a stratigraphic section of the adjacent excavation units I-1 and I-2 (Aparicio, 2008, Fig. 23). The excavation units H1 and H2 were excavated in artificial spits (C1, C-2, C-3 and C-4) of approximately 0.2 m depth. A tentative correlation between the layers and stratigraphic horizons can be established using the photographic documentation representing the major stratigraphic limits (Aparicio, 2008:111). On the basis of Aparicio's description, the materials labelled C-1, recovered during the first fieldwork season at the excavation units H1eH2, must be related to Level I (Aparicio, 2014:342). The spits C-2, C-3 and C-4 should be related with the Level II considering their provenance from the first fieldwork season too. Table 3 presents a correlation between both trenches sampled. Layers C-1 would be correlated with Level I (light greyish deposit), whereas C-2, C-3 and C-4 would correspond with Level II (dark grey). We selected a bone collagen sample of C. elaphus from layer C-1 at the top of the sequence, and another one of B. primigenius from layer C-4.

elaphus elaphus elaphus primigenius elaphus glaucum

Beta Analytic. On the other hand, the sample of C. glaucum shell was pretreated using the acid etch protocol. The shell was first washed in deionized water, removing associated organic sediments and debris where present. The valve was then crushed and repeatedly subjected to HCl etches to eliminate secondary carbonate components. The other three radiocarbon determinations, UBA-27478, UBA-27474 and UBA-27479, were produced at the 14CHRONO laboratory at Queen's University, Belfast. The pretreatment methods employed by this laboratory on bone collagen samples are fully described in a recent publication (Reimer et al., 2015), involving “a simple ABA treatment followed by gelatinization (After Login 1971) and ultrafiltration (Brown et al., 1988) using a Vivaspin® cleaning method introduced by (Bronk Ramsey et al., 2004)” (Reimer et al., 2015:4). Radiocarbon ages were determined with a NEC compact model 0.5 MV Accelerator Mass Spectrometer. In addition, for each sample, d13C and d15N isotope ratios were obtained using a Thermo Delta Isotope Ratio Mass Spectrometer with Flash EA to obtain bone collagen quality control indicators (%yield, C:N). A collagen yield of less than ~1%


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means that the sample was not well preserved and is unacceptable for dating purposes. 2.2. Calibration procedures and Bayesian chronological modelling Radiocarbon results were calibrated and analysed using Oxcal 4.2 software (Bronk Ramsey et al., 2010). We used the IntCal 13 curve for the calibration of bone collagen samples of ungulates and the Marine 13 curve (Reimer et al., 2013), with the local DR ¼ 94 ± 61 previously discussed, for the sample of C. glaucum. It should be noted that C. glaucum is a filter feeding bivalve that inhabits coastal lagoons and estuaries with limited wave action (Ivell, 1979). Therefore, the marine reservoir effect should not be exactly the same than that produced by coastal lagoons which may have substantial quantities of freshwater. Conversely, the radiocarbon samples of human bone collagen were calibrated using a mixed marine-terrestrial calibration curve considering the percentage of marine diet derived from a previous
et al., 2006) and the local DR ¼ 94 ± 61 (as study (García-Guixe described in Gibaja et al., 2015). One of the advantages of using Oxcal 4.2 lies in its capability to integrate radiocarbon ages calibrated with both marine and atmospheric curves into the same chronological model. We conducted a Bayesian phasing model to integrate previous AMS radiocarbon dates for human bone collagen with the new determinations produced in this study into a comprehensive stratigraphic scheme. Bayesian chronological analysis provides a probabilistic framework to integrate radiocarbon data with prior information about a site's stratigraphy. Its advantage regarding other inferential statistical techniques lies on its model based focus (Buck et al., 1996) for explicitly grouping dates in phases according to their relative stratigraphic order. Oxcal 4.2 can generate two main model types, called Sequence and Phase, to analyse archaeological chrono-stratigraphic sequences according to different assumptions. Phase is a model type that groups dated events formed by one coherent group in a given context, but for which there is no information regarding the internal ordering (Bronk Ramsey, 2011). Oxcal is also equipped with indices to evaluate the model's consistency: the Agreement and Convergence indices (Bronk Ramsey, 2009a). The Agreement indices are expressed in terms of likelihoods measuring how well the prior model agrees with the observations. There are four types of agreement indices, but for the purposes of this case study, we will focus on two of them: the individual agreement index A, which identifies whether individual samples agree with the model if its value is over 60%; and the model agreement index Amodel, which is used to test whether the entire model agrees with the given data. The Amodel should be over 60% to validate the model against the data. The convergence index C measures the degree to which a truly representative solution has been generated by the model when the program implements Monte Carlo Markov Chain iterations (Bronk Ramsey, 2009a: 353e357). To validate the model robustness, the convergence C values should be higher than 95%. Finally, Oxcal is equipped with a set of modelling tools such as the Outlier() command, which allows it to identify those problematic dates that violate the stratigraphic order excluding them from the chronological model; or the Outlier analysis, an averaging method which assumes the same prior probability of being outliers for all the radiocarbon dates considered in a given model to produce down weighted posterior probability distributions (Bronk Ramsey, 2009a) All of these analytical capabilities and indices make Oxcal a suitable tool for building

