=Paper=
{{Paper
|id=Vol-2024/IberCrono_21
|storemode=property
|title=Radiometric dates from open-air archaeological contexts: El Mazo de la Castañera (Fechas radiométricas de contextos arqueológicos al aire libre: El Mazo de la Castañera (Cantabria, España))
|pdfUrl=https://ceur-ws.org/Vol-2024/IberCrono_21.pdf
|volume=Vol-2024
|authors=Eduardo Carmona Ballestero,Cristina Vega Maeso
}}
==Radiometric dates from open-air archaeological contexts: El Mazo de la Castañera (Fechas radiométricas de contextos arqueológicos al aire libre: El Mazo de la Castañera (Cantabria, España))==
https://ceur-ws.org/Vol-2024/IberCrono_21.pdf
Radiometric dates from open-air archaeological contexts:
El Mazo de la Castañera (Cantabria, Spain)
Eduardo Carmona Ballestero (1), Cristina Vega Maeso (2)
Servicio Territorial de Cultura de Valladolid. Junta de Castilla y León
(1) educarmonabal@gmail.com, (2) cvegamaeso@gmail.com
Abstract. This work is focused on a project developed on El Mazo de la
Castañera (Cantabria, Spain). The site is located in a temperate and humid
region, with permanent vegetal coverage that limits observation of superficial
evidence. In consequence there is a lack of open-air habitats: a problem linked
to the low visibility of archaeological remains. For this reason, different
methods should be used. Geophysical survey allows detecting non-visible
archaeological evidence. After that, in order to check the accuracy of method
a trial excavation was conducted in 2014 and 2015. Results were positive:
open-air structures with organic fillings (charcoal and several planks in
vertical position) have been discovered. Radiocarbon dating (AMS) provides
a set of dates from Late Antiquity to Middle Age.
Fechas radiométricas de contextos arqueológicos al aire libre: El Mazo
de la Castañera (Cantabria, España)
Resumen. Este trabajo se centra en un proyecto desarrollado en El Mazo de
la Castañera (Cantabria, España). El sitio está ubicado en una región templada
y húmeda, con cobertura vegetal permanente que limita la observación de
evidencias superficiales. En consecuencia, existe una falta de hábitats al aire
libre: un problema vinculado a la escasa visibilidad de los restos
arqueológicos. Por esta razón, deben utilizarse diferentes métodos. La
prospección geofísica permite detectar evidencias arqueológicas no visibles.
Posteriormente, para comprobar la exactitud del método, se realizó una
excavación de prueba en 2014 y 2015. Los resultados fueron positivos: se han
descubierto estructuras al aire libre con rellenos orgánicos (carbón vegetal y
varias tablas en posición vertical). Radiocarbon dating (AMS) provee un
conjunto de fechas desde la Antigüedad Tardía hasta la Edad Media.
1 Introducción
El Mazo de La Castañera is located in Obregón (Fig. 1), municipality of Villaescusa (Cantabria, Spain). It is a small hill
where alternates layers of clay and limestone cliffs in which are located caves and rock shelters. In some cases have
archaeological remains from Paleolithic to Late Antiquty [Gom72, Rin82, Rui90, Ser01]. On one of them, El Abrigo de la
Casteñera, it has been conducted a research project directed by one of us (CVM). In fact, the results of the project have
reinforced the known information, providing well contextualized data which have proved an intensive occupation from
Neolithic to Bronze Age. To solve some specific issues related to this project have been carried out 4 fieldwork campaigns
in the outer space near El Abrigo de la Castañera. Some of the results of this work are presented here.
Figure 1 - Location of El Mazo de La Castañera
2 Objetives
The mentioned research project aimed to explore the potential archaeological record located on the nearby of the Abrigo
de la Castañera. Especially data about open-air habitat were necessary because there is a notorious absence of this kind of
sites in the Cantabrian region. The lack of habitats is linked to the low visibility of archaeological remains related to
peasant communities from recent Prehistory (post holes, pits, thin deposits, etc.). These kinds of remains are difficult to
detect with traditional survey because the environment has permanent vegetation coverage. In consequence, a different
method should be employed.
