Architectural Sequence and Charcoal Sampling

The present study has focused on the four monuments in Los Llanetes, the eastern cluster in the El Pozuelo megalithic complex. They are located in the valley; distributed in pairs of monuments and creating an area reserved for the realm of the dead, within a megalithic landscape that includes the settlement on Chinflón Hill, the copper mines and the natural surrounding formations (Figure 1b). Dolmens 1 and 2 occupy two different mounds connecting by gentle slopes, while Dolmens 3 and 4 are on a flat promontory (Figure 1c). They were excavated in 1946, giving rise to the study of the architectures and grave goods (Cerdán et al. Reference Cerdán, Leisner and Leisner1952).

The documentation and materials used for the present study come from two archaeological fieldwork projects in 2009–2010 and 2012–2014. This work employed a methodology that included extensive excavation of areas, a full architectural study of internal spaces and the selective micro-spatial exploration of outer areas: the mounds, front access zone and the surrounding areas. The stratigraphic record has not been exhausted in any of the excavated sectors, leaving sections for future research. This working method has succeeded in reconstructing the stratigraphic-structural sequence of the remains and their position in a relative chronology; and it has identified the structural phases, the stages of activity and materials associated with them.

Research in the Los Llanetes cluster enabled an interpretation of the stratigraphy, architecture and diachronic sequence that is more complex archaeologically than was traditionally thought (Linares-Catela Reference Linares-Catela2017). Three elements can be emphasized:

• The final form of the monuments is the result of the concatenation of a series of architectural projects. In each of these, different models of dolmens were superimposed, with a tendency from simpler to more complex monuments (Figure 2). Each model displays particular characteristics and was constructed with different purposes and intentions.

  

  Figure 2 Architectural sequence of the Los Llanetes cluster, El Pozuelo complex. Evolution of the monuments.

• The existence of “megalithic operational chains” associated with each primary building project or reform. The work was characterized by the sophistication, specialization, and continuity of a technical tradition, seen in the selection of materials, treatment and building systems (Linares-Catela Reference Linares-Catela and Ard2021).

• The long and complex duration of the cluster, with materials characterising different chrono-cultural phases in Later Prehistory, from the Late Neolithic to the Bronze Age, and various historical periods.

Nonetheless, each dolmen displays particular stratigraphies, an architectural biography and specific activity in Later Prehistory.

Dolmen 1 is a mound containing two parallel chambers with independent accesses (Figure 3). They clearly differ in their shape, size and heights. The circular mound is delimited by a ring of kerbstones. On the outside, a circular stone platform and two stepped levels of terraces are delimited by drystone walls that form a monumental enclosure that is more recent than the dolmen (Figure 3a). The archaeological study determined a stratigraphic-structural sequence (Figure 3b) with the following phases:

Figure 3 El Pozuelo 1: (a) photogrammetric survey; (b) plan with architectural phases, stratigraphic-structural sequence and location of ¹⁴C samples.

• Phase 1: dolmen with an elongated oval chamber oriented to the SE (117º). It corresponds to half the structure of the north chamber, from its middle to the head. It is 3.75 m long, with a maximum width in the middle of 2.05 m and a height of up to 1.80 m. It is formed by large orthostats, the first of which rests on the headstone while the others are vertical. The floor is on the bedrock which was lowered with a slope down from the access, with a stele pit in the middle, aligned with the axis of the chamber. It is inside a circular mound 9 m in diameter.

• Phase 2: a dolmen with an elongated chamber that was formed by adding two curving walls of stones to prolong the original axis of symmetry. It reaches a length of 7 m. The axial stele was placed in the access section. The oval mound, with a kerb, reached 12.50 m in length on its long axis.

• Phase 3: dolmen with double parallel chambers and independent entrances. Two sub-phases can be differentiated. In Phase 3A, the work involved removing the southern half of the pre-existing mound, building the south chamber and its access vestibule, moving several stones, paving the north chamber with clay, and rebuilding the mound. This created a circular mound 12.60 m in diameter delimited by kerbstones. The south chamber, which was lower and built with smaller stones than the contiguous one, is curved and 6.50 m long. It has two headstones.

  In Phase 3B, the frontal façade was transformed and repairs were made to the south chamber. The work enlarging the mound formed an atrium with an open monumental façade including two access vestibules oriented generally towards the east (90°). The north wall of the south chamber was repaired by moving the orthostats and the entrance of the north chamber was transformed by removing the first two stones and replacing the axial stele.

