Soil Data Comparison in the Old vs. Restored Sections of the Bam Citadel Archeological Site in Kerman, Iran

Soil data can be very significantly informative in archeological and anthropological studies. Bam Citadel (BC), as the largest and oldest earthen (non baked brick) monument of the world has been restored for several times, but no data have yet been available surrounding the materials employed in the restoration work. Bam Citadel (BC) was almost totally destroyed by the severe earthquake of December ۲۶th, ۲۰۰۳. A detailed knowledge concerning the old sun-dried cobs and the architecture of the exposed parts could be essential for a better ongoing as well as future restoration. Some old parts of the citadel have been exposed following the devastating earthquake. A micromorphological, physico-chemical, mineralogical and sulfur isotope geochemistry study was carried out to compare the characteristics of the soil samples obtained from the previously restored vs. those of the exposed old parts of the BC. The results indicated that the electrical conductivity differs widely between the samples obtained from the exposed old parts and those obtained from the restored parts (۶.۴ dS m-۱ and ۴۲.۴ dS m-۱ respectively). This indicates that a saline soil (EC ۴۲.۴ dS m-۱) has been used in the recent restoration work, while the old non saline cobs’ building material, used by original builders, are thought to have been brought from other non saline areas. Smectite, illite, kaolinite and palygorskite were determined as the predominant clay minerals. Massive microstructure was found as dominant in all the samples, but igneous microlites and gypsum crystals were observed only in the repaired parts. The soil matrix from the old parts was found to be high in organic matter.

Keywords:

Bam Citadel , Central Iran , Kerman , Micromorphology , Soil mineralogy , Sulfur geochemistry