robust chronologies on shell midden sites with complex depositional histories (Kennett and Culleton, 2010; Bicho et al., 2013; Thakar, 2014; Wicks et al., 2014). For this work, we have produced a three-phase Bayesian sequential model of El Collado chrono-stratigraphy using 16 AMS radiocarbon determinations. In this chronological model, we have integrated the 10 AMS radiocarbon determinations from human burials obtained in a previous study (Gibaja et al., 2015) with the 6 new dates presented here on trenches 1 and 2. Given the impossibility to assess the marine contribution to diet, we do not include the radiocarbon dates published by Aparicio (2008) in this model. We set up a three phase model according to the major stratigraphic divisions of the site (Levels I, II and IV), assuming a sequential order amongst the three phases. Therefore, we explicitly acknowledge that one phase follows the other but we do not assume an a priori contiguous deposition model. We consider both assumptions best describe the site depositional conditions according to the stratigraphic information currently available about the archaeological deposit. The new three-phase Bayesian sequential model has been implemented following two steps. First, we have produced an outlier analysis using an Outlier model General t-type, assuming each date has a 5% prior probability of being an outlier. This step has allowed the identification of the model outliers according to their posterior probability. Then, the dates clearly identified as outliers have been removed from the model using the Outlier () command and we have run the model again, checking the consistency of the results with the individual and model agreement indices. Such a two-step model implementation is recommended for the manual rejection of outliers (Bronk Ramsey, 2009b:3). Finally, we further interrogate the resulting modelled phases using the Span (), Interval () and Sum () commands. We use the Span() command to determine probabilistically the temporal duration of the whole sequence whereas we use the Interval () within each phase to infer the difference between the start and end boundaries of each modelled phase. Finally, we then use the Sum () function to visualize variations on the summed probability distributions within each modelled phase.

3. Results 3.1. Radiocarbon results The radiocarbon results are presented in Table 4. The bone collagen from all of the samples dated at the 14CHRONO laboratory at Queen's University, Belfast, is well preserved, meets the published collagen quality indicators, and has a collagen yield higher or close to 1% (Van Klinken, 1999). In trench 1, the vertical distribution of the radiocarbon dates reveal problems of stratigraphic disturbance. In this area, three of the four radiocarbon determinations show inconsistent results regarding their stratigraphic position. In Level IV, the two dates differ more than 1000 BP years, with the determination of C. glaucum (Beta-323495) being older than the radiocarbon sample of C. elaphus (UBA-27479). According to the excavation dates preserved on the bag labels, and especially the presence of red clay from the bottom of the deposit attached to the inner and external surfaces of the dated valve, we believe that the date Beta-323495 (9020 ± 40 BP) is in correct stratigraphic position. Thus, the sample UBA-27479 of bone collagen of C. elaphus should be considered intrusive in this context.


ndez-Lo
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ndez-Lo
pez de Pablo / Quaternary International xxx (2015) 1e12 J. Ferna Table 4 New AMS

7

14

C radiocarbon results of the El Collado site archaeological deposit. All dates were calibrated in Oxcal 4.2 and are expressed as unmodelled chronological ranges.

Context

Sample ID

Species

d13C

d15N

C:N

Yield

14

Layer C-1 Layer C-1 Layer II B Layer C-4 Level IV Level IV

UBA-27478 Beta-337186 Beta-337187 UBA-27477 UBA-27479 Beta-323495

C. C. C. B. C. C.

19.7 19.9 20.08 18.2 20.3 2.0

4.1 nd nd 5.0 3.7 nd

3.27 nd nd 3.23 3.26 nd

2.60 nd nd 0.97 1.90 nd

7660 7820 7610 8292 7939 9020

elaphus elaphus elaphus primigenius elaphus glaucum

At the top of the stratigraphic sequence, the radiocarbon ages Beta-337186 (7820 ± 30 B P) from Layer C-1 and IIB Beta-337187 (7610 ± 30 BP) are inverted, the former being 210 BP years older than the latter. It is difficult to evaluate the origin of that inversion; the most parsimonious explanation is that it is due to a combination of the reiterative use of this area for digging pit graves during the Mesolithic and the post-depositional processes caused by recent agricultural use. At trench 2 (excavation units H1 and H2), the two radiocarbon determinations show consistent results regarding its stratigraphic position: in layer C-1 the radiocarbon date UBA-27478 (7660 ± 44 BP) and in layer C-4 the date UBA-27477 (8292 ± 57 BP). 3.2. Bayesian chronological analysis In our Bayesian phase model, Phase 1 represents the development of Level IV and consists of two radiocarbon dates. The oldest age (Beta-323495) is securely attributed to the red matrix deposit, whereas the younger layer (UBA-27479) is probably intrusive to the context as it is confirmed by the posterior probability given by the outlier analysis (P ¼ 100). Phase 2 groups twelve radiocarbon determinations stratigraphically associated with Level II. Ten of them correspond to AMS radiocarbon dates from human samples, whereas the remaining two are samples of Bos primigenius (UBA-27477) and Cervus elaphus (Beta-337187). As discussed elsewhere (Gibaja et al., 2015), the stratigraphic association of human burials with Level II was established by Aparicio (Aparicio, 2008). As mentioned before, using a sequence phase model, we assume there is no inner stratigraphic ordering amongst the samples associated with Phase 2;

C Age BP ± ± ± ± ± ±

44 30 30 57 44 40

cal BP 1s 8514 8629 8419 9420 8971 9671

cal BP 2s 8404 8561 8387 9145 8649 9497

8542 8685 8449 9461 8984 9815

8391 8541 8372 9123 8637 9444

however, the sample Beta-337187 should be considered anomalous to this context considering the posterior probability given by the outlier analysis (P ¼ 37%). Finally, phase 3 represents Level I. It consists of two radiocarbon determinations on Cervus elaphus from layer C-1: UBA27478 and Beta-337186. Both radiocarbon dates show unmodelled calibration ranges (at the 95% CI) that are statistically different. The radiocarbon date Beta-337186 is older and, likely, represents an intrusion produced by the vertical displacement of materials from the underlying Level II in trench 1. The outlier analysis (P ¼ 86%) confirms the spurious relation of this date regarding its context if we assume that the chronological differences between the samples UBA-27478 and Beta-337186 are not directly related with the fact that the former was ultra-filtrated whereas the second not. The results of the Outlier analysis, used for the outlier detection, are presented in Table 5, whereas the model results of the second step are presented in Table 6 and graphically displayed in Fig. 4, which plots the modelled radiocarbon distributions of each date and the start and end boundaries of each modelled phase. The individual agreement (A) and convergence (C) indices for each date are presented in brackets. The three radiocarbon determinations identified as outliers are graphically represented but they do not have individual agreement index values because they were not computed into the model. For the entire sequence, the model agreement index Amodel ¼ 103 and falls well above the 60% critical threshold. The individual agreement indices range between 82 and 111, falling well above the 60% level. In addition, all of the individual and phase convergence values [C] are above the 95% level, displaying good agreement with the model.