• Phase 4: the outer area was monumentalized. The surrounding terrace and structures in the north and front were built.

• Phase 5: the outer frontal area was monumentalized by laying a pavement, several altars, circular structures and steles, with which ritual hearths in the atrium are associated.

• Phase 6: funerary reuse.

• Phase 7: the dolmen was partially dismantled and the area of terraces with a circular platform was built, which implied breaking and removing the capstones, orthostats and steles and digging out the mound for their reuse. The monumental enclosure includes two types of structures. First, a drystone wall platform 23.50 m by 20.50 m in size that surrounded the dolmen, between 0.50 and 1.0m high, which contained large stones and slabs from the dolmen. It had several accesses; one on the north-east side, segmented by an orthostat reused as a standing-stone, and a ramp on the west side. It was restructured and rebuilt on two occasions (Phases 7B and 7C). Second, two sub-quadrangular surrounding terraces were built lower down, delimited by drystone walls with the shape of an incline towards the outside.

• Phase 8: the terraced enclosure was abandoned.

• Phase 9: reuse in the Middle Bronze Age, when the mound of the dolmen was reshaped by partially emptying the north chamber, where a mining hammer with a central groove was found.

• Phase 10: reuse in the Late-Final Bronze Age, when a pit was dug in the mound.

• Phase 11: reuse in the Late Iron Age, as witnessed by the pit dug in the north chamber.

Dolmen 2 is a monument with double perpendicular chambers (Figure 4). Its circular mound is delimited by a prominent levelling platform and a ring of kerbstones with protruding oblique stones, created in four architectural projects (Figure 4a). The archaeological study (Figure 4b) has determined the following phases.

Figure 4 El Pozuelo 2: (a) photogrammetric survey; (b) plan with architectural phases, stratigraphic-structural sequence and location of ¹⁴C samples.

• Phase 1: dolmen with an elongated oval chamber. This is the west chamber formed by two walls and a headstone, on a northwest-southeast line. An old stele was reused with engravings on the extrados. It was 3.50 m long, with a maximum width of 1.70 m in the middle and a maximum height of 1.60 m. The floor was dug into the bedrock. The oval mound was 9.80 m long on its long axis.

• Phase 2: dolmen with an elongated chamber 5.25 m long. Its construction involved dismantling and partly rebuilding the north wall of the old chamber, as well as lengthening the structure and enlarging the mound by a metre on the eastern front, reaching up to 2 m in height. The chamber was rotated towards the east (90°), which was the axis of symmetry of the monument.

• Phase 3: dolmen with double perpendicular chambers. Its design involved partially digging out at least one orthostat and part of the old mound, as a hole was made for the south chamber. The mound and kerbstone ring were rebuilt next to the interior. The chamber, 3.30 m long, 1.50 m wide, and 1.40 m in maximum height, was oriented towards the north (10°). It was formed by a headstone and regular slender orthostats and was lower than the original one, with a floor of beaten clay over the bedrock. The elliptical mound was 12.75 m long on its axis of symmetry.

• Phase 4: the east front of the mound was enlarged by adding two sections of the ring and filling the mass of the mound, which reached 13.25 m in length.

• Phase 5: funerary reuse of the chambers.

• Phase 6: reuse of the space for a possible construction of a tholos-type structure in the eastern half. This meant the mound of the monument was reformed. The negative structure is characterized by a passage and the start of a circular chamber with slabs and stone walls, oriented towards the northeast (67°).

• Phase 7: the monument was partly dismantled, and the remains and materials were added to the surrounding ditch enclosure, which has only been delimited on the surface. The enclosure is elliptical, oriented on a northeast alignment (67°), formed by a discontinuous perimeter ditch dug in the substrate with an embankment towards the exterior. The ditch would have a U- or V-shaped cross-section, about 1.50 m wide and up to 0.80 m deep, delimiting an area of 36.50 m by 23 m. A “pincer-shaped” access in the northeast was flanked by a stele on each side. Another access would have been on the southwest side. On the inside there was a small perimeter ditch, and two groups of circular earthen structures were located on the outside.

• Phase 8: the monumental enclosure was abandoned.

Dolmen 3 is characterized by an internal structure formed by two parallel chambers 4.5 m in length connected by an antechamber and a converging passage (Figure 5), 2.60 m long. They were in a circular mound 16.50 m in diameter and up to 3.50 m high above the outer ground level, delimited by a ring of kerbstones with a circumference of 50 m. Engraved and painted steles were recycled in the antechamber (Figure 5a). The following building phases in Later Prehistory have been determined by the archaeological study (Figure 5c).

