The building stone of the Roman city of Lixus (NW Morocco): provenance, petrography and petrophysical characterization

Abstract

The characterization of building materials is a key tool to assess deterioration processes and improve potential restoration works of archaeological sites. The aim of this paper is to identify and characterize the most important building stones used in the construction of the Roman city of Lixus (Larache, Morocco) by means of petrographic and petrophysical techniques. Based on the visual analysis of the monuments, three major building stones (i.e. lithotypes) have been identified: i) Oligocene sandstones, ii) Quaternary sandstones and iii) Quaternary conglomerates. Based on the analysis of the regional geology and exploitation marks, these three lithotypes have been recognised to crop out in the surroundings of Lixus and the quarries, presumably Roman in origin, recognized. The Oligocene sandstone is the primary building stone in Lixus as it forms and crops out extensively in the Tchemmis hill, at the top of which the city is settled. The Quaternary sandstones and conglomerates, which represent nearshore deposits and eolianites, crop out along the Atlantic coast where they form part of the cliffs next to Larache. Petrographic results indicate that lithotypes differ notably in grain size, ratio of detrital to allochemical components, and the configuration of their porous system. Mechanical analysis shows that the Oligocene sandstones are more resistant to compression than the Quaternary sandstones and conglomerates, the latter exhibiting relatively low compressive strength. The Oligocene sandstones, which display scarce porosity and permeability, show a hydric behaviour characterized by a very low degree of absorption and desorption water, likely resulting from a poor connectivity of the pore network. Contrary to the latter lithotype, the Quaternary sandstones, which exhibit very high porosity and permeability, display a hydric behaviour characterized by high degree of both absorption and desorption of water. This is attributed to the low degree of cementation compared to porosity of this lithotype and the excellent connectivity of the porous network. Finally, Oligocene and Quaternary sandstones do not show a significant weight loss after the accelerated artificial aging test, indicating that both are slightly affected by salt crystallization and presumably ice formation. Results indicate that the relatively fine state of conservation of the building rocks of Lixus is linked to intrinsic factors such as mineralogy and petrophysical characteristics together with the favourable effect of the climatic condition of the study area.

Characterization, Analysis, and Investigation of the Provenance of the Stone Construction Materials of the Vera Cruz Church (Segovia, Spain)

“…Complementary to the use of these mineralogical, petrographic, and chemical techniques, other authors have worked on the comparative study with petrophysical tests, mainly focusing on hydric [18] and mechanical properties through non-destructive testing [19], and even through the correlation of deterioration patterns in the monument and in the quarries [20,21]. In our work, we offer a multi-analytical study with an important presence of SEM-EDX observations to complement the petrographic discussion.…”

Upper Cretaceous Limestones as Stone Resources for the Monuments of Oviedo (Asturias, NW of Spain): Petrographic Variability and Stratigraphic Origin

“…Stone material undergoes alteration processes when exposed to the elements (Martínez-Martínez et al 2017;Damas Mollá et al 2018;Sitzia et al 2021), and if the damage is significant, the stone must be replaced to prevent further deterioration and the ruin of the building. In these cases, it is convenient to know the origin of the material: the geographical and geological location of the lithotypes, the exact formations, or even outcrops of origin (Fronteau et al 2010;Bone 2016;Carter et al 2017;Ajanaf et al 2020). This information will make it possible to locate a stone that is similar to the original in characteristics and properties and, so, in behavior (Bugini and Folli 2008;De Kock et al 2015;Zoghlami et al 2017;Anania et al 2012;Forestieria and Álvarez de Buergo 2019), and to find the most suitable material to replace ashlars or other construction elements in heritage restoration works.…”