Table 5 Results of the El Collado site phase model using an Outlier analysis General t-type assuming each date has a 5% prior probability of being an outlier. Phase

Phase 3

Phase 2

Phase 1

14

Sample ID

Provenience

Boundary UBA-27478 Beta-337186 Boundary Boundary 1626.1.1 Beta-337187 1625.1.1 1627.1.1 1622.1.1 1628.1.1 1619.1.1 1623.1.1 UBA-27477 1624.1.1 1620.1.1 1621.1.1 Boundary Start 2 Boundary End 1 UBA-27479 Beta-323495 Boundary Start 1

End of Level I deposition C-1 C-1 Beginning of Level I deposition End of Level II deposition Burial 11 Layer II B Burial 9 Burial 12 Burial 5 Burial 13 Burial 1 Burial 6 Layer C-4 Burial 7 Burial 3 Burial 4

7742 7610 7801 7900 7992 7976 8067 8166 8292 8319 8388 8491

Level IV Level IV

7939 ± 44 9020 ± 40

C BP age

7660 ± 44 7820 ± 30

± ± ± ± ± ± ± ± ± ± ± ±

35 30 38 32 34 33 37 35 57 35 30 37

Modelled 68% range cal BP

Modelled 95.4% range cal BP

8480 8474 8493 8493 8507 8543 8580 8587 8702 8861 8761 8580 9080 9395 9259 9390 9446 9484 9608 9686 9665 9794

8494 8513 8505 8532 8544 8579 9119 8600 8931 8974 8955 8634 9135 9436 9315 9402 9489 9575 9729 9910 9802 10213

8252 8377 8336 8389 8401 8466 8380 8488 8598 8639 8632 8490 8995 9141 9135 9243 9302 9347 9436 9479 9505 9518

7893 8032 8005 8123 8304 8415 8373 8443 8561 8627 8594 8423 8810 9040 9032 9140 9024 9287 9352 9393 9451 9447

Agreement index

Outlier analysis Prior

Posterior

79.6 5.2

5 5

23 86

95.2 33.7 107.2 102.3 103.3 104.8 106.5 104.6 101.4 105 106 76.8

5 5 5 5 5 5 5 5 5 5 5 5

3 37 2 3 3 3 3 3 3 3 4 9

5.7 107.6

5 5

100 2


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8

stratigraphic horizons represented at the site and the external correlation between the shell midden formation and the coastal evolution. Phase 1 (Level IV) dates to the start of the shell midden and predates the funerary activity at the site. Our Bayesian phase model indicates the start (10212e9443 cal BP at CI: 95.4%) and end (9727e9375 cal BP) boundaries for the formation time of Level IV, even though this estimation is based in just one valid radiocarbon determination for this phase. We acknowledge new radiocarbon dates from Level IV would be highly desirable for future improvements of the phase model. The date Beta-323495, elaborated on a sample of C. glaucum, indicates the first human occupations clearly associated to the formation of the shell midden are dated 9800e9454 cal BP, falling into the Early Holocene during the Boreal chrono-zone. Such a chronology does not agree with the Microblade Epipaleolithic chrono-cultural attribution suggested by presence of backed bladelets (Aparicio, 2008, 2014). Rather, the calibrated age of Level IV would be better correlated with the Early Mesolithic (ca. 10.1e8.7 ka cal BP), according to the Iberian Mediterranean archaeological sequence (Aura et al., 2011). The mismatch between the radiocarbon and the typology of the lithic assemblages could be explained if we consider that Level IV could have been composed by materials from different chrono-cultural

Therefore, the individual and model agreement indices as well as the convergence and phase indices indicate the robustness of the proposed three phase model regarding the radiocarbon data. 4. Discussion 4.1. Shell midden formation, radiocarbon phases and regional chrono-cultural sequence Our radiocarbon results suggest that shell midden formation took place from the bottom (Level IV) to the top of the archaeological stratigraphy (Level I, Layer C-1), spanning from 1106 to 1443 calendar years at a confidence interval of 68.2% and 1022e1965 calendar years at a confidence interval of 95.4%. The model queries about the occupation time within each phase based on the difference between the start and end boundaries (Interval) are also detailed in Table 7. It should be noted, the uncertainties of the Interval ranges considered for phases 1 (0e648, CI: 95.4%) and 3, (0e381, CI: 95.4%) which are result of the low number of consistent radiocarbon determinations for both phases. Future contributions should improve the current model by increasing the number of radiocarbon determinations associated to the bottom and the top of the stratigraphic sequence.