3 Methods
3.1 Geophysical survey: Zone M1
In order to detect non-visible evidence a geophysical
survey was conducted in El Mazo de la Castañera
[Car16]. To get data the procedure employed was an
electromagnetic induction survey. We worked on a 9 ha
area divided into 6 different zones (M1 to 6) (Fig. 2). The
data and its interpretation are presented by georeferenced
surface maps. These maps provided images of some
anomalies after we have analyzed and have processed the
data. The aim of this method is to distinguish evidences of
abnormal accumulations embedded into non-anthropic
sedimentary soils. To cover the whole area with optimum
quality and data density, we needed hike through the
study area doing perpendicular tracks (1 meter between
them). In consequence, we have obtained a mesh of each
zone. Regarding available data about archaeology and
geology, we have worked with a frequency that allowed
collect data to 2.5 meters of depth. The purpose was to
explore only the superficial layer where archaeological Figure 2 - Surveyed zones on El Mazo de la
evidences should be found. The selected frequency was Castañera
47.175Hz, both electric and magnetic.
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Results were represented in two types of georeferenced surface maps: Electric conductivity (EC) and magnetic
susceptibility (MS). These maps show surface anomalies which were detected after data analyzing and processing. The
results show several potential evidences. More precisely, there are traces of anomalies which have some kind of
geometrical design or sedimentary filling with archaeological potential. The detection of non-angular structures, with low
intensity, is pretty difficult. Therefore, we had to present the results with high contrast in order to observe these traces. The
results were different between zones. The most interesting were located in M1, M4 and M6. They show circular anomalies,
with several sizes, that are gathered in some specific areas. It was also documented huge sedimentary packages with a high
archaeological potential in several cave mouths. M1 shows several anomalies with geometrical shape (Fig 3), besides big
sedimentary acumulations nearby rock shelter of Abrigo de la Castañera were detected. The most significative anomaly is
a sedimentary rounded zone with a dark perimeter, and with a small anomaly in its centre.
Figure 3 - Surface maps from M1 Zone: Magnetic Susceptibility (MS)
3.2 Exploring and checking anomalies
The anomalies detected suggest that it is possible to find archaeological structures related to open-air domestic zones. The
research has documented several "hot spots" where we have focused the next step of research. In 2014 and 2015 we have
conducted an archaeological excavation in zone M1 in order to check readings (Fig. 4). To do that, a 50m2 trial excavation
was opened. Underneath of 90 cm of quaternary fillings (SU 1) there were SU 2 and SU 10, reddish deposits with
abundance of charcoal and a sporadic presence of small and rounded sherds of pottery. Also a few lithic artefacts were
recovered. Covered by SU 2, several features have been discovered: a pit, postholes and a ditch with several planks in
vertical position, filling by the same stratigraphic unit (SU 4). SU 10 (partially excavated) covered a couple of postholes.
It cannot determinate yet if archaeological evidence discovered is related to a dwelling or another kind of feature like a
fence, a corral, etc. Nowadays the study of archaeological record from zone M1 is ongoing. For instance, we are waiting
for results of several analytics (micromorphology, anthracology …). All of them will provide interesting data in a near
future.
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Figure 4 - Archaeological excavation in zone M1
3.3 Radiocarbon dating
Since short-lived samples were not available, several samples of charcoal and sediment were dated by AMS
radiocarbon dating. Samples were sent to the International Chemical Analysis form the University of Miami. Dates were
calibrated with Oxcal 4.2.3 using ItnCal13 calibration curve [Rei13].
Samples were from different archaeological contexts (Table 1, fig.5). Results provided a set of dates from Late
Antiquity and Middle Ages, which are unusual in Cantabria because dating from “modern contexts” is quite uncommon.