Figure 5 El Pozuelo 3–4: (a) aerial view of dolmen 3; (b) aerial view of dolmen 4; (c) plan with architectural phases, stratigraphic-structural sequence and location of ¹⁴C samples.

• Phase 1: dolmen with an elongated oval chamber, corresponding to the north chamber, 4.60 m long, 2.10 m wide, and up to 2 m high, with an axis of symmetry on 124° (southeast). It has a headstone, walls with vertical stones placed regularly and a floor excavated into the substrate. It would have had axial steles. The chamber was inside a circular mound 11 m in diameter.

• Phase 2: dolmen with an elongated chamber formed by adding a trapezoidal antechamber in the access, 1.65 m long and 1.60 m high. The mound was enlarged and reached about 13 m in diameter.

• Phase 3: Dolmen with parallel double chambers and converging passage. Its construction involved partially dismantling the old mound, adding the south chamber and rebuilding the antechamber, the access passage and the wedge-shaped vestibule. The axis of symmetry was rotated towards the east (90°), marked by the projection of the axial steles in the antechamber with a free-standing stele in the access. The south chamber is elbow-shaped, with two headstones and more slender stones in the walls which partly overlap in the curved section. The trapezoidal antechamber, 2.30 m long, contains seven recycled steles with engravings in the places of transition: stele in the frontal closure, two jambs in the axis of symmetry, one in the access and the other three in the walls. The mound was enlarged and reached its maximum circular form, with a stone pavement around it.

• Phase 4: transformation of the front façade and the access, including the partial reconstruction of the passage wall on a 110° alignment (southeast). This created a narrow access and an enlargement of the façade with vertical slabs.

• Phase 5: the front access was monumentalized, conditioning the position of two altars: a stone and clay altar attached to the atrium and another one carved in the rock.

• Phase 6: funerary reuse of the interior of the dolmen.

Dolmen 4 consists of a covered gallery in a circular mound on a levelled platform, 15.50 m in diameter and reaching 3.50 m in height above the exterior ground level (Figure 5b). The structure of orthostats 10.25 m in length is segmented into three areas: open passage, antechamber with a transversal stone, and an elongated oval chamber with central pillars. Its height varies from 1.30 m to 1.80 m. The floor was dug into the bedrock. The dolmen was entered down steps carved into the rock, with a stele on the left-hand side. The stratigraphic and structural study has revealed the following phases in its construction (Figure 5c).

• Phase 1: construction of an elongated oval chamber, 6.75 m long and up to 3.60 m wide, with 6 or 7 central pillars. These supports may have been recycled steles, which marked the axis of symmetry on 110° (southeast). The regular orthostats were placed vertically. The floor sloped down from the access to the headstone. The structure was in a circular mound, 12.50 m in diameter on a foundation of hard compacted clay.

• Phase 2: dolmen with an elongated chamber 7.75 m long. It was created by adding a quadrangular antechamber at the end by placing three orthostats on both sides of the walls and the transversal position of a recycled slab. This support, with side grooves for it to be fixed, was shortened so that it could be reused. The first pillar was replaced and rotated towards the east (90°), marking the new orientation of the axis of symmetry. The mound was enlarged, and made into an oval shape, with a length of 15 m on its long axis.

• Phase 3: covered gallery dolmen with an outer passage and façade with a stepped vestibule. The work involved lengthening the structure with three orthostats leaning at 30–45° on each side, with a rise from 0.90 to 1.40 m, reaching the full length of the structure. The mound was enlarged concentrically to reach its final size.

• Phase 4: the front façade was monumentalized and transformed. This involved placing the stones in the wedge-shaped vestibule and carving the access steps in the rock substrate.

• Phase 5: the external area was monumentalized with two actions. A stele was placed with a quadrangular altar at its foot, and a stone pavement was laid in the outer vestibule, while a stele-altar was associated with hearths in the front outer area.

• Phase 6: funerary reuse of the interior of the dolmen.

Phases 7–10 are the same in Dolmens 3 and 4, which were located in the same place. The following actions took place in each phase:

• Phase 7: partial dismantling to build the surrounding terraced enclosure, formed by three levels delimited by drystone walls and a ramp carved in the outcrop of rock on the southwest side. This project implied removing and breaking the capstones, orthostats, and pillars, as well as digging out the mound, etc.