Table 6 Results of the El Collado site phase model (Model Agreement Index ¼ 103%) with the posterior (modelled) radiocarbon distributions. The three radiocarbon dates considered as outliers display an Individual Agreement Index of P ¼ 0. Phase

Phase 3

Phase 2

Phase 1

Sample ID

Provenience

Boundary UBA-27478 Beta-337186 Boundary Boundary 1626.1.1 Beta-337187 1625.1.1 1627.1.1 1622.1.1 1628.1.1 1619.1.1 1623.1.1 UBA-27477 1624.1.1 1620.1.1 1621.1.1 Boundary Boundary UBA-27479 Beta-323495 Boundary

End of Level I deposition C-1 C-1 Beginning of Level I deposition End of Level II deposition Burial 11 Layer II B Burial 9 Burial 12 Burial 5 Burial 13 Burial 1 Burial 6 Layer C-4 Burial 7 Burial 3 Burial 4 Beginning of Level II deposition End of Level IV deposition Level IV Level IV Beginning of Level IV

14

C BP age

7660 ± 44 7820 ± 30

7742 7610 7801 7900 7992 7976 8067 8166 8292 8319 8388 8491

± ± ± ± ± ± ± ± ± ± ± ±

35 30 38 32 34 33 37 35 57 35 30 37

7939 ± 44 9020 ± 40

Modelled 68% range cal BP

Modelled 95.4% range cal BP

8446 8628 8472 8510 8544 8419 8585 8701 8860 8758 8578 9078 9398 9257 9390 9443 9489 9611 8970 9665 9780

8499 8482 8682 8509 8535 8568 8449 8596 8847 8972 8950 8621 9123 9435 9309 9402 9465 9562 9728 8983 9800 10199

8398 8562 8412 8446 8488 8387 8514 8598 8640 8632 8501 8995 9142 9135 9247 9306 9359 9447 8650 9505 9517

Agreement index

8060 8378 8541 8391 8418 8444 8372 8464 8585 8630 8596 8457 8984 9094 9035 9142 9294 9312 9375 8637 9454 9443

110.5 P¼0

88.1 P¼0 106.6 100.1 101 102.6 107.5 102.1 100.7 102.8 105.2 81.6

P¼0 103.5

Table 7 Span and Interval queries from the El Collado site phase model. Query

Provenience

Modelled 68% cal. Years

Modelled 95% cal. Years

Span Interval Interval Interval

All sequence Level I occupation Level II occupation Level IV occupation

1106e1443 0e98 879e1023 0e193

1022e1965 0e381 817e1100 0e648

Overall, the modelled ages, phase intervals and entire sequence span advocate for a shorter chronological duration of the human occupations at the site than the 3500 years initially estimated from the lithic typology (Aparicio, 2014). The modelled chronology has further implications for the chrono-cultural interpretation of the

horizons accumulated at the bottom of the El Collado stratigraphic sequence. Supporting this hypothesis, we should bear in mind that the reduced set of backed bladelets recovered from Level IV was spatially restricted to the excavation unit G-III and it was found at the end of the second fieldwork season.


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9

Fig. 4. Multiplot of the Bayesian phase model of the El Collado site. The model structure is composed by three phases nested within the overall site sequence. Prior distributions (unmodelled calibrations) are shown in outline and posterior distributions (modelled) are solid.

Phase 2 consists of evidence of both burial activity and occupation during which shells and other food remains were incorporated into the matrix deposit of Level II. The modelled span estimates a duration of the radiocarbon activity associated with this level between 779 and 895 calendar years (CI: 95.4%). The chronology of Level II extends up the Boreal and partially covers the beginning of the Atlantic chrono-zones. Such a chronology is consistent with the Early Mesolithic cultural affiliation of the lithic assemblages, also known as Notch and Denticulated Mesolithic in Iberian terminology (Alday, 2006). Interestingly, this phase covers most of the occupational history of the El Collado site. Our study provides conclusive radiocarbon evidence of the contemporaneity between human occupations and the mortuary practices. First, the date UBA-27477 (on Bos primigenius) is statistically similar to that of Burial 7 (X2-Test: df ¼ 1 T ¼ 0.2 p < 0.05). In addition, two dates made on Cervus elaphus, considered as model outliers, provide statistically similar ages to five of the ten burials documented. This is the case for the date Beta-337186, which clearly overlaps with the radiocarbon ages of burials 9 and 11, and the date UBA-27479, statistically similar to those obtained from burials 5, 12 and 13. Phase 3 (Level I) covers the top of the archaeological stratigraphy. Our Bayesian phase model estimates 8509e8391 cal BP chronology for the beginning and 8499e8060 cal BP for the end of Level I deposition. The chronology of Level I is integrally developed during the Atlantic chrono-zone. The age of the date UBA-27478

(7660 ± 44 BP, 8482e8378 cal BP) fits well with the Late Mesolithic cultural attribution of the published lithic assemblages, with a microlithic component exclusively composed of trapezoidal armatures. Regionally, the Late Mesolithic of trapezes is radiometrically placed in the 8540e8010 cal BP range (95.4%) (Martí et al., 2009). In addition to the date UBA-27478 (7660 ± 44 BP, 8482e8378 cal BP), which is consistently associated with Level I, there is another radiocarbon determination (Beta-337187, 7610 ± 30 BP, 8449e8372 cal BP) that was identified as an outlier by the model in the Level II. Both dates (Beta-337187 and UBA-27478) fall within the chronological range of the Late Mesolithic. The available radiocarbon dates might suggest the lack of Mesolithic occupations postdating the chronology of the 8.2 ka cal BP event. This interpretation is consistently supported by the published lithic assemblages, which have not yielded any evidence of “Cocina Type” triangles, a highly diagnostic Final Mesolithic microlith. The current archaeological record lacks terminal Mesolithic (c. 8000e7600 cal BP) occupational evidence within a radius of 50 km around El Collado site, covering the adjacent areas such as the Serpis and Gorgos river valleys and the north-eastern
pez de Pablo mountain ranges of Alicante Province (Fern
andez-Lo et al., 2013). The closest Final Mesolithic sites are located approxi
Valley (Ferna
ndezmately 70 km inland in the Upper Vinalopo
pez de Pablo et al., 2013) and in Cueva de la Cocina in the UpLo per Júcar Valley (Juan Cabanilles and García Puchol, 2011).