289
Table 1 - Radiometriac dates from El Mazo de La Castañera
ICA ID Date B.P. Date Cal AD (2σ) Material Context Age
14C/1117 1450,40 545 (95.4%) 656 AD Charcoal SU 2, sample 6 Late Antiquity
15C/0255 940,40 1019 (95.4%) 1184 AD Charcoal SU 2, sample 8 High Middle Age
1041 (35,9%) 1108 AD Charcoal SU 4, sample 1, High Middle Age
16C/0858 890,30
1116 (59,5%)1218 AD bottom of pit
Charcoal SU 4, sample 2, High Middle Age
16C/0859 930,30 1025 (95,4%) 1165 AD
plank
773 (71,8%) 906 AD
16C/0860 1160,40 Sediment SU 10 Early Middle Age
916 (23,6%) 968 AD
Figure 5 – Sampled contexts
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4. Discusion
If we analyze the determinations according to their arcaheological context, we observe that, on the one hand, deposits
seem to correspond to two different phases linked to the Early Middle Ages (SU 10) and the High Middle Ages (SU 2 and
features that covers) (Fig. 5). On the other hand, the northern area of activity (configured by SU2 and features) picks up
the most modern and the oldest dates. Given the type of sample, it is highly likely that the explanation is related to the "old
wood effect" linked to the sample 6. On this subject, the ongoing anthracoligic analysis may provide relevant information.
Consequently, this date should not be taken into account for the purpose of determining the date of the stratigraphic event
where it is located. In order to fine-tune the dating of this area of activity, the SU 2 and SU 4 (158C/205; 16C/858 y
16C/859) have been combined in Oxcal. The result (Fig. 6) is a coherent date: 1039 (95.4%) 1163 cal AD. That is, the
formation of these events is circumscribed in this case to the High Middle Ages.
Figure 6
Figure 7
5 Conclusions and perspectives
The research has demonstrated that the anomalies detected may correspond to truly archaeological open-air structures. The
function of the structures is still unknown, although they seem to be linked to a domestic use, highly probably agricultural
use. It has been necessary to excavate 90 cm of fillings to reach the contexts, which shows even more the difficulty of
detecting this type of evidence in Cantabria.
In sum, the results of the project can be considered positive and promising. Beyond the lack of monumentality of
evidence, the importance of the results lies in the unusual of them within an archaeological framework in which these kind
of contexts are scarce, specially to the period to which they belong.
291
Acknowledgements
This research has been funded by Government of Cantabria, which has been supported the project Electromagnetic Survey
for the Location of Archaeological Structures in El Mazo de La Castañera (Obregon, Villaescusa) in 2013 and the project
Locating open-air habitats from recent Prehistory in El Mazo de la Castañera (Obregón, Villaescusa) from 2014 to 2016.
References
[Car16] Carmona Ballestero E., Vega Maeso C. López Jiménez O., Martínez Calvo V. (2016) Geophysical survey on “El
Mazo de la Castañera” (Cantabria, Spain): looking for open-air domestic remains. In: Kamermans, H., de Neef,
W., Piccoli Ch. (eds) The Three Dimensions of Archaeology: Proceedings of the XVII UISPP World Congress (1–
7 September, Burgos, Spain). Volume 7/Sessions A4b and A12, Archaeopress. Pp. 133-139.
[Gom72] Gomarín Guirado F. (1972-73) Dos nuevos yacimientos de la Edad del Bronce en la provincia de Santander,
Zephyrus, XXIII-XXIV, pp. 193-95.
[Rei13] Reimer P. J., Bard E., Bayliss A., Beck J. W., Blackwell P. G., Bronk Ramsey C., Grootes P. M., Guilderson T. P.,
Haflidason H., Hajdas I., Hatte C., Heaton T. J., Hoffmann D. L., Hogg A. G., Hughen K. A., Kaiser K. F.,
Kromer B., Manning S. W., Niu M., Reimer R. W., Richards D. A., Scott E. M., Southon J. R., Staff R. A.,
Turney C. S. M., van der Plicht J. (2013). IntCal13 and Marine13 Radiocarbon Age Calibration Curves 0-50,000
Years cal BP. Radiocarbon, 55(4).
[Rin85] Rincón Vila R. (1985) Las Culturas del Metal. In: García Guinea M. A. (ed.) Historia de Cantabria. Prehistoria,
Edades Antigua y Media, Estudio, Santander. Pp. 113-209.
[Rui96] Ruiz Cobo J. (1996) El Abrigo de La Castañera (Obregón, Villanueva de Villaescusa): materiales arqueológicos,
Boletín Cántabro de Espeleología, 12, pp. 123-28.
[Ser01] Serna Gancedo M. L., Valle Gómez Á. y Obregón Goyarrola F. (2001) Las cuevas del valle de Villaescusa.
Asociación para la Defensa del Patrimonio de Villaescusa, Santander.
292