Petrographic identification and physical behavior of building materials in the archeological site of "Banasa" (Morocco)

Abstract

The archaeological site of "Banasa" is a historical heritage which is an asset of cultural tourism in the region of
Gharb (Morocco). A petrographic characterization was carried out for the building materials of the site, and for the
lithofacies which resemble to those of "Banasa" and come from geological formations close to the site. Comparison
of the results allowed us to identify the different lithofacies of the site, found in majority to be sedimentary rocks,
originated from well known geological formations of which we have determined the locations in this study. The three
most abundant lithofacies are i) calcarénites from Bouknadel, ii) Biocalcarenites from Lalla Zahra, and iii) quaternary
sandstone from the Gharb. A study of the physical behavior (density, porosity, water absorption, permeability and
resistance to salt crystallization) of these three most abundant lithofacies was performed. The results showed that
the calcarénites and the Biocalcarenites hold more porosity (respectively 16.76% and 14.87%) than the sandstones
(8.82%). According to the salt crystallization tests, the sandstone samples have lost more than 10% of their weight,
which means, that these sandstones have a low resistance to the salt crystallization than that of the two others
lithofacies. This is likely a direct result of the pore size, which is smaller in the case of sandstones. The valuable
results obtained in this study will serve as a database for a future restoration of the site, and to ensure a better
preservation of this heritage.