Archaeometric characterization of Early Bronze Age building materials in the Iberian Peninsula. An example from Central Spain, the Bocapucheros site (Almagro, Ciudad Real)

Abstract

This study provides a thorough characterization of the stone and earth-based construction materials from the Bronze Age funerary site of Bocapucheros (Almagro, Spain), emphasizing their composition, structural roles, absolute dating (14 C) and degradation processes. The load-bearing system consists exclusively of masonry walls built with locally sourced quartzitic blocks, shaped and assembled using manual techniques. Structural elements, including lintels and corbelled vaults, display different types of fracture modes caused by long-term mechanical and environmental stresses. Despite these damages, the overall stability is preserved thanks to a robust design that effectively distributes compressive loads. A multi-phase construction sequence is proposed, encompassing site preparation, foundation laying, wall assembly, and corbelled pseudo-dome roofing. The mortars are earth-based, primarily composed of aluminosilicate clays such as muscovite and kaolinite, combined with varying proportions of quartz aggregates, alongside traces of carbonates and iron oxides. Analyses performed using radiocarbon dating, X-ray diffraction, Fourier-transform infrared spectroscopy, Raman spectroscopy, X-ray fluorescence, and backscattered electron microscopy coupled with energy-dispersive X-ray spectroscopy confirm the compositional diversity and the presence of volcanic and metamorphic components consistent with the local geological context. Thermogravimetric and calorimetric data reveal dehydration and decarbonation processes aligned with the behavior of clay minerals and carbonates. This integration of mechanical resilience, material heterogeneity, and advanced corbelling techniques reflects sophisticated architectural knowledge within Bronze Age society. These findings advance the understanding of prehistoric construction technologies and support ongoing efforts in cultural heritage preservation.