• Phase 8: abandonment of the terraced enclosure.

• Phase 9: reuse in the Middle Bronze Age, both of the inner area without a cover and of the outer areas.

• Phase 10: reuse in the Late-Final Bronze Age, as evidenced by the find of miners’ hammers with a central groove, and a funerary pit with a stele and a pavement between Dolmens 3 and 4.

The radiocarbon dates for the four monuments were obtained from samples of charcoal. This is the only type of organic macro-remain conserved in the dolmens and found in most of the stratigraphic and architectural units. No bones could be dated because no fragments have been preserved owing the high acidity of the clay. These unfavourable physical-chemical conditions destroy the osseous remains, as observed at other sites in the western Sierra Morena (Nocete et al. Reference Nocete, Lizcano, Nieto, Sáez, Linares, Orihuela and Rodríguez2004). Therefore, in these dolmens, charcoal is the only organic material susceptible of being dated, as in the case of most sites in the Iberian Pyrite Belt and other southwestern regions, where highly acidic soils are common. As a result, during the excavation all the charcoal fragments were collected systematically when dry sieving the sediment from the stratigraphic units and hearths with concentrations of remains. In total, 644 charcoal remains were recorded, mostly from prehistoric contexts. The anthracological study succeeded in identifying each taxon and discriminated between the use of twigs and branches.

The presence of charcoal at megalithic sites may be due to different reasons and social practices, as wood was used in structures built during the construction of the monuments, to cremate individuals during the funerary activity, and in hearths and ritual fires (Zapata and Figuerial Reference Zapata, Figueiral and Buxó2003). Its preservation depends on various taphonomic factors. It is therefore essential to determine the combustion processes derived from human activity and the natural and/or anthropic post-depositional processes resulting in its presence at archaeological sites (Théry Parisot et al. Reference Théry Parisot, Chabal and Chrzavzez2010).

A strategy was followed for the selective sampling of charcoal from building units, constructions and levels that enable the chronology of the phases to be established. Priority was given to apparently unaltered archaeological contexts displaying clear stratigraphic relationships of superimposition, succession, horizontality and/or continuity within the architectural sequence. In this way, 70 samples were chosen to be dated. The selection of charred wood samples was based on four criteria:

1. 1. The presence and suitability to date levels of the constructions, other structures and the uses that mark the rhythm and diachronic development of the monuments.

2. 2. The degree of alteration caused by the successive reuses of the site.

3. 3. The preference for short-lived species, especially branches, in order to avoid the old-wood effect. Thus, fragments of bush branches (Rosaceae, Ericaceae, Olea, Arbustus sp.) were chosen in the case of charcoal dispersed in the sediment or present in the interior and exterior levels of the monuments, associated with either funerary or ritual activity. However, dates have also been obtained for long-life species (Quercus subgenus Quercus, Quercus ilex) in certain stratigraphic units or structures (pavements, ditches and foundation pits, postholes, and hearths) when short-lived charred wood samples were not available.

4. 4. Their suitability to define the temporality of the constructions or levels and to establish short-duration events connected with specific ritual practices, such as the hearths.

The archaeological contexts and the chronometric results allow the dates to be sorted into two large temporal groups. Thus, 27 dates correspond to Later Prehistory, from the Late Neolithic to the Iron Age. The other 43 dates are correlated with different historical reuses, from Antiquity to the Contemporary Age. The number of prehistoric dates per dolmen is unequal: 13 for Dolmen 1, two for Dolmen 2, six for Dolmen 3, five for Dolmen 4 and one for the outer area around Dolmens 3 and 4 (Table 1; Figures 3–5). Priority was given to the selection of samples from:

Table 1 Archaeological contexts of dated charcoal samples from the Los Llanetes cluster, El Pozuelo complex.

• Construction levels and elements (n=12), of two types: (a) permanent structures, such as the foundations of the mounds and walls (3), mounds (2), ditches or foundation pits (5) and pavements (1); and (b) ephemeral structures, such as postholes (1), associated with the timber used during the construction of the megaliths, like the structural framework, tripods, and trestles. The charcoals were found in the sedimentary fill and in the stratigraphic levels sealed after the construction activity, remaining buried in the case of the post holes of wooden structures and/or under the structures in the case of durable architectural elements of stone and clay: mounds, foundation ditches, sockets, and clay base levels. Therefore, even assuming that some charcoals may be older residual remains incorporated into the construction levels, the samples provide a terminus post quem for the building and/or reform events in the monuments and the chronometric results will be very close to the time of the construction or modification of the architecture. Furthermore, we have sufficient guarantees that it is not charcoal from later activities.