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pez de Pablo, J., The timing of postglacial coastal adaptations in Eastern Iberia: A Bayesian Please cite this article in press as: Ferna chronological model for the El Collado shell midden (Oliva, Valencia, Spain), Quaternary International (2015), http://dx.doi.org/10.1016/ j.quaint.2015.10.077

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Fig. 5. Multiplot showing the correlation between the El Collado radiocarbon chronology (expressed as phase constrained as start and end distributions), the north hemisphere temperature evolution from the GRIP (Rasmussen et al., 2014) and the regional sea level changes (Albarracín et al., 2014).

4.2. Human occupation vs. coastal evolution In this section, we aim to establish a tentative correlation between the modelled radiocarbon chronology of the Early and Middle Holocene human occupations recorded at the El Collado site and the coastal evolution at both local and regional scales. At the top, Fig. 5 represents the start and end limits of each modelled phase. This graph is an output of the Bayesian phase model represented in Fig. 4. It is important to remember that the Oxcal Sum () function produces summed distributions of the dates within each phase, and the plotted summed probabilities are therefore contingent to the model constraints. At the centre, we have plotted a scaled version of the regional relative sea level curve for the Gulf of Valencia (Albarracín et al., 2014). This figure provides a relative overview of the regional eustatic changes documented between the Late Glacial and Middle Holocene. This curve does not consider modifications produced by neo-tectonics, however, which can be highly variable depending on local conditions. Finally, as a proxy of the northern hemisphere variability in temperatures, we represent a 20 yr mean curve of the d18O from the integration of the Greenland ice cores NGRIP, GRIP and GISP2 (Rasmussen et al., 2014). In addition, we have highlighted the revised onsets of two Early Holocene cold climate events 9.3 ka and 8.2 ka e produced in the framework of the INTIMATE project. The visual inspection suggests that the El Collado shell midden was formed along a period of dramatic eustatic changes, when the regional relative sea level rose from 40 m to 10 m. Local data from the Pego-Oliva marsh dates the maximum extent of the marine transgression between 8300 ± 170 BP (UBAR-78, ~ als and 7598e8762 cal BP, CI: 95.4%) and 6130 ± 100 BP (Vin Fumanal, 1995; Mateu et al., 1997). During the Flandrian transgression, locally dated at 6130 ± 100 BP, the sea level rose þ2 m from its current position and the coastline moved approximately ~ als and Fumanal, 1995). The impact produced by 3 km inwards (Vin

these middle Holocene eustatic changes on the existing coastal plain and associated lagoon ecosystems depended on the distance of the Mesozoic reliefs and adjacent glacis and alluvial fans from the coast line. From the immediate surroundings of the El Collado site northwards, the sea practically reached the foothills and eroded previous Pleistocene fans and cones, producing a micro-cliff ~ als sea coastline between the current cities of Oliva and Gandía (Vin and Fumanal, 1995:127). In contrast, from the El Collado site southwards, the relocation of the beach barriers inwards would have produced a reduction in the extent of the swamps, coastal lagoon areas and adjacent coastal plains. In our tentative correlation, we represent two global cold climate events within the chronological interval defined by the phases' start and end dates. The first is the 9.3 ka cold climate event (c. 9350e9240 cal BP), which falls at the beginning of El Collado phase 2 and partially overlaps with the modelled chronology of the first Mesolithic burials (burials 3 and 4). The second is the 8.2 ka cold climate event (ca. 8300e8140 cal BP), which is chronologically correlated with the end of the phase 3. As noted previously, the lithic assemblages suggest the presence of Late Mesolithic industries during phase 3 and the lack of Final Mesolithic geometric microliths dated from the 8000 cal BP onwards. Until new stratigraphic and chronological studies from the El Collado archaeological deposit be available providing evidence of today undetected Final Mesolithic occupations (since post-depositional disturbance, taphonomic or sampling biases cannot be ruled out completely), the chrono-stratigraphic data we present is consistent with the hypothesis that the site was abandoned during or soon after the 8.2 ka cold climate event. We do not know the effects of the 8.2 ka cold climate event on the coastal evolution of the southern sector of the Gulf of Valencia or the Pego-Oliva marsh, in part because of the lack of fine-grained chronological resolution in the dated sedimentary sequences. Different studies conducted in the Western Mediterranean continental shelf, however, have addressed the eustatic consequences of


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pez de Pablo, J., The timing of postglacial coastal adaptations in Eastern Iberia: A Bayesian Please cite this article in press as: Ferna chronological model for the El Collado shell midden (Oliva, Valencia, Spain), Quaternary International (2015), http://dx.doi.org/10.1016/ j.quaint.2015.10.077


