Iron Age combustion structures in the north-eastern Iberian Peninsula: an interdisciplinary experimental study

Archaeological and Anthropological Sciences https://doi.org/10.1007/s12520-023-01772-x (2023) 15:76 RESEARCH Iron Age combustion structures in the north‑eastern Iberian Peninsula: an interdisciplinary experimental study Maria Carme Belarte1 · María Pastor Quiles2 · Marta Mateu3 Alessandra Pecci6 · Sílvia Vila7 · Ada Gomar4 · Marta Portillo4 · Carme Saorin5 · Received: 1 December 2022 / Accepted: 14 April 2023 © The Author(s) 2023 Abstract The aim of this research is to investigate the efficiency of combustion structures, the fuels used, the structure maintenance and the range of related domestic activities. An experimental programme was carried out in which replicas of archaeological Iron Age combustion structures were put to work. Based on the available archaeobotanical records, various fuel types (wood, grasses, palm leaves and animal dung) were used. Variables such as increased heating and times were measured in order to determine whether variations occurred depending on the fuels used, the type of structure, the location, or the weather condi‑ tions. The possibility of their use for cooking was also tested. A combination of methodologies was applied for integrated analyses: anthracology, phytoliths, calcitic microfossils, Fourier transform infrared spectrometry, micromorphology and chemical analysis of hearth surfaces. Observations and data recorded during the experimental tasks, together with the results of the interdisciplinary analyses, contribute to a better understanding of the Iron Age archaeological combustion structures. Keywords Iron Age · Western Mediterranean · Archaeological science · Experimentation · Hearths 2 University of Alicante and ICAC (Catalan Institute of Classical Archaeology), Tarragona, Spain Maria Carme Belarte 3 ICAC (Catalan Institute of Classical Archaeology), 2021 BP 00103, Tarragona, Spain Marta Mateu 4 Department of Archaeology and Anthropology, Archaeology of Social Dynamics (SGR‑Cat 2021‑501), Institució Milà i Fontanals (IMF), Spanish National Research Council (CSIC), Barcelona, Spain 5 Department of History and Archaeology, GRAP (Grup de Recerca en Arqueologia Protohistòrica), PGC2018‑099579‑B‑I00, IAUB (Institut d’Arqueologia de La Universitat de Barcelona), Barcelona, Spain 6 ERAAUB, Department of History and Archaeology, INSA‑UB, IAUB (Institut d’Arqueologia de La Universitat de Barcelona), Barcelona, Spain 7 University of Lleida, Lleida, Spain * María Pastor Quiles Marta Portillo Carme Saorin Alessandra Pecci Sílvia Vila Ada Gomar 1 ICREA (Catalan Institution for Research and Advanced Studies) and ICAC (Catalan Institute of Classical Archaeology), Tarragona, Spain 13 Vol.:(0123456789) 76 Page 2 of 25 Archaeological and Anthropological Sciences (2023) 15:76 Fig. 1  a Map of the study area with the location of the Ciutadella Ibèrica de Calafell archaeological site; b one of the streets of the reconstructed site, which is also an experimental archaeology centre Introduction This paper addresses experimental archaeology related to the fire structures built and used during the first millen‑ nium BC in the north-eastern Iberian Peninsula. The Iron Age settlement pattern in the study area is characterised by agglomerated sites. The houses were arranged sharing party walls built with stone and earth and roofs that con‑ sisted of a layer of earth on a bed of branches supported by wooden beams (Fig. 1b) (Belarte 2008). Combustion structures are well preserved at many archaeological sites from this period (Fig. 2) (Belarte et al. 2016), especially compared to those from previous chronologies. These structures show a diversity of morphological characteris‑ tics built with different materials and techniques (Belarte 2021; Belarte et al. 2022). In the framework of the project “Transdisciplinary and experimental study of firing struc‑ tures in the Western Mediterranean during protohistory (first millennium BC) (TRANSCOMB)”, we are conduct‑ ing interdisciplinary analyses to gain a better understand‑ ing of these structures (Belarte et al. 2023). In this field of research, certain questions have arisen and remain open. Do the different traits of the combustion structures, especially the preparation layers, result in longer firing times and/or higher temperatures? Therefore, could their use have been intended for that purpose? Regarding fuels, were the different types and plant species used for Fig. 2  Example of an Iron Age hearth, Barranc de Gàfols (Ginestar, Tarragona), sixth century BC 13 Archaeological and Anthropological Sciences Page 3 of 25 (2023) 15:76 76 Table 1  Experimental combustion structures Com‑ bustion structure Location Shape Preparation layer Measures Features Hearth 1 Hearth 2 Indoors Indoors Quadrangular Quadrangular Mudbrick infill Pottery sherds 116 × 120 cm 50 × 50 cm Hearth 3 Hearth 4 Indoors Outdoors Oval Oval Pebbles None 63 × 57 cm 80 × 60 cm Hearth 5 Hearth 6 Oven Outdoors Rectangular None 72 × 52 cm Indoors Quadrangular Pebbles and pottery sherds 63 × 51 cm Outdoors Oval ground plan, vaulted None 150 × 60 cm Earthen border of 20 × 11 cm. Mudbrick infill Excavated in a shallow pit 6–7 cm in depth. Earthen border with vegetal temper Excavated in a shallow pit 8 cm in depth Directly on the ground, an earthen layer of 1.5 cm Excavated in a shallow pit 7 to 15 cm in depth Earthen border 6–8 × 9 cm Mudbrick structure, covered with mud mixed with vegetal temper different objectives? And how was smoke removed in the case of indoor fires? Regarding the specific use of hearths and ovens, is it possible to confirm their domestic or culinary functions? To answer these questions, we have implemented an inter‑ disciplinary methodology, which also has the objective of testing the suitability and limits of the different techniques. An important part of the methodology consists of an experimental archaeology programme. It has been carried out at the Iberian Citadel of Calafell (Tarragona, Spain), an Iron Age site dating from the sixth to the first centuries BC (Pou et al. 2001) that has been reconstructed and is open to visitors. It is also an experimental archaeology centre (Fig. 1). The experimental programme includes the following stages: the design of combustion structures of diverse types (with different building materials and techniques), building them in different locations (interior/exterior), firing and data collection, sampling and analyses and comparison with the archaeological data. We selected two experimental structures, one indoors (Hearth 2) and one outdoors (Hearth 4), to present and dis‑ cuss the results obtained from the interdisciplinary analyses. Our aim was to obtain a better understanding of the data recovered from the archaeological structures. Materials and methods Experimental combustions and fuels This experimentation was carried out in three different peri‑ ods between 2021 and 2022 (June 2021, November 2021 and May 2022) to compar (...truncated)