• Floors and sediments over floors (n=9), differentiating between activity levels in the chambers (2) and sediment formed on surfaces and internal transit areas (7). These are pieces of charcoal deposited in those levels during the different activities and funerary and ritual practices carried out in the dolmens. Again, these samples date specific events in the use of the structures.

• External structures (n=5), differentiating between a hearth (1), stele pit (1), sediments over pavements (2) and a terrace (1). The charcoals has been recorded in structures that were constructively backfilled (foundation pits), covered by sediment after use by natural and/anthropic processes (hearths) and deposited on the ground (pavements) as a result of fires or combustion practices carried out in the site. These samples can date particular activity phases, monumentalization processes and ritual practices carried out in the outer areas, sometimes of a short duration, as in the case of the hearths.

• Pit dug during the reuse of interior areas (n=1). The charcoal was buried in an intentional fill of the structure in Dolmen 1.

Bayesian Methods and Models

The radiocarbon dates were obtained from small charcoal fragments (less than 1 g in weight) analyzed in the Spanish National Accelerator Centre (CNA) in Seville. This laboratory follows rigorous protocols in the preparation, extraction of carbon dioxide by graphitization, treatment, and measurement of the samples by accelerator mass spectrometry (AMS) (Santos et al. Reference Santos, Gómez Martínez and García León2009, Reference Santos, Agulló, Diéguez and Gómez Martínez2015). All the samples provided a reliable radiocarbon age (Stuiver and Polach Reference Stuiver and Polach1977) with percentages of radiocarbon concentrations (pM) suitable for the calculation of the age BP. The δ13 values are provided by measuring the graphite by AMS. The BP ages were calibrated with the IntCal20 curve (Reimer et al. Reference Reimer, Austin, Bard, Bayliss, Blackwell, Bronk Ramsey, Butzin, Cheng, Edwards, Friedrich, Grootes, Guilderson, Hajdas, Heaton, Hogg, Hughen, Kromer, Manning, Muscheler, Palmer, Pearson, Van der Plicht, Reimer, Richards, Scott, Southon, Turney, Wacker, Adolphi, Büntgen, Capano, Fahrni, Fogtmann-Schulz, Friedrich, Köhler, Kudsk, Miyake, Olsen, Reinig, Sakamoto, Sookdeo and Talamo2020) using the OxCal 4.4 program (Bronk Ramsey Reference Bronk Ramsey2001, Reference Bronk Ramsey2009), using the ranges of dates with probabilities of 68.3% (1σ) and 95.4 % (2σ) for the calendar ages. Following Stuiver and Polach (Reference Stuiver and Polach1977), the dates have been rounded to the nearest 10 years, as the radiocarbon deviation is greater than 25 years in all the samples (Table 2; Figure 6). The presentation of the dates follows the recommendations of Millard (Reference Millard2014).

Table 2 Calibrated radiocarbon dating of the Los Llanetes cluster, El Pozuelo complex (OxCal v.4.4 Bronk Ramsey [Reference Bronk Ramsey2021]; r: 5 IntCal20 atmospheric data from Reimer et al. [Reference Reimer, Austin, Bard, Bayliss, Blackwell, Bronk Ramsey, Butzin, Cheng, Edwards, Friedrich, Grootes, Guilderson, Hajdas, Heaton, Hogg, Hughen, Kromer, Manning, Muscheler, Palmer, Pearson, Van der Plicht, Reimer, Richards, Scott, Southon, Turney, Wacker, Adolphi, Büntgen, Capano, Fahrni, Fogtmann-Schulz, Friedrich, Köhler, Kudsk, Miyake, Olsen, Reinig, Sakamoto, Sookdeo and Talamo2020]).

Figure 6 Calibrated radiocarbon dating of the Los Llanetes cluster: El Pozuelo 1–4 (OxCal v.4.4 Bronk Ramsey [Reference Bronk Ramsey2021]; r:5 IntCal20 atmospheric data from Reimer et al. [Reference Reimer, Austin, Bard, Bayliss, Blackwell, Bronk Ramsey, Butzin, Cheng, Edwards, Friedrich, Grootes, Guilderson, Hajdas, Heaton, Hogg, Hughen, Kromer, Manning, Muscheler, Palmer, Pearson, Van der Plicht, Reimer, Richards, Scott, Southon, Turney, Wacker, Adolphi, Büntgen, Capano, Fahrni, Fogtmann-Schulz, Friedrich, Köhler, Kudsk, Miyake, Olsen, Reinig, Sakamoto, Sookdeo and Talamo2020]).