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this climate event. For instance, in the Gulf of Lyon, the 8.2 ka cold climate event has been interpreted as a short stand-by interval that interrupted the process of marine transgression that followed the Last Glacial Maximum (Rabineau et al., 2005). Similar instances have been proposed in the continental shelf of southern Alicante province between the localities of Altea and Santa Pola, where high resolution seismic profiles have identified a prism at a 20 m depth related to the 8.2 ka cold climate event (Tent-Manclús et al., 2009). Considering that in the Eastern Iberian Peninsula, the 8.2 ka cold event is associated with more arid conditions, dry northerly winds
n (Frigola et al., 2007) and a negative hydrological balance (Morello
lez-Sampe
riz et al., 2009) than during the Early et al., 2007; Gonza Holocene, we hypothesise that coastal lagoon ecosystems around the El Collado site could have been affected. The extent of such an impact should be addressed in future sedimentary and palaeoecological studies on both the coastal lagoon records and the continental shelf. 5. Conclusion This study reports the first chronological analysis of El Collado stratigraphy, integrating previous AMS radiocarbon determinations of human samples with new AMS radiocarbon dates of short-lived events from undated stratigraphic horizons. The 16 AMS radiocarbon determinations considered here conform a representative sample of the human occupation at the El Collado site, allowing a tentative reconstruction of the chrono-stratigraphy. The vertical distribution of the radiocarbon dates makes evident some inversions in trench 1 caused by the repeated digging of pit graves and the agricultural disturbance; however, when the problematic determinations are identified as outliers, the remaining radiocarbon dates are grouped according to the major stratigraphic divisions and the calibrated distributions model is constrained, the resulting Bayesian phase model has a high agreement index (Amodel ¼ 103). Future contributions could be developed to improve the current chronological model, especially by incorporating new radiocarbon determinations from levels IV and I. The correlation among the modelled phases regarding the regional archaeological sequence and coastal evolution allow us to propose the following conclusions: 1) The shell midden formation took place from the bottom of the sequence, spanning 1022e1965 calendar years (CI: 95.4%). During this time, the southern sector of the Valencian Gulf witnessed major eustatic changes with a significant rise in the sea level and the inland relocation of the coastline. 2) The earliest radiocarbon dated occupations documented during phase 1 (Level IV) correspond the Early Holocene (9828e9551 cal BP). There is no funerary activity associated with this phase. 3) Phase 2 (Level II) encompasses radiocarbon evidence of both burial and occupational activities deposited between 9562 and 9312 cal BP, for the start boundary and 8535 to 8418 cal BP, for the end boundary, spanning 817e1100 years (CI: 95.4%) according to the Interval () command. 4) Phase 3 (Level I) records Late Mesolithic occupations that were deposited between 8509 and 8391 cal BP for the start boundary and 8499e8060 cal BP for the end boundary (CI:95.4%). There is no individual radiocarbon dates Final Mesolithic microliths post-dating the 8.2 ka cal BP climatic event. Acknowledgements We would like to thank to two anonymous reviewers for their constructive comments and suggestions. We gratefully

11


Aparicio (Diputacio
n Provincial de Valencia) acknowledge to Jose for letting us access to the malacological and faunal assemblages collections of the El Collado site. We also thank to Alfred Sanchís and Carmen Tormo for their assistance in the taxonomic identifi
mez-Puche for her cation of the dated samples and to Magdalena Go helpful comments on previous versions of the manuscript. The present study was conducted in the context of the project POSTGLACIAL-MED funded by the MINECO Spanish Ministry (Ref. HAR2013-41197). The author is supported by the MINECO
n y Cajal postdoctoral research grant Spanish Ministry dRamo (Ref. RYC-2011-09363).

References Alday, A., 2006. El mesolítico de muescas y denticulados en la cuenca del Ebro y el

neo peninsular. Diputacio
n Foral de Alava, litoral mediterra Departamento de Cultura.
ntara-Carrio
, J., Montoya-Montes, I., Font
Albarracín, S., Alca an-Bouzas, A., Somoza, L., Amos, C.L., Rey Salgado, J., 2014. Relict sand waves in the continental shelf of the Gulf of Valencia (Western Mediterranean). Journal of Sea Research 93, 33e46.
neo Occidental. Serie de Aparicio, J., 1979. El Mesolítico en Valencia y en el Mediterra
n Provincial de Valencia. Trabajos Varios del SIP, nº59. Diputacio Aparicio, J., 1992. Los orígenes de Oliva. Real Academia de Cultura Valenciana,
rica nº 9. Valencia, pp. 75e143. Serie histo
polis mesolítica de El Collado (Oliva-Valencia). Varia VIII. Aparicio, J., 2008. La necro
n provincial de Valencia. Diputacio Aparicio, J., 2014. El Collado (Oliva-Valencia). In: Sala, R. (Ed.), Pleistocene and Holocene Hunter Gatherers in Iberia and the Gibraltar Strait: the Current
n Atapuerca, Archaeological Record. Universidad de Burgos. Fundacio pp. 338e344.
n, Y., García, O., Jardo
n, P., Jorda
, J.F., Molina, Ll, Morales Pe
rez, J.V., Aura, J.E., Carrio
rez, G., Pe
rez, M., Rodrigo, M.J., Verdasco, C., 2006. EpipaleolíticoPascual, J.Ll, Pe Mesolítico en las comarcas centro-meridionales valencianas. In: Alday, A. (Ed.), El mesolítico de muescas y denticulados en la cuenca del Ebro y el litoral

