Özet:

The purpose of this study is to investigate lithological characteristics and the origin of the columns used in the historical buildings of Diyarbakır Old City. Totally 24 buildings 7 churches, 9 mosques, 2 hans, 4 traditional Diyarbakır houses and two towers on the city wall are investigated for this purpose. The study is focused only on the cylindrical rock columns and their architectural features, locations and functions in the building are not considered. The richest building of the study is the Great Mosque with 49 columns.Total number of columns investigated in the Old City is 230, 106 of these columns belong to basalt, 102 to limestone and 9 to meta-ophiolites. Other 6 columns are made up of limestone-basalt alternating rings and 7 are mixed columns composed of meta-ophiolites and limestone.According to the petrographic analyses of 24 samples collected from the Great Mosque and hans’ columns, the lithologies of 6 columns are serpentinized peridotite, 5 are nummulites-bearing limestone Eocene , 5 are reef limestone Miocene and 8 are olivine basalts. Following results are derived for the origin of these columns considering geological map of the area and the data published in the literature: 1 Meta-ophiolites are used only in ten columns of the Great Mosque. The source rocks of these columns can be observed along the thrust zone located to the north of Diyarbakır, however the particular quarries of these columns are not so far known, 2 Eocene limestones are characterized by high porosity and low strength and are used only in ten columns of the Great Mosque. There are several potential quarries of this lithology in the close vicinity of Diyarbakır, 3 Miocene limestones and basaltic rocks have similar physical properties and are the most preferred rock types of the columns observed in almost all buildings. Most of the present quarries for producing building material around Diyarbakır belong to these two rock types

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