Bayesian statistics are the best tools to establish the temporality of archaeological sites (Bronk Ramsey Reference Bronk Ramsey2008, Reference Bronk Ramsey2009). Despite the limitations implicit in the method, they are able to establish estimates and precise interpretations of chronological events (Buck et al. Reference Buck, Cavanagh and Litton1996). In the case of megalithic tombs with different processes of building, modification of the structures and a succession of collective burials, the application of Bayesian models can determine the chronology of the building phases, periods of funerary or ritual activity, times of the start and finish of activity, hiatuses or periods of disuse, and the duration of each phase.

Two control parameters must be met to construct robust chronological models. The first is the need for a correct and re-constructible archaeological record. At the Los Llanetes megalithic cluster, the stratigraphic-structural sequence is known exhaustively and the architectural changes in the monuments have been documented precisely. The second is to obtain Bayesian models with high correlation indices in order to reduce the probability intervals of the chronometric distribution of the dates.

The chronological sequence has been created with two Bayesian models using OxCal: models by phases and the probabilistic estimate of the duration of events. Thus, two models of phases have been made according to their stratigraphy, grouping the dates in the construction levels and different areas depending on architectural and/or activity phases. First, a model of phases in Dolmen 1 has been generated, since this is the monument with the largest number of dates for superimposed stratigraphic-structural contexts that has provided dates for all the phases, enabling a robust chronological sequence to be established. Second, a model of phases for the four monuments has been determined using the 26 dates that cover the chronological development of the megalithic group from the Late Neolithic to the Late-Final Bronze Age. The single date in the Iron Age has not been used as it is the only date for this phase and reflects a long discontinuity or hiatus after the older dates and does not provide a temporal range defined by start and finish boundaries.

In both models, correlation indices (A_model) of above 60% were obtained, as required by Bayesian statistics (Bronk Ramsey Reference Bronk Ramsey1995). These statistical indices confirm the correct correlation of the intervals and probabilistic distribution of the dates with the stratigraphic sequences. This has enabled the determination of the chronological events of construction, transformation and funerary or ritual activity in the megalithic cluster, as well as the temporality and duration of the phases with the chronological boundaries of their start and finish.

The duration of the activity was obtained with the Span function in OxCal (Bronk Ramsey Reference Bronk Ramsey2009) to determine the chronometric time in years of the phases of use of the megalithic structures. Complementary with this, the sum of probabilities (Bronk Ramsey Reference Bronk Ramsey1995, Reference Bronk Ramsey2009) has allowed the intensity and duration of the activity and the presence of hiatuses between the phases to be assessed. Finally, the contemporaneity test (χ 2 test) (Ward and Wilson Reference Ward and Wilson1978) has been performed by combining the three dates for Phase 5 in Dolmen 1 using the Combine function (Bronk Ramsey Reference Bronk Ramsey2009) in order to verify if the activity in this period took place in close, short-duration time intervals.

The complexity of the architectural sequence at the megalithic site, the variety of contexts and uses, the type of sampling and the limited number of dates obtained in the present study mean that we must be prudent in the interpretation of the Bayesian models. It is not feasible to reach definitive inferences about the chronologies owing to the limitations of the study as regards the record itself and the samples that were obtained. The first limitation is the impossibility of obtaining samples to date the full stratigraphic sequence in each tomb, as not all the phases could be dated. The second constraint is the low number of dates obtained corresponding to Prehistory, especially in Dolmen 2, which reduces the potential for the construction of solid Bayesian models and defining the temporal boundaries of the phases and hiatuses more precisely. The third reservation is determined by limitations of the statistical analysis itself, such as the sum of probabilities, because the results of the probabilistic estimates depend on the number of dated samples and the extension taken by the calibration curve (Michczyñski and Michczyñska Reference Michczyñski and Michczyñska2006; William Reference William2012).

The contextualized analysis of the El Pozuelo complex in relation to the diachronic sequence of dolmens in southwest Iberia has been carried out by calibrating the 152 radiocarbon dates, using the sum of probabilities and Bayesian models developed by architectural groups.