neo peninsular. Diputacio
n Foral de Alava. mediterra Departamento de Cultura,
Alava, pp. 65e120.
, J., Montes, L., Utrilla, P., 2011. Human responses to Younger Dryas in Aura, J.E., Jorda the Ebro valley and Mediterranean watershed (Eastern Spain). Quaternary International 242 (2), 348e359.
rez, M., Badal, E., Tiffagom, M., Morales, J.V., Avezuela, B., Aura, J.E., Jord
a, J.F., Pe 2013. Concheros del sur de Iberia en el límite Pleistoceno-Holoceno. In: de la
rez, F. (Eds.), Universitatis Ovetensis Magister. Rasilla, M., Javier Fortea Pe
nsula. Universidad de Oviedo, pp. 179e194. Editorial Me Aura, J.E., Marlasca, R., Rodrigo, M.J., Jord
a, J.F., Salazar-García, D.C., Morales, J.V., 2015. Llises, orades i alguna anguila. L'Ictiofauna mesolítica de les Coves de Santa Maira (Castell de Castells, La Marina Alta, Alacant). In: Preses petites i ria grups humans en el passat. II Jornades d'arqueozoologia. Museu de Prehisto ncia, pp. 121e138. de Vale Bicho, N., Cascalheira, J., Marreiros, J., Gonçalves, C., 2013. Chronology of the Mesolithic occupation of the Muge valley, central Portugal: the case of Cabeço da Amoreira. Quaternary International 308e309, 130e139.
poca paleolítica en Oliva (Valencia). Boletín de la Bosc a, E., 1916. Un paradero de la e Real Sociedad de Historia Natural XVI, pp. 81e83. Brown, T.A., Nelson, D.E., Vogel, J.S., Southon, J.R., 1988. Improved collagen extraction by modified Longin method. Radiocarbon 30, 171e177. Bronk Ramsey, C., 2011. OxCal v.4.1 Manual. https://c14.arch.ox.ac.uk/oxcal/OxCal. html (accessed on-line 20.01.15.). Bronk Ramsey, C., 2009a. Bayesian analysis of radiocarbon dates. Radiocarbon 51 (1), 337e360. Bronk Ramsey, C., 2009b. Dealing with outliers and offsets in radiocarbon dating. Radiocarbon 51 (3), 1023e1045. Bronk Ramsey, C., Higham, T., Bowles, A., Hedges, R., 2004. Improvements to the pretreatment of bone at Oxford. Radiocarbon 46, 155e163. Bronk Ramsey, C., Dee, M., Lee, S., Nakagawa, T., Staff, R., 2010. Developments in the calibration and modelling of radiocarbon dates. Radiocarbon 52 (3), 953e961. Buck, C.E., Cavanagh, W.G., Litton, C.D., 1996. Bayesian Approach to Interpreting Archaeological Data. Wiley, Chichester. Colonese, A.C., Mannino, M.A., Bar-Yosef Mayer, D.E., Fa, D.A., Finlayson, J.C., Lubell, D., Stiner, M.C., 2011. Marine mollusc exploitation in Mediterranean prehistory: an overview. Quaternary International 239 (1e2), 86e103. Fernandez-Lopez de Pablo, J., Salazar, D., Subira, M.E., Roca, C., Gomez, M., Richards, M.P., Esquembre, M.A., 2013. Late Mesolithic burials at Casa Corona (Villena, Spain): direct radiocarbon and palaeodietary evidence of the last forager populations in Eastern Iberia. Journal of Archaeological Science 40, 671e680. Frigola, J., Moreno, A., Cacho, I., Canals, M., Sierro, F.J., Flores, J.A., Grimalt, J.O., Hodell, D.A., Curtis, J.H., 2007. Holocene climate variability in the western Mediterranean region from a deepwater sediment record. Paleoceanography 22, PA2209,. http://dx.doi.org/10.1029/2006PA001307.


ndez-Lo
pez de Pablo, J., The timing of postglacial coastal adaptations in Eastern Iberia: A Bayesian Please cite this article in press as: Ferna chronological model for the El Collado shell midden (Oliva, Valencia, Spain), Quaternary International (2015), http://dx.doi.org/10.1016/ j.quaint.2015.10.077


ndez-Lo
pez de Pablo / Quaternary International xxx (2015) 1e12 J. Ferna

12


, E., Subir García-Guixe a, M.E., Richards, M.P., 2006. Paleodiets of humans and fauna from the Spanish Mesolithic site of El Collado. Current Anthropology 47 (3), 549e556. lia Subira , M.E., Terradas, X., Santos, F.J., Agullo
, L., Go
mezGibaja, J.F., Eula se, F., Ferna
ndez-Lo
pez de Pablo, J., 2015. The Emergence of Martínez, I., Allie mesolithic Cemeteries in SW Europe: insights from the El Collado (Oliva, Valencia, Spain) radiocarbon record. Plos One 10 (1), 1e18.
lez-Sampe
riz, P., Utrilla, P., Mazo, C., Valero-Garce
s, B., Sopena, M.C., Gonza
n, M., Sebastia
n, M., Moreno, A., Martínez, M., 2009. Patterns of human Morello occupation during the Early Holocene in the Central Ebro Basin (NE Spain) in response to the 8200-yr climatic event. Quaternary Research 71, 121e132. Ivell, R., 1979. The biology and ecology of brackish lagoon bivalve, Cerastoderma  re, in Lago Pungo, Italy. Journal of Molluscan Studies 45, glaucum Bruguie 364e382. Jord
a, J.F., Avezuela, B., Aura, J.E., Martín-Escorza, C., 2011. The gastropod fauna of the Epipalaeolithic shell midden in the Vestibulo chamber of Nerja Cave (M
alaga, southern Spain). Quaternary International 244 (1), 27e36.
dans la Juan-Cabanilles, J., García Puchol, O., 2011. Rupture et continuite
olithisation du versant me
diterrane
en de la pe
ninsule Ibe
rique: mise  ne a
preuve du mode le de dualite
culturelle. In: Perrin, T., Manen, Cl, l'e Marchand, G., Allard, P., Binder, D., Illet, M. (Eds.), Transition, ruptures et con
durant la pre
histoire transitions, rupture, and continuity in prehistory, tinuite
te
pre
historique française. Ministe re de la Culture et de la Session H. Socie
partement de la Dordogne, pp. 405e417. Communication. De Kennet, D.J., Culleton, B., 2010. A bayesian chronological framework for determining site seasonality and contemporaneity. In: Reitz, E., Quitmyer, I., Hurst, D. (Eds.), Seasonality and Human Mobility along the Georgia Bight, Anthropological Papers of the American Museum of Natural History 97, pp. 38e49.
pez de Pablo, J., Martí, B., Aura, J.E., Juan Cabanilles, J.J., García, O., Fern
andez-Lo 2009. El Mesolitico geometrico de tipo “Cocina” en el Pais Valenciano. In: Utrilla, P., Montes, L. (Eds.), El Mesolitico Geometrico en la Peninsula Iberica, Monografias Arqueologicas no 45. Universidad de Zaragoza, pp. 205e258. ~ als, M.J., Moreiro, M., 1997. Biofacies marginolitorales del MediMateu, G., Vin
neo Occidental (Baleares, Valencia, Alicante y Murcia). In: Bolleti de la terra  ria Natural Balears 40, pp. 123e134. Societat d'Histo Millard, A.R., 2014. Conventions for reporting radiocarbon determinations. Radiocarbon 56 (2), 555e559.
n, M., Valero, B., Moreno, A., Gonz
Morello alez, P., Mata, P., Romero, O., Maestro, M., Navas, A., 2007. Holocene palaeohydrology and climate variability in northeastern Spain: the sedimentary record of Lake Estanya (Pre-Pyrenean range). Quaternary International 181, 15e31. Mulazzani, S., 2013. Le Capsien de Hergla (Tunisie): Culture, environnement et
conomie. Africa Magna Verlag, Frankfurt am Main. e Rabineau, M., Berne, S., Aslanian, D., Olivet, J.-L., Joseph, P., Guillocheau, F., Bourillet, J.-F., Ledrezen, E., Granjeon, D., 2005. Sedimentary sequences in the

́ ́

́ ́

́

́ ́

́

Gulf of Lion: a record of 100,000 years climatic cycles. Marine and Petroleum Geology 22, 775e804. Rasmussen, S.O., Bigler, M., Blockley, M.S., Blunier, T., Buchardt, S.L., Clausen, H.B., Cvijanovic, I., Dahl-Jensen, D., Johnsen, S.J., Fischer, H., Gkinis, V., Guillevic, M., Hoek, W.Z., Lowe, J.J., Pedro, J.B., Popp, T., Seierstad, I.K., Steffensen, J.P., Svensson, A.M., Vallelonga, P., Vinther, B.M., Walker, M.J.C., Wheatley, J.J., Winstrup, M., 2014. A stratigraphic framework for abrupt climatic changes during the Last Glacial period based on three synchronized Greenland ice-core records: refining and extending the INTIMATE event stratigraphy. Quaternary Science Reviews 106, 14e28. Reimer, P., Hoper, S., McDonald, J., Reimer, R., Svyatko, S., Thompson, M., 2015. The Queen's University, Belfast Laboratory Protocols Used for AMS Radiocarbon Dating at the 14CHONO Centre. In: Scientific Dating Report. Research Report Series 5e2015. English Heritage. Reimer, P.J., Bard, E., Bayliss, A., Beck, J.W., Blacwell, P.G., Bronk Ramsey, Ch,
, C., Heaton, Th, Grootes, P.M., Guilderson, T.P., Haflidason, H., Hajdas, I., Hatte Hoffmann, D.L., Hogg, A.G., Hughen, K.H., Kaiser, F.K., Kromer, B., Manning, S., Niu, M., Reimer, R.W., Richards, D.E., Scott, E.M., Southon, J.R., Staff, R.A., Turney, ChS.M., Van der Plicht, J., 2013. INTCAL 13 and MARINE 13 Radiocarbon age calibration curves 0-50,000 years Cal BP. Radiocarbon 55 (4), 1869e1887. Reimer, P.J., McComac, F.G., 2002. Marine radiocarbon reservoir corrections for the Mediterranean and Aegean Seas. Radiocarbon 44 (1), 159e166. Reimer, P.J., Reimer, R.W., 2001. A marine reservoir correction database and on-line interface. Radiocarbon 43 (2), 461e463. Rey, J., Fumanal, M.P., 1996. The Valencian coast (western Mediterranean): neotectonics and geomorphology. Quaternary Science Reviews 15, 789e802.
rat, N., Bassinot, F., Siani, G., Paterne, M., Arnold, M., Bard, E., Maitivier, B., Tisne 2000. Radiocarbon reservoir ages in the Mediterranean Sea and Blck Sea. Radiocarbon 42/2, 271e280.
vez, A., Soria, J.M., Benabdeolued, N.Y.B., Corbí, H., Rey, J., Tent-Manclús, J.E., Este
benes, A., 2009. Registro del evento 8.2 en la plataforma continental Pina, J.A., Ye ~ a). Geogaceta 47, 97e100. de Alicante (SE, Espan Thakar, H., 2014. Sites forlorn: dating intervals of abandonment at three shell middenson Santa Cruz Island, California using Bayesian chronological models. Journal of Archaeological Science 52, 633e644. Van Klinken, G.J., 1999. Bone collagen quality indicators for palaeodietary and radiocarbon measurements. Journal of Archaeological Science 26, 687e695. ~ als, M.J.M.P., Fumanal, M.P., 1995. Quaternary development and evolution of the Vin sedimentary environments in the central mediterranean spanish coast. Quaternary international 30, 119e128. Wicks, K., Mithen, S., 2014. The impact of the abrupt 8.2 ka cold event on the Mesolithic population of western Scotland: a Bayesian chronological analysis using activity events as a population proxy. Journal of Archaeological Science 45, 240e269.

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ndez-Lo
pez de Pablo, J., The timing of postglacial coastal adaptations in Eastern Iberia: A Bayesian Please cite this article in press as: Ferna chronological model for the El Collado shell midden (Oliva, Valencia, Spain), Quaternary International (2015), http://dx.doi.org/10.1016/ j.quaint.2015.10.077